Compressing background, function of sensor size?

Discussion in 'Nikon' started by brian_hooks, Nov 24, 2011.

  1. Hello all,
    Lately I have been exploring compressing the background in shots by using longer lenses. I currently shoot Nikon D300s and have been using my 80-200 (push pull) lens. I really like the effect but I find that many times I cannot get far enough away from my subject to get anywhere near 200mm where the greatest compression would tend to be. My question is would someone shooting say a D700 or D3 full frame camera have the same amount of compression at the same distance or would the crop sensor magnify the compression just as it does the effective reach of the lens. For example would a shot taken with a crop sensor camera at 200mm have the same compression effect as one taken at 300mm on full frame? I hope I'm explaining my question correctly. Just trying to understand the physics.
    Brian
     
  2. [​IMG]Example...
     
  3. Focal length being constant, field of view becomes narrower as sensor size decreases: but depth of field is not affected.
     
  4. The way you are using the work "compression" is perspective. Perspective is not DOF. Perspective is controlled by the distance between the subject and the camera. Nothing else. Sensor size and focal length will effect image size and field of view (FOV), but not perspective.
     
  5. The word "compression" has been used to refer to the fact that distant objects seem to be on much the same plane as one another when photographed with a lens of long focal length. Here, however, it seems to mean something else: "I cannot get far enough away from my subject...". This is confusing. I'd like to see a photo taken from not "far enough away". That should help in understanding the problem.
     
  6. Agree 100% with Bruce. It's a matter of your distance to the
    subject - perspective. So going FX would not make a
    difference, if you stay at the same spot and change focal
    length to have the same composition with your main
    subject, i. e., field-of-view.
     
  7. The larger sensor wouldn't change the relationship between you, your subject, and the background unless you move. And to get your subject to fill the frame the same way, using the same focal length, you'd have to move closer to the subject (while using a larger sensor), and thus increase the perspective effect (making the background less "compressed" and close-in to your subject).
     
  8. Shooting longer focal lenghts on larger formats, you get the same field of view and perspective, but a shallower DOF at the same f-numbers.
     
  9. "With longer focal lenghts on larger formats, you can get the same field of view and perspective, but a shallower DOF at the same f-numbers" - Not quite. Once you get the same field of view on large sensor, by cropping, you get the same DOF as in the small sensor camera.
    If you compare small and large sensors complete pictures with te same distance and focal length, you get different DOF, just because you measure DOF at two different areas, where lens sharpness differs the most at edges of FX sensor.
    If you consider DOF over common picture area in small and large sensors, then Mukul Dube is correct. The lens sharpness property does not change with the sensor size. What changes is how you measure DOF on small and on large sensor, and your perception of sharpness.
     
  10. "Once you get the same field of view on large sensor, by cropping, you get the same DOF as in the small sensor camera."

    Not in my experience. Check the pics below; first, the DX one, shot at a FL= 35mm. Second the FX one, FL= 55mm (I know the FX should have been shot with a FL of 35x1.5= 52.5mm, but I dont have such lens). Both at the same distance, f2.8.
    The difference is 1.5 times more DoF (roughly) for the DX lens. It`s not a huge difference, but it can be noticed at the Air Duster can or in the "seconds" watch marks.
     
  11. DX shot:
    00ZeNp-418803584.jpg
     
  12. FX shot:
    00ZeNq-418803684.jpg
     
  13. Depth of field is determined not by field of view but by focal length (see my first post here). For the same field of view, a smaller sensor will use a shorter focal length, which will of course give more depth of field.
     
  14. Perspective is not DOF, but I tried to achieve large DOF by focus bracketing with a 100 mm lens on a crop body and the effect is similar. I do not know whether this is what you are after.
     
  15. "Depth of field is determined not by field of view but by focal length... "
    Right; but I`d better say that is determined by magnification (instead of focal lenght) and aperture.
    About your first post,
    "Focal length being constant, field of view becomes narrower as sensor size decreases: but depth of field is not affected... "
    Exactly; if you don`t change your focal lenght, nor your shooting distance, there is no change at all (magnification remains the same). You only get a "cropped" frame with a smaller camera (or a larger frame with a bigger camera).
    "For the same field of view, a smaller sensor will use a shorter focal length, which will of course give more depth of field."
    I assume that you don`t change your shooting distance, hence with a shorter lens you get smaller magnification, then larger DoF.
     
  16. The degree of compression (or perspective) is the same with the same subject to camera distant regardless of focal length. However, the framing is different for fx or dx camera and thus photographing an object at the same distance. The 300mm lens on fx camera would give you very much the same photo as a 200mm lens on dx camera.
     
  17. Sorry, apparently the image I was trying to post is too large and I'm not certain of how to make it small enough to fit, but in essence my question was that in the shot i was trying to take I wanted to shoot at or near 200mm to compress the image as much as possible and bring the background in closer but I was limited in how far I could back away from my subject and thus the amount of zoom I could use. It had occured to me that a full frame sensor would have less extension (?) than my crop sensor camera which would allow me to shoot the same shot closer to the 200mm max of my zoom. I just wasn't sure if the background would be pulled in the same amount as with the crop sensor camera.
    Hope that helps
     
  18. Frank Skomial [​IMG], Nov 24, 2011; 12:59 p.m.
    "With longer focal lenghts on larger formats, you can get the same field of view and perspective, but a shallower DOF at the same f-numbers" - Not quite. Once you get the same field of view on large sensor, by cropping, you get the same DOF as in the small sensor camera.​
    DOF is the same regardless of sensor size in the same sense that a Kia is as good as a BMW; yes, it is often true on paper. But in practice, it doesn't happen that way. A 50mm lens has less DOF on an FX sensor not because of any magical interations between the sensor and lens, but because the larger sensor requires moving much closer to frame the shot in the same way. Moving closer reduces your DOF; thus, a larger sensor produces a shallower DOF with the same lens.
    I'm going to use 150mm as an example, since I have that range for several cameras. Framing a face to more-or-less fill the frame with that lens on by 4x5 puts me something like two feet away. On my Hasselblad it's closer to 4 feet. With FX it's more like 6, and closer to 10 or 12 with a DX sensor. A quick check with the online DOF calculator tells me that at f/8 I would get a DOF of .07 feet with the 4x5 (just under an inch), while a D300 would give me about a half a foot.
    This is why view camera users need crazy powerful studio strobes - so they can shoot at f/32. Which is still only 3 inches, compared to a couple feet on the Nikon.
    In order for multiple formats to have the same DOF from the same lens with the same composition, they all need to be focused at infinity. In which case, the discussion of DOF is moot.
    Compression is based on the relationship between camera, subject, and background. A wider lens will usually place the subject closer to the camera than the background. A longer lens places the subject closer to the background than the camera, which is what creates the compression effect.
    Picture someone standing 10 feet from a tree. With a fisheye lens, you'll be right on them ... that tree looks like it's way out there, since it's several times further away than the subject. A 300mm lens will require you standing much further away, and suddenly the tree is only 120% as far away as the subject, and they look much closer.
    Compression is also affected by sensor size (since you will have to move to recompose), but it is not the same as DOF. That 300mm lens is going to give you more compression, regardless of whether you shoot it at f/2.8 or f/64.
     
  19. Here's a website with some examples: http://toothwalker.org/optics/dof.html
     
  20. The degree of compression is totally related to the distance from subject. So using a FF camera would not help.
     
  21. The degree of compression is totally related to the distance from subject. So using a FF camera would not help.​
    Using A FF camera would help, in the sense that you would move closing to the subject due to the wider FOV of FF, with respect to the same FL used.
     
  22. I tend to agree with everything Zack is saying. I started into digital photography with a 40D, and when I went to a 5D mkI, I immediately noticed that the depth of field with my 5D was much shallower than using the same lenses on my 40D. Compression is all about focal length. I can shoot with two lenses, say a 50 prime and then my 70-200. Even if if I move back while shooting at 200mm to compose the same shot, the background will appear significantly closer than with the 50mm lens.
     
  23. An image made with a super-telephoto lens makes objects far away and objects nearby appear to be closer together. This is my understanding of "compression". I think it is what the original poser is referring to.

    For example these runners appear to be closer to each other than they actually are. Approximate focal length equivilent is 576MM in this shot.

    http://www.photo.net/photo/11091952
     
  24. J. Harrington, nothing wrong with it; this is certainly a perspective effect. As mentioned, it`s a camera/ subject/ background relationship.
    In the pic you`re showing, there is a large distance between the camera and the subject, but short between the subject and background... here it is a given "compression effect".
    If the photographer have to use a shorter lens to get the "same" picture, a shorter shooting distance must be achieved. The relationship is then changed; the focus distance is shorter, the subject to background (relative) distance is (proportionally) larger... but actually, the picture will never be the "same" because perspective have changed.
    If in the same scenario you simply choose a longer focal lenght, without changing your position nor your camera, you just get the subject bigger on the screen (we could say a "cropped"/tighter framing or narrower viewing angle). Change the format to a larger one, and you will get the very same scene, very same "compression", at a higher magnification.
     
  25. "Compression is all about focal length... "

    Imagine the scene J. Harrinton provides. We are in a stand at the sports stadium; you have two cameras, one with a wide angle (say, 24mm) and the other with a tele (400mm) lens.
    Shoot both cameras at a time. Check the prints; if you enlarge the detail of the the athletes runing in the curve on the 24mm lens` print, you will see that the "compression" is the same on both 24 and 400mm prints, the image is the same... the "only" difference is that the 24mm shot is a much wider viewing angle.
     
  26. If you shoot with from the SAME EXACT location then the perspective is already defined. Thus focal length; color of camera or moon phase do not matter. This was well known 10,000 years ago by most hunters, but somehow many many modern folks like to tie perspective to goofy parameters like focal length. Eons ago the lay caveman did this too. The dumber ones lied perspective to spear size. If you shoot from the SAME EXACT LOCATION the perspective is the same, Thus with a cellphone one has the same perspective as a 8x10 view camera. The cell phone has a focal length of 1 to 2 mm; the 8x10 view camera has lens of 200 to 400mm. Sadly the lay masses equate perspective to focal length, but fail to fathom that THEY MOVE the camera.
     
  27. I've also tested and found less DoF on an FX camera than a DX camera. This makes total sense to me as there is less DoF on my 4x5 camera than my medium format camera, and there was more DoF on my 35mm cameras than my medium format. Sensor size does affect DoF. But, that't not really what the OP was after here.
    Kent in SD
     
  28. Everyone here seems to have bits and pieces of the puzzle correct, and bits and pieces of the OP's original question missing or omitted. Here are the concepts that must be understood to give an accurate answer:
    Concept 1: Focal length has nothing to do with perspective. It's only a matter of distance from camera to subject.
    Tested and confirmed: If you shoot a subject with a variety of lenses from the same distance and crop to the same framing, the perspectives will be the same.
    Concept 2: Depth of field has nothing to do with the camera you are using. Depth of field is determined by focal length, lens aperture, and distance to subject.
    Tested and confirmed: If you shoot with a 35mm lens from 6 inches with the same f/stop on large format, medium format, 35mm/FX, or DX, then crop to the same framing, the DOF is the same.
    Concept 3: Using lenses that produce the same field of view on different format cameras produce different results from the same distance. Because perspective is controlled by the distance from your subject to the camera, your perspective (magnification/compression of the background) will be the same, however because you will be using a different focal length your depth of field will be different (assuming you are using the same f/stop).
    Tested and confirmed: If you shoot different lens/camera combinations to achieve the same framing from the same distance with the same aperture, you will retain the same perspective, but will achieve a shallower depth of field with the larger format medium & longer lens combination.
    So, using the three principles above, we can answer the OP's question.
    Conditions: Subject is a static distance from the camera. Background is also a static distance behind the subject.
    Camera combinations (these are not 100% correct, but since the lens in question has markings for 135mm and 200mm we'll use them since it's nearly impossible to get 133.3mm accurately) :
    D300s with 80-200mm f/2.8 lens zoomed to 135mm @ f/4
    D700 with 80-200mm f/2.8 lens zoomed to 200mm @ f/4
    Since your distance to your subject is static your perspective would not change. (Your background magnification/compression would remain the same assuming the crop was identical) What would change is your depth of field. The background would be slightly blurrier on the D700.
    I hope this helps and eliminates any confusion.
    RS
     
  29. It is very simple so not sure where the confusion is. This is more basic than shutter speed.
    Perspective is obviously independent from sensor/film size and focal length. It only depends on your position relative to the subject (i.e. stand somewhere and look at an object - no combination of camera or lens will see it any different).
    Focal length determines what portion of the image is projected on the sensor/film plane (i.e. now make a little frame with your hands and pull it farther-telephoto or closer-wide_angle to your eye). If you bring your hands all the way until they touch your face where you don't see them anymore you have the eq to 40mm in FF. Wider than that and you will have to rotate your head around and stitch what you see.
    Sensor size determines the cropping on the image plane. (i.e. now from everything you can see through your hands pick just a small section in the center and discard the rest).
    It is not true that with FF you would walk closer to take the picture. If you get closer you would change the perspective and the picture you intended to take will no longer be there.
     
  30. Considering the decade's worth of Photo.net threads I have read; the belief that focal length causes perspective is actually quite common. The average poster believes that focal length causes perspective changes and the trend is worse is a dumbing down trend
     
  31. It is very simple so not sure where the confusion is. This is more basic than shutter speed.​
    The confusion is that not everyone understands the concept of perspective. It comes from a generation of photographers that have learned on zoom lenses because they come with the camera and are easier to use for most situations.
    How perspective works is simple, but unless you are shooting with primes, it can be hard to grasp. It's the reason people, (myself included), use improper terms like "foot zoom" even though I know that changing my position changes the perspective of the image and you can't "zoom with your feet".
    And people still wonder why I suggest a prime lens as your first lens purchase if you want to become a better photographer.
    RS
     
  32. Those people might have magic lenses... I want one.
     
  33. Maybe your comment about zooms is true but still weird since looking through a zoom makes it easy to understand that perspective doesn't change when you zoom in and out. The confusion escapes my understanding.
     
  34. I still don`t see the concepts crystal clear. Please help me if I`m wrong:
    I`d say perspective refers to the relationship between all elements in the space, as seen by the photographer. Not only the camera to subject distance. Matt mentioned it in the first posts. I assume you`re ommiting this to make the concept more understandable.
    We can say that Depth of Field is determined by focal length, lens aperture, and distance to subject... and if we are talking about different cameras, format. Different formats will require different enlargement factors for a viewing distance, where the Circle of Confusion is another unavoidable parameter.
    Focal lenght determines the magnification on the film/sensor plane. Depending on the covering angle, some lenses will project a wider or narrower field over the sensor/film plane. FX have a wider covering angle than DX lenses. As mentioned, if you use a FX lens on a DX camera, what is restricting the portion of the image is the format, not the lens.
    (I don`t want to hijack the OP thread; I think his question has been extensively answered).
    ---
    Edit; for years I have been also confused with the perspective concept. It was drawing, and not making photos where I found the answer. There are not bad students, but bad teachers.
    PNet is a good source where I like to learn.
     
  35. Maybe folks get confused because few took drawing, or read older books on photography.
    The concept of perspective and the concept of DOF are different and should be learned without confusing the two subjects.
    One can shoot the same scene from the same spot with all the different cameras in the world and the perspective is EXACTLY the same.
    If one sits in row 34; seat W one gets the same view of the football field too. Lenses and sensors do not cause compression, your location does to the subject.
    It is basic ratios; how far object A and object B are to the viewing point. If two men are both 6 feet tall; the man twice as far away covers one half the arc angle.
     
  36. Those people might have magic lenses... I want one.​
    Me Too :p
    Maybe your comment about zooms is true but still weird since looking through a zoom makes it easy to understand that perspective doesn't change when you zoom in and out. The confusion escapes my understanding.​
    While looking through a zoom should make it easy to understand that perspective doesn't change, it doesn't always. My reasoning comes from a statement made to me by a professional photographer years ago. I penciled it down in "Understanding Exposure" by Bryan Peterson since it's my go-to when I'm trying to get inspiration.
    "The real difference between professionals and amateurs is an understanding of light, perspective, and your subject's background. Taking someone's photo is easy...taking someone's portrait is entirely different. This is what makes photography art and a professional a professional."
    Jose, I don't think you're wrong. You've added a few wrinkles like CoC which I was hoping to avoid to make the concepts easier to understand. I do like your definition of perspective as well...I am posting while at work, so I've got a few disjointed concepts and would probably have re-worded my post if I was teaching a class...lots of words in only a small amount of time. :D
    RS
     
  37. ...or read older books on photography.​
    Bingo! Before there was an internet and somebody wanted to learn something on there own, at some point they probably bought a book. (The photography book I bought in the late 70's made a very clear illustration of why perspective is strictly a function of camera to subject distance.) Now with the internet lots of folks are more than happy to parrot what some other clueless wanker posted.
     
  38. Clueless Wanker:
    http://photoinf.com/General/Klaus_Schroiff/Perspective.htm
     
  39. Funny. I guess since he omits to say that the changes in perspective are due to his walking closer or farther away (and implies the change in perspective is due to using a different lens) it can be confusing. Especially confusing to those people that think that light curves and never walked around in the real world... Just kidding.
    Those trees must be made out of dark matter to bend light that way... Just can't stop joking about it.
     
  40. His example is like showing 1-> a picture of a person's face and 2-> a picture of the back of the head and explain the differences by saying they were taken with different lenses.
     
  41. Using A FF camera would help, in the sense that you would move closing to the subject due to the wider FOV of FF, with respect to the same FL used.
    Thanks Leslie,
    I think you actually caught on to what I was asking. Still can't afford to go FF but interesting to know how things work.
    Brian
     
  42. "Using A FF camera would help"
    Nope. Same compression... FF will capture more of the surroundings with the same lens (since the crop sensor is discarding part of the image) but compression will be the same.
    Walking closer to the subject with a FF camera will not give you the same picture as using a crop sensor from farther away.
     
  43. Thanks Leslie,
    I think you actually caught on to what I was asking. Still can't afford to go FF but interesting to know how things work.​
    No problem, Brian. In this forum, people often forget the practically side of photography and argue the physics and optics behind it. I just yawn and work with the "magic" sorta speak...
    [​IMG]
     
  44. Richard and Mauro illustrate the idea I mentioned that a Kia may be as good as a BMW on paper, but it isn't really. Both of them made compelling and totally true arguments on page three of this thread that basically boil down to, "perspective and DOF are not affected by lens choice because taking the same image from the same distance at the same aperture, and cropping to the desired composition gives you the same DOF and perspective." On paper this is totally accurate, just as a lighter Kia with a 150 horsepower engine might be as fast as a heavier BMW with a 250 horsepower engine when you work out the power to weight ratio.
    But in the real world, it doesn't work this way. The fact is that unless you can afford to shoot everything with an 8x10 view camera, you can't just, "crop to the desired composition" every time. Those of us without near-limitless funds must rely on a variety of focal lengths to get different compositions, and those different focal lengths change the relationship between camera, subject, and background; thus altering perspective and DOF. Much in the way that a BMW's superior handling allows you do brake less, and the better build quality means that it retains much more horsepower as it ages. In the real world, the BMW is way faster than the Kia, and lenses affect perspective and DOF.
    If it makes you happy to know that the theoretical physics support your argument, then by all means continue. You are, technically, correct. But if you wonder why so many people are posting photos that "disprove" you or can't understand what you're saying, then go test drive a Kia and a BMW.
     
  45. " In the real world, ..........., and lenses affect perspective and DOF."
    No, in the real world your position and distance to subject and background dictate the perspective, your position, however, might be dictated by lens availability, but that is a side issue. Don't confuse the correct physics and understanding of the thing with emotional irrelevancies.
    The truth is if Brian was to buy a FF camera after listening to half the answers here in the belief that his pictures would be "different", he would be sadly disappointed.
    Brian, you might like Leslie's answer, but it is still wrong. If you changed position because you changed sensor size while keeping the same lens, your pictures would be different, but only because you changed position, not because you had a more expensive camera. Shoot from the same spot and you get essentially the same picture, try it with a camera phone and your DSLR. Same spot, different lenses, different sensors but the same picture. In that instance, where there is a very large difference between sensor sizes, there will be a difference in DOF at the same f-stop, but only because of the magnification ratio differences, the subject is reproduced much smaller on the phone.
    The same is true of APS and FF cameras but if you stand in one place and frame the subject the same (use different lenses, or a zoom) the ratio difference is normally small enough to amount to one stop of aperture. That is, two 12"x 18" prints made from: 1, a FF sensor shot at 150mm and f4 at 200iso and: 2, an APS sensor at 100mm and f2.8 at 100iso are identical when shot from the same place.
     
  46. Scott Ferris [​IMG], Nov 26, 2011; 12:16 a.m.
    " In the real world, ..........., and lenses affect perspective and DOF."
    No, in the real world your position and distance to subject and background dictate the perspective, your position, however, might be dictated by lens availability, but that is a side issue. Don't confuse the correct physics and understanding of the thing with emotional irrelevancies.
    (my emphasis)​
    That is all I need to say. As far as I'm concerned, your argument is akin to saying that guns don't kill people: blood loss does. Shooting someone might not technically kill them, but it sort of sets the whole thing in motion.
     
  47. Zack -
    You are completely and totally WRONG!
    Let me break it down for you:
    perspective and DOF are not affected by lens choice because taking the same image from the same distance at the same aperture, and cropping to the desired composition gives you the same DOF and perspective.​
    I never said this. I said that your perspective doesn't change. Your DOF is dictated by focal length, aperture and distance to subject. Your PERSPECTIVE is only dictated by distance to subject and distance to background. Therefore, what I said is that your DOF may change, but your PERSPECTIVE WILL NOT.
    But in the real world, it doesn't work this way. Those of us without near-limitless funds must rely on a variety of focal lengths to get different compositions, and those different focal lengths change the relationship between camera, subject, and background; thus altering perspective and DOF.​
    While lens and camera choice may dictate where you stand, it is only where you stand that dictates perspective. Focal lengths have nothing to do with the relationship between camera, subject and background. If you're standing in the same location with 3 different format cameras and three different focal lengths, the perspective DOES NOT CHANGE! Your DOF may change, but your perspective will not.
    The fact is that unless you can afford to shoot everything with an 8x10 view camera, you can't just, "crop to the desired composition" every time.​
    Again...wrong.
    I do not have an unlimited budget. What I have is a camera and lens selection that gives me the freedom to shoot from 24mm to 200mm (FX) seamlessly. This allows me to choose the perspective I want and zoom accordingly. You see...this is the true power of zoom lenses. They allow the photographer to choose the perspective they wish to create and then frame the shot accordingly using the zoom ring...essentially "cropping to the desired framing"
    While this may seem like it would be expensive, most new photographers buy a kit that gets them from 24-70 (FX) in their DX 18-55mm. They then only need to spend another $200 to get a 55-200mm. While this is not optimal for low light shooting, it gives the photographer all the freedom they need to choose the perspective and zoom to crop.
    If it makes you happy to know that the theoretical physics support your argument, then by all means continue. You are, technically, correct. But if you wonder why so many people are posting photos that "disprove" you or can't understand what you're saying, then go test drive a Kia and a BMW.​
    This is not theoretical physics. It's a LAW of physics. Please keep in mind that I wouldn't be posting about theory...I only post what I have tested and what I have practiced. I am technically correct and I am correct in practice. Also do not assume that I disapprove of people's photos. There are not many photos that I "disapprove of". Every person is creatively free to express what they desire to. If they ask for critique, I will give my opinion...but it is always asked for before it is given.
    BTW, there's a big difference between a Kia and a BMW...just like there's a difference between a D3100 and a D3s. The thing is, a Kia and a BMW both get you from point A to point B. That's their intended purpose, and in no way do they defy the laws of physics to do so. The same goes for a D3100 and a D3s...both achieve the same perspectives from the same physical position in relation o the subject and background and neither defy the laws of physics.
    RS
     
  48. That is all I need to say. As far as I'm concerned, your argument is akin to saying that guns don't kill people: blood loss does. Shooting someone might not technically kill them, but it sort of sets the whole thing in motion.​
    This is useless rhetoric and has no place in this forum... You're very wrong and it's time you come to grips with this.
    I see no reason why your lens availability would dictate your position when, for about than the cost of dinner and a movie for a family of four, you can add a 55-200mm lens to the kit lens on most cameras and achieve unlimited focal lengths from 18-200mm.
    More likely your position dictates your focal length choice...and your position should be chosen by the perspective you wish to convey. The only exception to this is when you physically cannot get to a position to achieve the perspective you desire. Examples would be a photographer being restricted to a press box at a sporting event or the OP being restricted by a wall to his back. These situations mean that the photographer's limitations will dictate the focal length used...but the photographer's position is still what dictates the perspective captured.
    RS
     
  49. If one is on the goal line of LSU and there are 6 foot high players on every 10 yard lines to the Arkansas goal line the farthest one away appears the smallest. The chap at the Arkansas goal line is 100 yards away. The chap at the 50 yard line is of course 50 yards away and appears twice as big. The player at the LSU 10 yard line is 10 yards away and "appears" 10 times as big as the chap at the Arkansas goal that is 100 yards away. One's camera, shoe color, or beliefs do not change this basic geometry of perspective. Maybe some photographers cannot understand "ratios" thus they believe focal length changes perspective? :) Sadly this was once taught in art in grade school.
     
  50. I completely forgot that Nikon has a tool that demonstrated how perspective does not change based on focal length.
    http://imaging.nikon.com/lineup/lens/simulator/
    Notice how when focal length changes, the perspective stays the same.
    Also note that this is not just one image...the water, the shadows, and the woman reading the book change as you zoom in/out.
    This is exactly what was mentioned by using a zoom lens to understand how perspective does not change. You just have to pay attention to realize this.
    If this still doesn't make sense, I will have to demonstrate this weekend when I have the time to go out and make photos.
    RS
     
  51. Leslie -
    The problem is that the OP originally stated that he wants to "compress his background" This would require the OP to move father away from his subject...which he did not have the luxury of doing.
    If he wanted to make his subject stand out from the background and make the background appear father away, then yes, moving closer and using a wider angle would make sense...much like your photo illustrates.
    This is not, however what the OP asked for...if your photo illustrates what he wanted, than it re-iterates exactly why example photos are necessary to give someone the proper solution.
    RS
     
  52. Thanks Richard! Yes there are a couple of problem in this thread. First the OP, Brian, didn't ask about DOF and yet there were many discussion in this thread about this. Second, the OP did said that he could not stay far enough of the subject to get the compression he wanted and wonder if a FF camera would help and of course the answer is NO.
     
  53. Richard: for starters, I didn't actually quote you ... I quoted a line, and then addressed you. I did not mean to make it sound as if I was quoting you directly, and I apologize if I came across that way.
    That said, by guns vs. wounds analogy illustrates my point perfectly, and I will expand upon it. It seems like we're at loggerheads here though, so if you still think I'm crazy I'll just have to accept that.
    1) Guns cause wounds.
    2) Wounds cause blood loss.
    3) Blood loss kills people.
    Thus by the laws of physics, blood loss kills people. By the law of causality, guns kill people. Now to bring it back around:
    1) Different focal lengths alter your magnification.
    2) Altering your magnification means that you need to be at different distances relative to the subject to maintain similar composition.
    3) Changing your distance relative to the subject changes perspective.
    Thus, the law of physics dictates that lens choice does not affect perspective. The law of causality shows that it does affect perspective; perhaps not directly, but it does happen. This is not a knee-jerk reaction to your argument, but a perfectly valid explaination of causality.
    The reason I called your argument 'theoretical physics' is that in order to have a 'pure' comparison of focal length vs. compression, we need to disregard the concept of artistic composition. Since disregarding composition in photography would make the entire art form worthless, we clearly cannot do that. While your argument makes sense in theory, any attempt to prove it while still composing photographs in a practical way is impossible.
     
  54. "Altering your magnification means that you need to be at different distances relative to the subject to maintain similar composition "
    No Zack. This is the way photography works: 1) You pick a composition and 2) shoot a picture. If you don't have the right lens with you, your options are to crop later (instead of a longer lens) or stitch several shots (instead of a wider lens).
    I cannot alter your distance or you would loose you composition. That is why you move around to pick your angle, light incidence and distance for a picture (you don't zoom in and out to compose a picture).
    No offense but your incorrect comments and unrelated analogies just confuse people trying to understand/learn.
     
  55. "in order to have a 'pure' comparison of focal length vs. compression, we need to disregard the concept of artistic composition"
    This just makes no sense, same as the blood or car examples. And they don't contribute to the learning experience of those trying to understand the basics of photography.
     
  56. The OP was clearly asking whether a crop sensor would increase compression when shot from the SAME distance as a full frame camera.
    The answer is of course NO.
     
  57. Mauro Franic [​IMG], Nov 27, 2011; 12:04 p.m.
    The OP was clearly asking whether a crop sensor would increase compression when shot from the SAME distance as a full frame camera.
    The answer is of course NO.​
    Right. Except that shooting from the same distance would yield a different composition. Shooting the same composition would yield ...
    You know what? Nevermind. I give up.
     
  58. Zack,
    Don't give up, go use your camera and learn this stuff, you are 100% wrong. It is easy to emulate this stuff even if you only have one sensor size and one zoom lens.
     
  59. Zack -
    I'm going to use small words and small sentences so you understand:
    Step 1 - Pick your shot. This means you pick the angle, light direction, and distance from subject.
    Step 2 - Compose the shot. If you have a prime lens, you may have to stitch or crop later to get the exact final product. If you have a zoom lens, you can compose in camera to get the proper crop.
    Step 3 - Shoot!
    I will re-iterate the proper use of a zoom lens and the improper use:
    Proper use:
    Once you pre-visualize your photo, find the right location, and set up for your shot, the zoom lens is used to frame the image.
    Improper use:
    Stand in one spot and compose in the viewfinder using the zoom ring.
    RS
     
  60. Richard:
    Normally I wouldn't respond, but your comment was especially offensive, and clearly intended to be so. If your portfolio on this site is indicative of your actual work, I hardly think you've earned the right to speak to a fellow photographer in that way. While the work shown isn't terrible by any means, it's nothing that I wouldn't expect from my Photo 1 students. Please keep your ego in check; at least until you've earned the right to be a jerk. Which, I must say, is a very long way off.
    And no, I'm not saying that I've earned that right - just that you haven't.
    Scott, I guess I just view the process differently. While I never meant to sound like I was arguing the physics of the process, I suppose I have a different idea of lens selection than others. I didn't get my first zoom lens until the late 90s, after shooting for about ten years. These days I shoot mostly with a 500 C/M, and only own an 80mm and a 150mm, which I select based less on a previsualized idea of composition, but more on how far away I would like to be from the subject. For portraits I generally prefer the 150mm, as it lets me get a little further away and it makes us both more comfortable; especially if I'm shooting nudes.
    Perhaps this rationale for lens choice explains why I view compression in the way I do. Or perhaps it's my subject matter. Either way, my explanation works fine based on the photos I take. I do appreciate your (much more polite) attempt to help me though.
     
  61. Zack,
    It is all a learning process, I am still learning after 33 years! Sometimes it just takes one person to put a concept in a different way for an idea or explanation to make sense and click. I didn't have a formal photography education and a lot of the stuff I know is from experience, but that doesn't stop me wanting to learn even more. The best way to learn the physics, techniques and just gain a deep understanding of framing, perspective, lighting and so much more, is actually to do a cinematic course, they take all this stuff for granted in 101 grade courses, movie courses are so much better structured than photographic education courses.
    To return to one of your analogies, "guns don't kill people". Of course they don't, people using guns kills people, just like lenses don't make perspective, people using lenses makes perspective. We tend to use wide angles close to subjects to make them take up a good portion of the frame, and we use longer lenses from further away for the same reason, but it is our position that is changing the perspective, not our choice of lens.
    To continue that analogy, if I was close to a target, I would use a handgun, but that doesn't mean the target wouldn't be just as shot if I used a rifle!
    Take care, Scott.
     
  62. Truer words were never said, Scott. Bringing the firearms analogy back around really puts it into perspective (hah hah!) for me.
    When I read your handgun/rifle statement, my first thought was, "They're not the same at all! The handgun bullet is going to lose momentum not far behind the target, and the rifle bullet will just keep going, and hit whatever is behind it!"
    That was when I realized that I'm not looking at this the same way that you are. You're taking about the shot; I'm talking about all the other stuff that you do in the process that isn't the shot itself.
    Because I have gone so long without zoom lenses (and still never use them on film cameras), and I rarely have more than one or two lenses on my person, I think I've just come to expect that there is a relationship between the gear on your person and how you must compose the photo. While not technically true, it's not technically untrue either. It is a very process-oriented way of looking at things that occassionally overlaps with the science of the thing, but isn't the same.
    Clearly I'm not thinking about hitting a target. I'm thinking about hitting a target and what is behind it at the same time. I'm not selecting a tool for the job, so much as looking for jobs that are done well with the tool in hand.
    Thanks for the analogy Scott. I think I get it now. Hopefully others that share my working methods will understand now too.
     
  63. Zack, I am glad I could help.
    Just as a follow up, for another thread today I took two pictures from the same spot, but used different lenses.
    Background blur is different but subject size and the relationship between the tree and the jumps is consistent.
    Lens were a 200mm and a 17mm.
    00ZhRO-421983584.jpg
     

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