7D & Diffraction

[roman_thorn1]

<p>Okay this is probably a question more geared towards all the landscape photographers out there. I'm sure most of you serious landscapers are probably not even using a 7D for your work however I am curious. With diffraction setting well bellow f11 or 16, how does one achieve a greater depth of field without causing this problem. Even if I hyper focus I will still need an aperture of at least f11? </p>

[carnagex_carnagex]

<p>For great depth of field you could always take a few pictures to focus stack. (search on google for Focus Stacking)</p>

[robert lee]

<blockquote>

<p>With diffraction setting well bellow f11 or 16, how does one achieve a greater depth of field without causing this problem.</p>

</blockquote>

 

<ol>

<li>Choose your composition as to not include near field foreground</li>

<li>Use tilt & shift lenses</li>

<li>Bracket focus and stack in post</li>

<li>Shoot stitched pano's with AF enabled, and the individual tiles small enough so that the entire tile is in focus.</li>

</ol>

[scott_ferris]

<p>Roman,</p>

<p>Diffraction is no more, or less, noticeable on the 7D than any other 1.6 crop camera. The fact that the diffuse blur can be more accurately rendered by the 7D than cameras with smaller resolutions is irrelevant. The print quality, from a diffraction point of view, is the same.</p>

<p>This might help. http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm</p>

[g dan mitchell]

<p>You get precisely the same amount of diffraction blur on the 7D that you get on any other 1.6x cropped sensor camera - despite what you are going to hear about the camera becoming "diffraction limited" sooner as you stop down.</p>

<p>To put it as simply as possible: If you make a photograph with a 8MP 1.6x cropped sensor camera and the 7D using the same aperture on the same lens and make the same size prints from both samples you will see exactly the same amount of diffraction blur in both prints.</p>

<p>There is no hard and fast rule about what the "best" aperture is. There are a set of tradeoffs to balance. For example, in one photography you may be concerned with the very sharpest rendition of detail and less with depth of field. In another you may be less concerned with sharpness and need to make a longer exposure. A good way to discover the effect on sharpness at different apertures is to run a series of tests using your gear. This is a quick and effective way to get a real practical understanding of this. (Here is <a href="http://www.gdanmitchell.com/2007/04/12/sharpness-and-aperture-selection-on-full-frame-dslrs">a link to one such test</a> I did with a different camera some time ago.)</p>

<p>A general rule of thumb for cropped sensor bodies if you are concerned about diffraction blur might be to avoid shooting smaller than f/8 unless the need for the smaller aperture outweighs the need for maximum sharpness. This is much less of a concern if you either display online or make relatively smaller prints.</p>

<p>Dan</p>

[craig_meddaugh]

<p>I agree with G Dan Mitchell and Scott Ferris. Go out and experiment with the different apertures. You'll likely find that the diffraction induced softness is hardly objectionable, especially if you need the DOF. </p>

[danielleetaylor]

<p>Diffraction doesn't impact the 7D any more than it would a FF body for a desired DoF at a given FoV.</p>

<p>On a 7D at 17mm, f/8, and hyperfocal, everything from 3.15 feet to infinity is in focus. To achieve the same on a 5D2 requires a 28mm at f/13.5.</p>

<p>The key with either APS-C or 35mm is to use the widest aperture possible for your required DoF and print size. Most photographers lose resolution to diffraction by automatically stopping down to f/16 or smaller when they could get away with something wider. I've finding LiveView to be a tremendous tool for this task as it lets me quickly zoom in and check DoF all around the frame. It lets me find, rather than mentally compute, hyperfocal and optimum aperture. And it reveals much more than a stopped down viewfinder.</p>

<p>Oh yes...the 7D is quite capable of serious, professional, sellable landscape work.</p>

[PuppyDigs]

<p>I often shoot macros at F11 and F16 with a 7D and the additional DOF reveals more detail than the tiny amount of softness introduced. 8x12 and 12x18 prints look great. F8 or F11 are not really "problems." Now F22 and F32 might be if you're making big prints.</p>

[jeff_conrad]

<p>Diffraction on crop-format cameras is an overrated problem (extreme closeups excepted). Diffraction and defocus blur both essentially scale with format, so the tradeoff between the two is the same for 8x10 as it is for APS-C. As Daniel indicated, the key is to scale the aperture (and preferably also the focal length) as well.</p>

<p>Diffraction is a real phenomenon, and it's easy to see if you look for it on a monitor at high magnification. But under normal conditions of enlargement and viewing, it's often imperceptible.</p>

<p>In the plane of focus, there is a tradeoff between aberrations and diffraction; for most small-format lenses, diffraction is the greater problem for apertures smaller than about f/8 or f/11. At the DoF limits, there is a different tradeoff, between defocus and diffraction. The optimal aperture depends on the specifics of a scene: the greater the required DoF, the smaller the optimal aperture for the DoF limits. In most cases where DoF is of interest, the optimal aperture for the DoF limits will be smaller than that for the plane of focus. But if both are imperceptible, it doesn't really matter.</p>

<p>As Daniel mentioned, the best way to avoid diffraction is to use the largest aperture that will give the desired DoF. On a view camera, this can be determined directly by measuring the difference between the near and far image distances. On a manual-focus small-format lens, it can readily be determined using the lens DoF scales. With an AF lens, it's not quite as simple; Canon's DEP mode (the real one, not ADEP) did this quite well, which is why it's unfortunate that it isn't provided on current models. The only practical method then is to visually assess DoF sharpness; it's more of a chore than it should be, but Live View is a big help.</p>

<p>In any event, there's no reason not to use a 7D or any other APS-C camera for landscapes. It's just a slightly smaller format than FF 35 mm, and won't capture quite as much detail. Much as FF 35 mm doesn't capture the same detail as 4x5 ...</p>

[philip_wilson]

<p>My experience agrees with Puppy's you are fine to F11 and generally F16 with the 7D. That said I tend to use the 5DII for landscapes. This link may help you see the diffraction behaviour of APS-C compared to full frame,</p>

<p>http://www.dpreview.com/lensreviews/canon_100_2p8_is_usm_c16/page3.asp.</p>

[bobatkins]

<p>I wouldn't worry too much about stopping the 7D down to f11 or even f16. You'll get some loss of sharpness, but then you'll get <em>some<strong> </strong></em>sharpness loss if you stop a really good lens down past about f5.6. Extended DOF requires some tradeoff.</p>

<p>The 7D has more DOF than a full frame camera with same FOV anyway. It's not just aperture that determins DOF, format size comes in too. True you can stop down more if you shoot a larger format - but you have to to get the same DOF you'd get with a smaller format.</p>

<p>Your best option if you want more DOF is to look at a tilt lens like Canon's T/S series. Then you can tilt the plane of focus to better match your subject. For landscape work this works quite well. The software stiching techniques using multiple shot at different focus settings might work, though they are more often used in macro work than landscape work.</p>

<p>Here are a few articles with more on DOF and diffraction and its realtion to aperture , pixel count and format size</p>

<p><a href="http://www.bobatkins.com/photography/technical/digitaldof.html">http://www.bobatkins.com/photography/technical/digitaldof.html</a><br>

<a href="http://www.bobatkins.com/photography/technical/diffraction.html">http://www.bobatkins.com/photography/technical/diffraction.html</a><br>

<a href="http://www.bobatkins.com/photography/digital/canon_eos_50D_resolution_confusion.html">http://www.bobatkins.com/photography/digital/canon_eos_50D_resolution_confusion.html</a></p>

[ben_goren]

<p>Roman,</p>

 

<p>I urge you to forget everything you think you know about diffraction, depth of field charts,

hyperfocal distances, and the like. Your 7D has made them obsolete.</p>

 

<p>Instead, use Live View with the depth of field preview button engaged. Zoom in, and

you’ll instantly know if you need to stop down more or less, if you need to focus nearer or

farther, or make other adjustments. You can adjust both aperture and (manual) focus with the DoF

button held and instantly see the effect of the adjustments.</p>

 

<p>For bonus points, use a tethered laptop.</p>

 

<p>If, for one picture, you wind up shooting at f/8 focused at 30 feet, and another at f/22 focused a

hair’s breath short of infinity, so be it. That’s what your eyes told you was best for

that particular scene. Perhaps diffraction is affecting the scene at a particular aperture, but it was still better to your eyes to suffer the loss of sharpness of that part of the scene in order to increase the sharpness of another part.</p>

 

<p>Cheers,</p>

 

<p>b&</p>

[roman_thorn1]

<p>Wow thanks everyone, I will check out all those links in the mean time...cheers!</p>

[yakim_peled1]

<p >Tilt is a very good idea. Unfortunately, it's also an expensive one. Your only good option (FL wise) is the 17/4 TS which costs 2.5K.</p>

<p > </p>

<p >Happy shooting,</p>

<p >Yakim.</p>

</p>

[roman_thorn1]

<p>On that note, are there any limitations using the 17mm TS E with an APS C sensor?</p>

[jeff_conrad]

<p>Although Live View is a great feature, especially for T/S lenses, it's interesting that large format and small format have gone in opposite directions here.</p>

<p>The DoF calculator on Sinar LF cameras was a feature adapted from small-format lens DoF scales; it was added to replace stopping the lens down and viewing through a loupe on the groundglass. It wasn't really any better, but it was a lot faster, immediately giving the optimal focus and the required f-number (which depends on having optimal focus).</p>

<p>Small-format cameras with AF lenses have done just the opposite, going from quickly determined settings using the lens DoF scale to visual sharpness assessment. If done carefully, it should work just as well, though the f-number won't be optimal unless the optimal focus has also been found, which requires additional fiddling. The small-format camera has the great advantage of using a larger aperture for the same DoF, so the viewfinder and LCD are much brighter. Prior to Live View, the screen was so small that it was tough to see whether something was really sharp. With the ability to use 10x magnification anywhere in the image area, it's a lot more manageable.</p>

<p>So indeed Live View is a great feature, but it's now the only tool available. It eliminates most of the guesswork, but it's much slower than using DEP, which took only a few seconds.</p>

[jeff_conrad]

<p>The dpreview link that Philip posted is particularly good because the example at the end is one of the few that illustrate both the aberration/diffraction tradeoff in the plane of focus <em>and</em> the defocus/diffraction tradeoff at the DoF limit. The topic actually was covered in great detail years ago by H. Lou Gibson and Lester Lefkowitz, but most recent analyses have seemed to examine only the situation in the plane of focus, which is only one consideration in landscape work.</p>

<p>The tradeoff between DoF and sharpness in plane of focus increases with magnification, so the tradeoff for most landscape work will be much less than that for the dpreview example. For many situations, simply set the aperture for the required DoF, and diffraction won't be an issue.</p>

[yakim_peled1]

<blockquote>

<p>On that note, are there any limitations using the 17mm TS E with an APS C sensor?</p>

</blockquote>

<p>Other than <a href="http://www.fredmiranda.com/forum/topic/825298/3#7846445">financial ones</a>, no.</p>

<p>Happy shooting,<br>

Yakim.</p>

[g dan mitchell]

<blockquote>

<p><em>Diffraction doesn't impact the 7D any more than it would a FF body for a desired DoF at a given FoV.</em></p>

</blockquote>

<p>This is incorrect.</p>

<p>But whatever... In any case, the best way to figure out how diffraction blur affects your photographs and how you'll feel about this is to simply run some tests as I mentioned earlier in this thread.</p>

<p>Dan</p>

[jeff_conrad]

<p>I think Daniel actually has it right. For the “same picture” (i.e., the same DoF with focal length adjusted to give the same AoV in the same size final image) the effect of diffraction is essentially format independent. For a given f-number, the diffraction blur spot is the same for all formats. The smaller format requires greater enlargement, so for a given f-number, the effect of diffraction is more noticeable. But the smaller format can achieve the required DoF at a larger aperture, which results in a smaller diffraction blur spot. So the greater enlargement and greater DoF cancel each other out.</p>

<p>If you run a test to confirm (or refute) this, you need to look at both the plane of focus and the DoF limits, as was done in the dpreview example.</p>

<p>Again, for the same AoV from the same distance using the same <em>f-number</em> , the effect of diffraction is more noticeable in the smaller format. But for the <em>same DoF</em> under the same conditions, the effect of diffraction is the same for both formats.</p>

[arie_vandervelden1]

<p>I'm sitting here looking at a photo shot with my 7D at f/11 in Lightroom. There is indeed some loss of sharpness due to diffraction. There isn't quite the pixel-to-pixel sharpness that I see with smaller fstops.<br /> <br /> However, the diffraction blur can be minimized with a bit of USM sharpening. USM works extremely well for removing this type of blur, as opposed to shake or misfocus which are not easily reduced with USM.</p>