First Macro shots, C+C welcome. Thx!

Hey no apology necessary. That is a great shot! Thx for posting

Hey Jim. Thx for the comments

These two shots illustrate the dilemma over what aperture to use for macro shooting (or near-macro in this case).

First f/16. All of the reproductive parts of the flower are within the DOF and they all look reasonably sharp.



But at f/5.6 there is less within the DOF although what there is is visibly sharper.



The loss of sharpness isn't huge (about 20% in resolution measured as lp/ph in the RAW file) and is often well worth it. Past f/16 the rate at which resolution is lost increases but for many shots it can still be worth it. This example is at f/27 and without a comparison shot it doesn't look too bad.



Note that the form of illumination (fill flash or whatever) has absolutely no effect on diffraction. Diffraction is a physical consequence of the wave behaviour of light and depends only on the geometry of the lens in relation to the subject; the most important geometrical factor being the relative size of the aperture.

Other things being equal, using flash might allow you to use a smaller aperture - which increases diffraction as it increases DOF - but for a given aperture a properly exposed shot will show the same amount of diffraction no matter how it is lit.

--
Gerry


First camera 1953, first Pentax 1983, first DSLR 2006
http://www.pbase.com/gerrywinterbourne

Thx for that comparison. That second shot looks great. The first first comparison really helps. I actually like the DOF better at 5.6 (and the sharpness as well). I guess that boils down to taste somewhat as well. Though that shot at 27 doesn't appear to be missing anything!

Gerry: Nearly every shot in my Tiny Wildflower Macros gallery was shot at f-22. Do you think they suffer from diffraction?

I think sometimes at low shutter speeds people confuse camera blurr with diffraction.
--

In the end, the only things that matter are the people we help and the people we hurt. http://pa.photoshelter.com/user/ronkruger

Ron Kruger said:

Gerry: Nearly every shot in my Tiny Wildflower Macros gallery was shot at f-22. Do you think they suffer from diffraction?

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Ron, it depends on what you mean by "suffer". If you mean "do they look any the worse for it?" the answer is no. As I said in my previous post, there is always a choice to be made between the effects of diffraction and shallow DOF. For the type of shot you display the small-aperture/deep-DOF/diffraction-softened approach is the better choice. I usually make the same choice even, as I showed, going beyond f/22 on occasion.

If, however, you mean "do they experience diffraction?" the answer is a resounding yes. It's a law of physics: every lens on every camera ever made or yet to be made loses resolution because of diffraction: this normally starts to show, albeit very slightly, at about f/11 on APS-C cameras and about 1 stop smaller for each step up in format size.

In the strictest terms, diffraction exists at every aperture - it is caused by the effect of the edge of the diaphragm blades on light passing them, so it's inescapable. However, at large apertures the effects of various aberrations are greater than those of diffraction - but these get less as we stop down. The result is that resolution increases from widest aperture as aberrations reduce, reaches a peak when the combined effect of aberrations and diffraction is at its lowest, then declines steadily as diffraction takes its toll at small apertures.

Ron Kruger said:

I think sometimes at low shutter speeds people confuse camera blurr with diffraction.

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Well, that's possible but diffraction shows as an overall softening while camera shake usually shows as a one-directional blur; and it often has two distinct images visible within it - here's an extreme example.



However, diffraction is always there at small apertures whatever the shutter speed. The fact that some people may sometimes get confused about other sources of blur doesn't make diffraction go away.

--
Gerry


First camera 1953, first Pentax 1983, first DSLR 2006
http://www.pbase.com/gerrywinterbourne

Great shots
Ilike all specialy #3,4,5

as mentioned up it seems to be close up not macro but what ever they are I like them.
--
k200d/fuji pro 5/nikond300s
...........
my PPG

http://www.pentaxphotogallery.com/home#section=ARTIST&subSection=7663124&subSubSection=0&language=EN

That makes sense, Gerry, but doesn't the quality and focal length of the lens also affect diffraction? If not, wouldn't the sweet spot be the same for every lens?

One of the first things I do when getting a new lens is some controlled, identical comp, tripod, remote, etc. test shots while running through the f-stops to find the sweet spot. If that varies from lens to lens, which it does, wouldn't the amount of diffraction also differ according to lens?
--

In the end, the only things that matter are the people we help and the people we hurt. http://pa.photoshelter.com/user/ronkruger

Another question, if you don't mind, Gerry:

You said that it doesn't matter how much light, diffraction is the same, but it would seem to me the more intense the light the less diffraction. (The more intense the light the more of it would pass through a small hole.)

And what about quality and type of light. I do know that Pentax camera love flash and seem to process it, especially diffused fill-flash, better than any other light sources.
--

In the end, the only things that matter are the people we help and the people we hurt. http://pa.photoshelter.com/user/ronkruger

Ron Kruger said:

That makes sense, Gerry, but doesn't the quality and focal length of the lens also affect diffraction?

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Not for a particular format, Ron. Diffraction is caused by the "dragging" effect of the aperture rim on the light passing it (a common analogy is the way waves bend at the end of a harbour breakwater, so that the area behind the breakwater does get some wave action even though the advancing waves outside can't get past it).

For every circle there is a fixed ratio between the circumference and the area: 2.pi.r compared to pi.rsquared. The f-stop is the ratio of [diameter of aperture] / [focal length], as you know. What all this means is that everything is in proportion: perimeter of aperture, f-stop and focal length are tied to each other so they scale together and the amount of diffraction simply depends on aperture.

So far, so simple. When we look at the quality of a lens it has no direct effect on diffraction. But if a lens is already blurry the effect of diffraction may be swamped, so although it is numerically the same it may be less obvious visibly .

Ron Kruger said:

If not, wouldn't the sweet spot be the same for every lens?

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Diffraction is only one side of the sweet spot equation. Aberrations are the other side. An absolutely perfect optical design would eliminate all aberrations so the lens would be equally sharp at all apertures, except for the effect of diffraction. In that case the sweet spot would be the widest aperture - because that's where diffraction is least.

However, no lens is perfect and some are less perfect than others. This means that the aperture at which aberrations disappear can vary from lens to lens; as the sweet spot is where the two effects combine with least total effect, it tends to be at a larger aperture for top quality lenses. For example, the FA31/1.8 peaks at f/4 whereas the 18-55 mk1 peaks at f/8. (I'm taking the results from Photozone). However, while the resolution of the 31 is significantly better than the kit lens at f/4, where its superior optical design wins, by f/8 they are very similar - because that's where diffraction has degraded the 31 down to the same level as the kit.

Ron Kruger said:

One of the first things I do when getting a new lens is some controlled, identical comp, tripod, remote, etc. test shots while running through the f-stops to find the sweet spot. If that varies from lens to lens, which it does, wouldn't the amount of diffraction also differ according to lens?

Click to expand...

I hope I've now answered this.

Ron Kruger said:

Another question, if you don't mind, Gerry:

You said that it doesn't matter how much light, diffraction is the same, but it would seem to me the more intense the light the less diffraction. (The more intense the light the more of it would pass through a small hole.)

Click to expand...

Yes, more light passes through the aperture when it's brighter. But some of that extra light hits the edge of the aperture blade. In fact, the proportion of light hitting the edge is exactly the same - see what I wrote above about the geometrical constraints - so the softening effect of diffraction is unchanged. In other words, the image is brighter but neither more nor less soft that a dimmer shot.

Ron Kruger said:

And what about quality and type of light. I do know that Pentax camera love flash and seem to process it, especially diffused fill-flash, better than any other light sources.

Click to expand...

Again, it doesn't make any difference to diffraction. "Soft" light is more uniform on the subject, but every ray of light comes in a straight line from a single spot on the subject through the lens. The aperture is still the same so the edge proportion, and hence diffraction, stay the same.

However, some lighting may encourage flare: I'm sure that a lot of the reputation of Pentax lenses is based on their coatings and internal masking, which reduce flare. Add the problems caused by flare in a poorer lens to diffraction and the overall effect will look worse, but it's the flare and not diffraction that is different.

--
Gerry


First camera 1953, first Pentax 1983, first DSLR 2006
http://www.pbase.com/gerrywinterbourne

@johnbee and zakaria, thanks for the comments. I appreciate it. Guess I should have labeled it first close up shots. Thanks again for looking.

Thanks for that explanation Gerry. I don't think I ever understood diffraction so well.

I'm still absorbing it all, but Gerry sounds like a professor of light, and I appreciate his efforts to explain in detail an aspect I had a working knowledge of, but not a complete understanding.

I approach actual photography in a very practical manner, getting to know my camera and my lenses through experience and then trying to apply it for the effects I want, but this background technical stuff is good to know.

I still don't claim to completely understand it, because some of what Gerry says doesn't seem to jive what what I've put into practice, but that may be my missunderstanding.
--

In the end, the only things that matter are the people we help and the people we hurt. http://pa.photoshelter.com/user/ronkruger

Ron Kruger said:

I'm still absorbing it all, but Gerry sounds like a professor of light, and I appreciate his efforts to explain in detail an aspect I had a working knowledge of, but not a complete understanding.

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Thanks, Ron, but you overstate my expertise. I've spent a lot of my business life between the real professors and other people, giving a "good enough" explanation that gets rid of some misconceptions.

Ron Kruger said:

I approach actual photography in a very practical manner, getting to know my camera and my lenses through experience and then trying to apply it for the effects I want, but this background technical stuff is good to know.

Click to expand...

Me too, actually. But when I read people warning about things such as diffraction I want to understand what the problem is. Like you, I've learned that in practice shooting macros down to f/22 is fine whatever the doom-mongers say.

Ron Kruger said:

I still don't claim to completely understand it, because some of what Gerry says doesn't seem to jive what what I've put into practice, but that may be my missunderstanding.

Click to expand...

I can't claim to understand it fully either, although I think what I've said is the truth. The big practical question is how significant diffraction is compared to other things. It's quite likely that what I've described isn't always obvious in real world shooting.

--
Gerry


First camera 1953, first Pentax 1983, first DSLR 2006
http://www.pbase.com/gerrywinterbourne

Gerry, here's the deal with the practical application of macro and flash as I see it:

I have both the DFA 100mm macro and the DA 35mm macro Limited. With flash, I most often use the 35mm because of the close working distance most don't like.

The sweet spot on my 35 for normal shooting is f-7.1, but in macro, with flash, I can go to f-22 and get clear images.

The flash intensifies and concentrates the light, and with a diffuser, spreads it evenly. Diffraction may be a fairly constant law of physics, but how much diffraction actually effects the outcome of an image, I think, is also dependent upon the intensity and distribution of light on the subject and the quality of the optics that light passes through, plus camera stability, mirror up function and shutter speed.

I believe that the idea of diffraction often takes the blame when the problem really is more due to lighting, quality of the optics and camera stability.
--

In the end, the only things that matter are the people we help and the people we hurt. http://pa.photoshelter.com/user/ronkruger

Ron Kruger said:

Gerry, here's the deal with the practical application of macro and flash as I see it:

Click to expand...

Ron, I don't think we're actually in disagreement here: it's more that we are approaching the same subject fro slightly different directions.

Ron Kruger said:

I have both the DFA 100mm macro and the DA 35mm macro Limited. With flash, I most often use the 35mm because of the close working distance most don't like.

Click to expand...

Fair enough. I often use multiple flash so I can get the lighting I like with any focal length, but that's just a matter of personal taste and convenience.

Ron Kruger said:

The sweet spot on my 35 for normal shooting is f-7.1, but in macro, with flash, I can go to f-22 and get clear images.

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Clear, certainly. So can we all. I'm taking it that by "clear" you mean you can see details throughout most of the image - in other words, a deep DOF - and those details are as sharp as you need for the end use of the shot. If so, I agree 100%.

It just happens that if we open up the aperture some part of the shot will be even sharper, while most of it will be softer. But as that's not what we're aiming for, so what? In other words, while physics is causing diffraction, as long as we're happy with the result physics can stay in the lab.

Ron Kruger said:

The flash intensifies and concentrates the light, and with a diffuser, spreads it evenly. Diffraction may be a fairly constant law of physics, but how much diffraction actually effects the outcome of an image, I think, is also dependent upon the intensity and distribution of light on the subject and the quality of the optics that light passes through, plus camera stability, mirror up function and shutter speed.

Click to expand...

You're saying the same as I've said in my previous posts, in pretty much the same way. Think of having a conversation in a room with music: talk without shouting - if the music is soft the conversation will be audible but in a loud disco it will be lost.

Diffraction is like the conversation here - in some shots its effects will be noticeable (the quiet background) but in others it will be swamped by other factors. But one certain thing is that the diffraction itself will be exactly the same.

Let me use an illustration nearer to home. This tulip was shot in a light tent by natural light only, so not much texture in the petals



As it is so soft, diffraction wouldn't really make much difference (it was at f/11 but f/22 would look pretty much the same). Diffuse flash is the same - there's not a lot of texture there in the first place so diffraction isn't going to be a problem.

For a given lens the optics are the same so that possible variation doesn't exist. I've always taken it for granted that we're discussing " correct" photos - in other words, stability and mirror vibration have never been considerations in what I've written.

Ron Kruger said:

I believe that the idea of diffraction often takes the blame when the problem really is more due to lighting, quality of the optics and camera stability.

Click to expand...

No doubt people do misdiagnose problems. However, my discussion on diffraction has never been about problems. If anything I've tried to dispel the idea of diffraction as a problem by showing pictures where it exists but that are satisfactory. Diffraction is a phenomenon that we can't get away from - all we can do is understand it and take account of it.

--
Gerry


First camera 1953, first Pentax 1983, first DSLR 2006
http://www.pbase.com/gerrywinterbourne