Question about shooting full body shots with 50mm

[randy_ramkissoon]

<p>Hi</p>

<p>I've been doing some reviewing of my full body shots (head to toe) photos taken with my Contax Planar 50mm lens on my crop body and have been noticing that to get sharp waist up photos I tend to be shooting at F4 to F5.6.</p>

<p>I'm curious what others peoples experience is shooting with 50mm primes on crop bodies. What F-stop do you normally use to get the same clarity?</p>

<p>Thanks</p>

[shawngibson]

<p>It's a depth of field thing. If you're saying eyes to waist, then you need to stop down.</p>

<p>If you want a lot of out of focus areas but your subject basically in focus, the move your background further back:)</p>

<p>In other words, eyes to tummy in a close shot is a much smaller DoF than a wide open Planar...especially if she is pregnant...oi vay! lol</p>

<p>Head to toe with eyes and tummy in focus is bigger than f/1.4 on a 50/1.4 if you're being critical.</p>

[Matt Laur]

<p>It helps to just run the numbers. If you know your sensor size, your focal length, the distance to your subject, and an given aperture, you can use <strong><a href="http://www.dofmaster.com/dofjs.html">a DoF calculator like this one</a></strong> to see just how much workable range you've got. Then just change a value in the calculation to see how it impacts usable DoF.</p>

[randy_ramkissoon]

<p>Thanks Shawn and Matt.</p>

<p>I feel a bit foolish at the moment (since I do use the dof master website to calculate depth of field. My question originally was more to capture information about what experiences people were having with their particular 50mm lens. This was mainly because I wanted to get an idea on how others would tackle the same type of shot. I now realize I was looking at the situation incorrectly since generally 50mm lens should all act similarly out side of being wide open.</p>

<p>It seems my confusion at the moment has more to do what I would see on full frame vs crop. Would I be correct in assuming if I was going to take the same picture on a crop vs full frame with the same composition I know I would have to stand farther back from the subject with the crop body (because a 50mm lens behaves like a 80mm). As a result should I also assume that I would be required to close down the aperture and therefore to get the same depth of field on a crop I may shoot at F5.6 but on a full frame I should be able to get away with F2.8 because I'm closer to the subject?</p>

[bueh]

<p>It all depends on the light and the situation...</p>

[Matt Laur]

<p>Actually, Randy, if you're closer to the subject, you'll have less depth of field at a given aperture. If you have to stand closer, you'll need to stop down <em>more</em> (say, changing perhaps from f/5.6 to f/8) in order to preserve your working DoF. The calculator will show you that. Just change the values (for sensor size and working distance) and you'll see how those apertures contribute to effectively useful DoF.</p>

[randy_ramkissoon]

<p>Thanks for the feed back. I think I will take the numbers from the dof master and do some more practicing. I'm really bad at judging distances so I will do one better and bring a tape measure.</p>

<p>Thank you again.</p>

[William Michael]

<blockquote>

<p><strong>on my crop body</strong> and have been noticing that to get sharp <strong>waist up photos</strong> I tend to be shooting at F4 to F5.6. . . . I'm curious what others peoples experience is shooting with 50mm primes on crop bodies. What F-stop do you normally use to get the same clarity? . . .</p>

</blockquote>

<p>It doesn’t matter what the FL is. Please understand the Axiom of DoF: it (just about) remains the same for the same framing.<br />For “In the field computations”, for portraiture especially, the <strong>DoF is related to “The Shot” and the Camera’s Format.</strong></p>

<p>For an <strong>Half Shot</strong> – (which you describe “<strong>waist up photos”</strong>) – on an APS-C camera, my safe limit is F/5.6. I can pull F/4 if necessary.</p>

<p>Here is a sample of my DoF cards for 135 format (i.e. Full Frame), which I made years ago and I now know by memory anyway. You get around one more stop of DoF out of an APS-C camera for each shot, so it is easy for me to convert, although I did make up a new set of two cards when I bought my 20D. My limits are on the safe side.</p>

<p><a href="../photo/11721919">http://www.photo.net/photo/11721919</a></p>

<p>I now use these cards as samples for my students – they are easy to make to suit your shooting style and most used apertures (for Flash fill as one example)<br /><br />***</p>

<blockquote>

<p><strong>It seems my confusion at the moment has more to do what I would see on full frame vs crop</strong>. Would I be correct in assuming if I was going to take the same picture on a crop vs full frame with the same composition I know I would have to stand farther back from the subject with the crop body (because a 50mm lens behaves like a 80mm). <em>As a result should I also assume that I would be required to close down the aperture and therefore to get the same depth of field on a crop I may shoot at F5.6 but on a full frame I should be able to get away with F2.8 because I'm closer to the subject?</em></p>

</blockquote>

<p><em></em><br />The statements quoted in italics are incorrect.</p>

<p>a) If you move further back and use the 50mm lens on an APS-C camera to get the same framing (i.e. <strong>the same shot) </strong>as you would have if you used the 50mm lens on a 135 format camera – you will get MORE DoF at the SAME aperture on the APS-C camera (as I mentioned above when describing the Axiom of DoF. You can OPEN UP the aperture of the lens on the APS-C camera about 1 stop (actually about 1?stops) to get the SAME DoF as you would have if you took the same shot (being closer) and using the 50mm lens on a 135 format camera.</p>

<p>Also:<br />b) If you are at the SAME DISTANCE to the subject and use two DIFFERENT Focal Length lenses on two DIFFERENT FORMAT cameras to get the SAME SHOT and also use the SAME APERTURE on each lens – the SMALLER FORMAT camera will provide greater DoF.</p>

<p>See the in-field test, below, which I often do as a class assignment.</p>

<p>***</p>

<blockquote>

<p>I think I will take the numbers from the dof master and do some more practicing. I'm really bad at judging distances so I will do one better and bring a tape measure.</p>

</blockquote>

<p>Generally this is not required – although I do suggest you carry a tape measure in you kit: I do.<br />The point is, if the concept of The Shot and the Axiom of DoF are both understood and the limits of DoF and relevant Apertures for each shot are known: for in the field working portraiture - you don’t ever really need to estimate any distances, for DoF calculations.</p>

<p>WW</p><div></div>

[randy_ramkissoon]

<p>Thanks William. I really appreciate the detail response and examples.</p>