Whats the point of fast lens

<p>Ok, I know there awesome and great for shallow DOF, but here's my problem.</p>

<p>When i shoot more then 1 person, there is always one out of focus. I even try shooting at F4 sometimes and to me they still come out soft. I shoot with both a 50 1.8 and 35 1.8. Usually keep torso and heads within frame (relatively close). Any tips? There's no point in fast lens if i can't make these portraits sharp.</p>

<p>Thanks.</p>

<p>Hi John, a fast lens allows you the option of reducing depth of field, not increasing it.</p>

<p>Since dop for a given focal length, ISO and apeture is a direct function of shutter speed, fast lenses also allow for higher shutter speeds. This can be an advantage in low light or stopping action. But there is no free lunch, you pay for this in dof.</p>

<p>Cheers, JJ</p>

<p>F4 is pretty shallow for group shots, Try F8 or smaller to start. F4 would be okay for a single person in the shot.</p>

<p>Even when you'll be stopping down during the actual exposure (say, f/8 on a group), don't forget that the faster lens is wide open while you're composing. It makes for a brighter viewfinder, and allows your camera's AF system to work better on low-contrast subjects or in dim light before those strobes go off.</p>

<p>Wow really? I usually shoot F2 for single portraits and try to stop a bit further for groups (2+ people)</p>

<p>So then low F numbers are not good for portraits....so then there's no point in fast lens for portraits...(mean this in most cases not all)</p>

<p>Matt that makes sense...there's one point... Thanks</p>

<p>John: spend 10 minutes running various scenarios through this <strong><a href="http://www.dofmaster.com/dofjs.html">online DoF calculater</a></strong> (it's easy, promise). You'll quickly get a sense over how deep a puddle of workable depth of field you've got with your existing lenses used at various apertures and working distacnes from your subjects. <br /><br />Ther's nothing at all wrong with shooting close to wide open on, say, a pair of people. But you've got to get their eyes in a plane that's parallel with your camera's sensor. This can be logistically difficult with groups of people (or can result in some really bland compositions if you're not careful), so the compromise to shooting stopped-down makes plenty of sense for many portraits.<br /><br />On the other hand, you can work with a fast prime at a longer focal length (85, or 105, etc) to get back farther from your subjects, and greatly change the DoF recipe (see that calculator, again, for some thought experiments). <br /><br />I like using my 70-200/2.8 wide open for people, when I can, but using it at 85mm and f/2.8 is a lot different than using an f/1.4 or f/1.8 85mm prime wide open. Remember: it's all about planes and keeping the things you want in focus in that plane.</p>

<p>Thanks Matt for the tool, I will get playing with it for study. I have seen it and know exactly what you mean, just don't understand how people shoot portraits wide open and get so much in focus (unless they are photoshopping it. For example, i'm seen a photo where there was a person totally in focus crisp sharp but everything else was clearly out of focus....just can't understand that.</p>

<p>[[i'm seen a photo where there was a person totally in focus crisp sharp but everything else was clearly out of focus....just can't understand that.]]</p>

<p>If your background is sufficiently far away, then you can easily have everything else out-of-focus.</p>

<p>The DoF calculator will be able to direct you to an appropriate focal length, subject distance, aperture combination.</p>

 

<p>Hi John,</p>

<p>A low number, say f2.8 gives very narrow DOP with a longer lens. We would get a sharp face and out of focus background by shooting the face at this low f number. If we went to f8 and made the same image, the background would now appear much more in focus.</p>

<p>If you have a very fast lens, say an 85mm f1.2, and you shoot at f1.2, the dop for a typical head-shot style portrait is maybe 1 or 2 inches. If the eyes are in focus, the end of the nose won't be.</p>

<p>Why do we want fast lenses?</p>

<p>1) Brighter viewfinder image. A fast lens lets in more light so you can see through the viewfinder more easily.</p>

<p>2) Ability to make images with very narrow DOP. We often use narrow DOP to make our subject stand-off from the background more. See attached flower image. The background grass is very busy so I used f4.0 to make it go blurred or out of focus. This makes the flower stand out more. <br /> <img src="http://www.marulandscapes.ca/gallery pages/land gallery 12.htm" alt="" /></p>

<p>3) To increase shutter speed and stop action. If you shoot at F2.8, the shutter speed for the same shot will be faster than if you shoot at f8.</p>

<p>4) To allow photography in lower light. If we shoot at f2.8, we have much more light than if we shoot at f8. So if it's dark, we may want to let in as much light as we can.</p>

<p>5) Fast lenses tend to be a bit better made than the equivalent slower lenses. The canon 50 F1.2 is much more sturdy than the Canon 50 f1.8.</p>

<p>6) Fast lenses tend to give the out of focus areas in an image a nicer, more appealing look. Not always, but there is a tendency here.</p>

<p>I hope this helps. Cheers, JJ</p>

<p>They are, not there!</p>

<p>You have to run the numbers, John. There's always a sweet spot - positioning your subject, relative to the backdrop, and you, relative to the subject makes the most diference. If you get those things right, you might have a perfect 2-foot-deep area of workable DoF (just enough to get a person looking nicely in focus) while throwing the background well and truly out of focus.</p>

<p>Shooting and seeing in low light.</p>

<p>Even stopped down, fast lenses generally give better color and contrast compared to slower lenses. Plus, if you're shooting wide angle lenses like a 24/1.4, the entire group (two rows of people) is sharp at f/3.5 with the 5DII at the full 21 MP setting. If I tried this with the 24-70/2.8 lens it wouldn't be very sharp at f/3.5 - I'd need to go to about 26mm and stop down to about f/5.6.</p>

<p>Yea i kinda get how DOF works, but then again maybe not exactly how length and f #'s work. I know the closer to the subject you are, the shallower the DOF, and vice versa...i guess what is borthering me is I see photos out there that i try to shoot at the same specs and don't get nearly the same DOF that i seen in other photos....maybe there is something i'm missing though...IDK</p>

<p>Also another thing is buying fast lens and not being able to take advantage of the low F #s because of how shallow it can sometimes be (this depends of course on the type of shot i'm taking). So my guess is, should i shoot farther away from subjects and crop is post to use low F #s and fast shutter speeds?</p>

<p>You are using some very wide lenses for portrait work. That forces you to be very close to the subject to fill the frame and that is why your depth of field is so shallow. If the person moves a little bit they could be leaning into or out of focus. F/5.6 or F/8 is a good place to start if you are hand holding the camera or outdoors using a 50mm lens. A studio setup allows much more control but outdoors you need to be flexible. You can't move the tree or the wall you are trying to use as a prop or backdrop. You have to be creative with your feet. </p>

<p>On a 35mm camera, 105mm is a fantastic length for portraits of people. There is a reason for this: It allows you go get some distance between you and the subject. The longer lens will have less depth of field for a given f/number but the distance between you and the subject will make up for it. But the background will need to be farther away. No free lunch.</p>

<p>Also, be careful about going wider than 50mm for portraits. A wide angle lens can give your subject a fat face or big nose. Don't shoot large people with a wide angle lens if you are trying to flatter them at all.</p>

<p>John does this apply to a DX formatted camera? My 50mm acts as a 75mm in a 35mm format camera.</p>

<p>When I shoot group/party photos with flash, I use manual mode (sometimes aperture priority) and set aperture to at least 6.3 or smaller and set shutter to allow some existing light to expose but a fast enough shutter to prevent blur.</p>

<p>Be aware that the further you are from subjects, the deeper the DOF.</p>

<p>Fast primes used wide open are best for single person portraits since DOF is VERY shallow:</p>

<p>Here's a shot from my <a href="../photo/9304481">Canon 85MM 1.2</a></p>

<p>and another: <a href="../photo/8953976">Canon 85MM 1.2 portrait</a></p>

<p>Check out F stop settings on <a href="http://www.pbase.com/ericsorensen/duckpond2008">group portraits here</a> :</p>

<p> </p>

<p>Just because a fast lens can shoot at a wider aperture doesn't mean you always want to be using it. Some of the best lenses have a max aperture of f/1.4, and when you need f/1.4, you need one of those lenses. Most of the time, however, you can get by just fine with a f/2.8 zoom, because you don't need 1.4 that often.</p>

<p>The truth stands, however, that the most research and the best materials and manufacturing goes into the fast glass. Those f/1.4 lenses are sharper than the f/1.8, f/2, and f/2.8 counterparts. If you stop down to f/2.8 and compare it to a f/2.8 lens, the f/1.4 lens will usually win out in terms of sharpness (resolution, clarity, color, distortion, and everything else, too). Of course there are many exceptions to the rule, but those don't disprove my point.</p>

<p>[i guess what is borthering me is I see photos out there that i try to shoot at the same specs and don't get nearly the same DOF that i seen in other photos....maybe there is something i'm missing though...]</p>

<p>Don't forget to take into account the size of the sensor. The bigger the sensor, the shallower the DOF. Plus, the smaller the sensor, the more the image is cropped, making the lens seem longer.</p>

<p>Good Luck!</p>

 

<p>Hi John,<br />Your DX sensor makes the angle of view on a 50mm lens look like a 75mm, but it's still a 50mm lens. The depth of field is based on the actual focal length of the lens. Your small sensor is only taking a picture out of the center of the lens, but it's not changing the way the lens works. I know this is confusing. Think of it this way: You are taking a picture with a 50mm lens and your camera is cropping the image circle. Nothing else changes. You just aren't using the outer area of the lens but the lens still works the same way it always did on every other regard.</p>

<p>Very fine portraits can be made with a 50mm lens. It just requires a more critical approach because you are standing so close to fill the frame with a head shot that the depth of field will really get short. This can be used to great effect if you know what to expect.</p>

<p>Portraits don't have to be razor sharp, and with all but a very few subjects you don't want a razor sharp portrait. Human beings just don't look good close up. No woman wants to see her pores. A good portrait lens is actually a little soft. A very good trick if you don't have a soft filter is to stretch panty hose over the lens when photographing a woman over 30. (Old school. Now everyone uses $1000 worth of photoshop to mimic two dollars worth of pantyhose.) Soft is good everywhere on earth except Photo.net. Sharpness in a portrait shows off a great photographer (to other photographers) but I doubt you'll sell many portraits to women that way.</p>

<p>A lot of people will tell you to go buy some ridiculously expensive lens to get low light portraits. I say you will be miles ahead to <em>really</em> learn how light works and how best to use it. High end gear will come with time. Until you know exactly where your gear is letting you down you don't need it. In fact, for <strong><em>half</em></strong> the price of a single piece of high end glass you could get a complete used Medium Format rig that will blow away anything you can do with a DX camera anyway. Digital is awesome and the resolution / image quality are there now, but when it comes to tonality there is no replacement for displacement.</p>

<p>My Pentax K20d with 70mm Limited prime lens is a wonder to behold. I love it in every way. But my 30 year old Bronica 6x4.5 with a three dollar roll of film in it is in a whole other class. I don't care what pixel peepers say. Both look awesome on a monitor, but prints don't lie.</p>

<p>This site is a treasure trove when it comes to learning lighting. It's a very fun site, too. :<br>

<a href="http://strobist.blogspot.com/">http://strobist.blogspot.com/</a></p>

<p>John C: just to help you visualize things, here's a shot taken with a 50mm lens:<br /><img src="http://static.photo.net/attachments/bboard/00V/00V6F5-194429684.jpg" alt="" /><br>

I was just a few feet (perhaps six or seven feet, actually) from the subject. This lens was used at f/2 that particular moment, because I wanted to throw the busy background well out of focus, but wanted a touch more DoF than I would have had if I'd used the lens wide open at f/1.4. Using it at f/2 still blurred the background <em>plenty</em>, but it allowed me to get more than just his ear or one eyelash in focus. You'll notice, though, that his shoulders are stlill a bit out of focus - which is <em>fine</em> with me, since this was about his face.<br /><br />Now, if I'd wanted his shoulders and all to be in perfect focus, I could have stopped down further ... but I'd risk pulling the background more into focus. The other option would have been to throw on a longer lens, step back further, and keep is body in focus will still keeping the background well out. But that extra working distance isn't always an option. Or, sometimes it's your <em>only</em> option. You really do have to just <em>do</em> it, in order to internalize a sense of how these things can work for and against you.</p>

<p>A fisheye at f/2.8 depending on the distance will have most every thing is focus. All I am stating is that the focal length also makes a difference.</p>

<p>I may have a similar question to John's.<br>

 <br>

What confuses me about DOF is that when I see portraits taken with a 70-200 f/2.8 at 200mm 2.8 which, I assume, has a<em> really</em> shallow DOF, the background is all nicely blurred out, yes, but the person (in some cases, <em>persons</em>) is all in perfect focus--eyes, nose, body etc.<br>

 <br>

However, when I take pictures using my 50mm f/1.8 wide open which effectively should have a<em> less shallow</em> DOF than a 200mm at 2.8, I easily get some parts of the person's body/face OOF.<br>

 <br>

Is there a certain optimal combination for focal length and aperture that causes this or is it just a matter of good composition and camera positioning?</p>

<p>Matt, just trying to learn more so upon which part of the face did you focus and what focus mode did you use? </p>