Diffraction ?

I have read a lot about diffraction at high F stops. So I tried a few close ups at high F stops, as I wanted maximum DOF. I cannot make out any any difference. If any one can, please tell what to look for.

These are 1:1 crops (as there is a current thread on 100% crop, I desist from calling the images so), some 4K pixels long, out of 6K in the frame.


F22


F16


F8

Some more


F8


F16


F22

The above were shot at the closest possible distance (at maximum magnification). The following are full frame, just cropped from left and right.

As I could get maximum DOF and found no degradation, these are shot at F22, and resized to 1000 pixel long.

I am by no means an expert on the specifics behind diffraction, so I will not wade into the waters with regard to the specifics regarding when you should or shouldn't experience it. Suffice it to say that there was heated discussion all over the internet after the D800 was announced, stating that with the pixel size and density of the sensor that users would begin to experience diffraction at f/8 or even larger apertures, and that tripods would be almost mandatory to prohibit movement. Funny how none of that is discussed much post-release.

This is a pretty good article on Diffraction and its effects on digital photography... Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks

What I like most about it is the summary section "Notes on Real-World use in Photography", which essentially states that now you know what it is, here's why you probably don't need to worry about it too much.

For me, personally, I barely think about it. I don't shoot that closed too often, except maybe with macro photography, and then I'm more often than not more concerned about camera or subject movement than I am about diffraction (which as the article states only comes into play when all movement is eliminated). I think this stuff is great to know about, and can help you potentially avoid issues. But I also know that there's some amazing stuff that can be done with digitized light information, and it wouldn't surprise me if there isn't something in the camera firmware that at least partially "heals" some of this given that it knows what aperture you're shooting at. Can't say for sure, but if the numbers behind the D800 optics are right, but experience doesn't bear them out, then there's something going on behind the scenes.

Look at your backgrounds. I see a difference. When shooting macro Changing the aperture does little for the subject in focus because it's so close.

FastGlass said:

Look at your backgrounds. I see a difference. When shooting macro Changing the aperture does little for the subject in focus because it's so close.

Click to expand...

And you should since DOF is changing so the background is more out of focus at f/22 than at f/8.

Where you might see a difference is within the lines on the petal in the last set of photos provided that they were always in focus. At f/8 the transitions might be crisper than at f/22. Reds are tricky anyway, so there's lots that could impact that (nice job capturing them without blowing them out, btw).

So @Marcel, since when do mods do spell check?!

BackdoorHippie said:

So @Marcel, since when do mods do spell check?!

Click to expand...

Usually this is Jack's task, but since I got up before him, I did help him a bit. Plus, we get a bonus for every spelling error we correct. With enough bonus points we get use of the corporate jet.

Marcel said:

Usually this is Jack's task, but since I got up before him, I did help him a bit. Plus, we get a bonus for every spelling error we correct. With enough bonus points we get use of the corporate jet.

Click to expand...

Well if I new jdeg wuz fliing yous guyz areound I wud half laft moor errers fer u two fex.

Diffraction will first present itself as a loss of contrast. This loss of contrast can make an image appear to be less sharp. When I look at the images I definitely see a lowering of contrast as the aperture becomes smaller.

f/16 is always more diffraction than f/4. However, it is always more depth of field than f/4 too. It is a trade off, sometimes (esp macro) the depth of field increase is more valuable than the loss due to diffraction. And sometimes maybe not, if the original depth of field was adequate.

Regarding pixel size, more megapixels is always greater resolution than less megapixels. The pixels do not increase the resolution of the lens/sensor size combination, but more pixels loses less of whatever it was.

LensWork said:

Diffraction will first present itself as a loss of contrast. This loss of contrast can make an image appear to be less sharp. When I look at the images I definitely see a lowering of contrast as the aperture becomes smaller.

Click to expand...

Understood, but bokeh will exhibit itself similarly. Granted, looking at the difference between the f/16 and f/22 shots in the second post there is a significant lightening of the background, but there's nothing stated in the thread that states that these are straight out of camera edits, so it's possible that there was a subtle difference in what was applied in post (i.e. a little more boosting of shadows). Granted, this renders the comparisons a little less useful, so I would hope this isn't the case, but I would have expected to see a bigger difference between F/8 and f/16 if it was.

This is actually one of the better explanations I have found regarding diffraction and how it can degrade or limit resolution.

BackdoorHippie said:

Understood, but bokeh will exhibit itself similarly. Granted, looking at the difference between the f/16 and f/22 shots in the second post there is a significant lightening of the background, but there's nothing stated in the thread that states that these are straight out of camera edits, so it's possible that there was a subtle difference in what was applied in post (i.e. a little more boosting of shadows). Granted, this renders the comparisons a little less useful, so I would hope this isn't the case, but I would have expected to see a bigger difference between F/8 and f/16 if it was.

Click to expand...

Same set of operations were applied to the whole set -
. Picture control : Vivid
. Contrast (under picture control : 2
. Noise reduction : Faster
. Exposure compensation : None
. Active D Lighting : Default

So all the six images are same as far as PP is concerned. For those interested, here is the XML file generated by Capture NX-D for each RAW file. It has all operations performed on the RAW file, and every time the software is opened it applies them.
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