Cropping the exact same as using a telephoto?

Discussion in 'Beginner Questions' started by hello_hello|3, Feb 15, 2016.

  1. Using a telephoto I hear is suppose to provide such effects as "flattening" an image as well as providing a narrower depth of field.

    Do these same properties carry over when I crop an image from a wider lens?
     
  2. Cropping an image gives a narrower field of view, like using a lens of longer focal length. Because a smaller portion of the film or sensor is used, a cropped image cannot be enlarged so much and may show a loss of quality.
     
  3. If you use a wide enough lens [I'm talking extremely wide], there still could be pincushion/barrel distortion, so it's not always true [otherwise it will flatten it, yes]. Keep in mind if you use a telephoto, you will generally get a better image because cropping magnifies the image, making it lose some of the quality it has, while a telephoto uses optical zoom, therefore keeping the quality [optical zoom is almost always preferred to digital zoom in my opinion]
     
  4. Hi "Hello Hello"
    I assume by flattening you mean the perspective of the image or the amount of depth you see on an object. The perspective is controlled by the distance from camera to the subject and not by lens characteristics so assuming the same distance when taking the shot, and cropping to compensate for different focal length, you would see the same amount of flattening/depth or the same perspective.

    That is not necessarily the case with depth of field (DOF) or amount of relative sharpness in front of and behind the plane of focus. The depth of field is reduced when cropping by a linear effect of the amount of the crop while if increasing the focal length, the effect of DOF is reduced by a square effect of the relative change of focal length.

    So if you want to end up with the same DOF with a crop vs longer longer lense approach then here is an example to do that: If you use a lense with a 2X focal length (at a given aperture lets say f/8), then to get the same angle of view, you would need to use a crop factor of 2X yet also to get the same DOF, you would need to take the image with the shorter lens at f/4 instead of f/8.

    The exact math is slightly different yet this will get you very very close to what needs to be done.
    I agree with Mukul that when cropping, you need to make sure you have enough pixels for the size image you want to print or image quality will suffer.
    Hope this is helpful.
     
  5. "Perspective has a Latin root meaning "look through" or "perceive," and all the meanings of perspective have something to do with looking. If you observe the world from a dog's perspective, you see through the dog's eyes. In drawing, perspective gives your drawing the appearance of depth or distance. If we say someone "has perspective," we mean she has a sensible outlook on life. "
    Telephoto lens compressing the distance, "perspective" longer the focal length stronger the distant compression, which is perspective. You cant get the effect by cropping an image let say with a 50mm lens and get an effect of a 500mm lens. When you cropping a part of the image, you just magnifying an existing image drawn by a lens. It is NOT the same as using a tele photo lens. Yes, you can get a birdie in a larger enlargement, but not the advantage of the tele lens. It is big mistake, when people think, a 300mm lens on a cropped camera, 1.5x you going to get a 500mm lens. No, you still have a 300 mm lens, but, a cropped image what the lens supposed to project on a full frame camera sensor or 35mm film.
     
  6. William Michael

    William Michael Moderator Staff Member

    "Telephoto lens compressing the distance, "perspective" longer the focal length stronger the distant compression, which is perspective. You cant get the effect by cropping an image let say with a 50mm lens and get an effect of a 500mm lens."​
    I think that you will find that is incorrect.
    Perspective in a Photograph is determined by Camera to Subject Distance and the Camera's Elevation relative to the Subject.
    If you stand in the one position and take a picture using a Telephoto Lens and then without moving the camera take a picture using a Wider Lens and then crop the image which was taken by the Wider Lens to be the same framing as the Telephoto Lens, then the PERSPECTIVE of the resultant two images will be the same.
    WW
     
  7. William Michael

    William Michael Moderator Staff Member

  8. I'm sorry, William, you totally wrong. Your sample image has no significant distance different from the background and the subject, the car, to see the difference. Try to go out to a long road and take an image with a 24mm lens and a 500mm lens you would see a very big difference how the lens drawing the image, how the road going to merge, the steepness of the angle, the distant with the wider lens shot and with a tele shot.
     
  9. William Michael

    William Michael Moderator Staff Member

    Bela, I know that I am not wrong and I shall not argue about it here. I have taken (Stills Images) and have been DoP (Television) of many a Sporting Coverage at very large Cricket Ovals: in these cases the Cricket Pitch, the Batsman and the Bowler and then the crowd in the distant background are synonymous to the "long road" that you mention.
    It might be wise for you to make the two sample images of a long road and then crop the one made with the wide lens, just as you have described.
    "Hello Hello" could do the same exercise him/herself and s/he will find that indeed, yes, if the camera position is not changed the PERSPECTIVE of the two images will be the same, though as already mentioned, any dramatic cropping will have an affect on the Image Quality.
    WW
     
  10. I read your biography, and very much surprised what you said, and try to demonstrate. Telephoto lenses not for getting the bird in close or the hockey player close only. It has more the that. It has a creative visual effect what many photographer using it. My English is not good enough to argue with you, You my need a real official expert opinion on that.
    00dkTn-560823884.jpg
     
  11. William Michael

    William Michael Moderator Staff Member

    Using a telephoto I hear is suppose to provide . . . a narrower depth of field. Do these same properties carry over when I crop an image from a wider lens?​
    If you stand in the same position and make two images using the same aperture, one with a wide lens and one with a telephoto lens, and then crop the wide image to the same FRAMING as the telephoto image the cropped image will not have the same DoF as the Telephoto image.
    This can be easily seen if you use a DoF application and compare different lenses using the same Subject Distance.
    ***
    If you want to have the same DoF when using two lenses of different Focal Lengths, then you can achieve this by FRAMING each shot the same in the viewfinder. (Which means that you will have to move closer to the Subject when using the wider lens.)
    This is the Axiom of DoF and will hold true for typical Focal Length Lenses (i.e about 20 to 500) and most typical Subject Distances (i.e. Tight Head-shot to Full Length Shot and a somewhat beyond).
    But the Axiom will NOT hold true for: Macro Photography; Extreme Wide Angle Lenses, especially at short Subject Distances; and for Subject Distances which are far away and approaching infinity.
    For any given CAMERA FORMAT provided the APERTURE used and the FRAMING of the shot is the same the DoF will remain the same irrespective of the Focal Length of Lens which is used.
    This Axiom is very powerful knowledge especially for Portrait Photography in any Genre, because it will allow the Photographer to learn by rote the typical/indicative DoF for different Apertures (I use three commonly: F/2.8; F/5.6 and F/11) for the various Framing of Portrait Shots, (e.g. Head Shot; Half Shot and Full Length Shot).
    WW
     
  12. William Michael

    William Michael Moderator Staff Member

    Bela, it is not a matter of having better or worse English skills.
    The one image you posted is very nice, but that one image is not a comparative of two images, one taken with a wide lens and one with a telephoto lens and then the crop of the image taken with the wide lens.
    Truly, I do sincerely suggest that you go do the exercise with two lenses and see for yourself.
    WW
     
  13. To compress the photo of the same near and far objects, you have to step back when shooting with the telephoto lens. That will compress the photo. and make the objects seem closer to each other.
    http://learnmyshot.com/telephoto-lens-perspective-compression-and-the-angle-of-view/
     
  14. I'm sorry, William, you totally wrong.​
    No he isn't, you are!
    Even though Alan already provided a good link (and William provided a nice example too), here's another: http://www.gavtrain.com/?p=4744
    Debunking not only the myth that changing focal length changes perspective but also that you can't zoom with your feet.
     
  15. Alan Klieg demonstrated exactly what I trying to explain for you guys. Even the short video not shoot in the bigger distance scale and wider, versus longer lens effect on the picture, but still shoving the effect I try to explain. I learned enough to know, how lenses focal length changing the image projection and I know what I'm talking about in my 77 years of carrier, had enough time to learn, specially on lenses. The portrait and close shoots and df is an entirely different subject, I don't need to be educated on this matter or any other photography technical subject.
    Dieter, Your explanation is limited for close and model, portrait shot, which I know very well. You better research why landscape photographers using telephoto lenses sometime.
    Go out to a long strait road and shoot with a wide angle lens and shoot with a 300mm lens and try to crop out a same size of image of the wide angle lens and you will find out it will never mach the image drown by a 300 mm lens Thai is the point. On the wide angle lens the road would merge, let say a 90 degree angle and the 300 mm it would be around 10 degree angle. You crop out the wide angle shot and still going to have a 90 degree merging of the road at the distance. It is not the only effect but a most visible effect you can see on the two images done by a two different angle of the lens, and it is not only the angle. Please watch carefully Alan's video. I could easily demonstrate this if I have a time and energy to go out and shot some demo images.
    My answer is still the same. NO. In certain case the distance different not as much and you my see no difference, but in a bigger scale you going to see the difference.
    Please I'm not talking about portrait or nature, bird photography. Those are entirely different subject and technics.
     
  16. Dieter, Your explanation is limited for close and model, portrait shot, which I know very well. You better research why landscape photographers using telephoto lenses sometime.​
    No it is not; the only limitation is that the different focal length images are shot from the same standpoint - here's an example of a landscape shot - and taken from the same standpoint, the 24mm shot cropped matches exactly the 100mm shot uncropped: http://media.digitalcameraworld.com/wp-content/uploads/sites/123/2014/08/Compressed_perspective_cheat_sheet.jpg
    Go out to a long strait road and shoot with a wide angle lens and shoot with a 300mm lens and try to crop out a same size of image of the wide angle lens and you will find out it will never mach the image drown by a 300 mm lens​
    If you take both shots from the same standpoint, then you can crop the tele image out of the wide-angle one - every time for every portion of the image you choose.
    Here's your street shot - taken with a 35 and a 210mm lens without the photographer moving - and again you can crop the 210mm image out of the 35mm and overlay them exactly: http://www.patricktaylor.com/1988#more-1988
    While the images in this demonstration of different focal lengths but taken from the same standpoint look all very different - you can crop the one for a longer focal length out of each one taken with a shorter one - they will overlay perfectly: http://www.nikonusa.com/en/learn-and-explore/article/g3cu6o2o/understanding-focal-length.html
    You have to realize that the video and page Alan Klein linked to above changes both focal length and focus distance at the same time (i.e. the photographer moved the camera backwards to keep the glass of milk the same size in all the shots. That's a scenario that that cannot be replicated by cropping. Because the subject-to-camera distance changed, so did the perspective (i.e. the relation of foreground to background).
     
  17. thank you for all the responses! I'll need to take a moment to process them all!
     
  18. William Michael

    William Michael Moderator Staff Member

    I have taken (Stills Images) and have been DoP (Television) of many a Sporting Coverage at very large Cricket Ovals: in these cases the Cricket Pitch, the Batsman and the Bowler and then the crowd in the distant background are synonymous to the "long road" that you mention.​
    And while I was out making photographs of roads, I made this montage of images which simulates many "Blimp Shots" of a Cricket Oval made at various Focal Length Lenses: 16, 20, 35, 70, 100, 135, 200, 300 and 400
    [​IMG]
    ***
    This second montage is the set of CROPPED images made from the various Focal Lengths images, in the first montage:
    [​IMG]
    WW
     
  19. James G. Dainis

    James G. Dainis Moderator

    William, You have gone to a lot of work to answer the poster's question. That final montage of the same cropped area from different focal length shots is the topping on the cake. I'm sure Mr. Hello appreciates it as do I and other viewers of this forum. Thank you.
     
  20. That was absolutely the most useful example of this I've seen, thanks for that William!
     
  21. Thank you William for your efforts to put together this clear demonstration on an issue that one would think has been resolved a long time ago but that many are having and will continue to have problems with - as evident from this post I discovered when trying to find examples online (which are surprisingly scant):
    When you use lenses of different focal length, or change the focal length on a zoom lens by zooming it back and forth, the field of view and perspective change.​
    FOV, yes; perspective, no, no, no and no! From the same source:
    Changing lenses (and therefore the field, or angle of view) during a photographic session can dramatically affect not only the picture’s angle, and therefore the composition, but also the perspective of the elements of the picture.​
    How the poster arrives at that conclusion when the images that are provided in that post clearly show the opposite to be true remains a mystery. Though I suppose it has a lot to do with being not clear on what "perspective" actually is (and isn't) - if one considers "perspective" and "view", "vista" or "panorama" as synonymous then it is easy to see where the confusion may arise from and why those who apply the geometric definition arrive at different conclusions.
     
  22. It's just another myth to add to 'More megapixels means better pictures' and 'the camera body has more to do with image quality than the lens'
     
  23. William Michael

    William Michael Moderator Staff Member

  24. When you crop you effectively change the sensor/film size into a new format and lenses that were wide before are normals, and normals are portraits. In theory there are some mild optical differences because the lens remains the same focal length, but the frame behaves 100% exactly the same as a longer lens would on the uncropped format. In other words, for purposes of composition, the "crop factor" is real. You don't see the stuff outside the frame, so you will position yourself as if it never existed which will determine the perspective and give you the same composition.
     
  25. Regarding perspective compression, I wrote an article 14 years ago giving a simple mathematical proof that telephoto lenses do not compress perspective. For the physics and math-inclined.
    http://scubageek.com/articles/compression.pdf
    Les
     
  26. William Michael

    William Michael Moderator Staff Member

    Very neat Mathematics. Thanks.
    WW
     

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