Macro Focus Question

[Kit-V]

Today I was practicing shooting some dead wildflowers against a backdrop of a moving stream. My objective was to keep the wildflowers in crisp focus & allowing the moving water to blur the background creating a fluid negative space. I was using a Canon 400d with a Canon 100mm f/2.8 macro lens. Lens-to-subject distance was about 12" - 18". I was focusing manually with mirror lockup on a tripod.

Even at f/22 I was unable to capture the subject is crisp focus. Was this because the lens-to-subject distance was too short? I would really appreciate some guidance here. Thank you for your help.

[aduke]

I often use that lens on a Canon 40D. There seem to be at least two possible factors, probably more.

First, at f22, there may be enough diffraction to spoil your crisp sharpness. You should test your setup at f8, f11 and f13 and look for diffraction bluring.

Second, the flower itself may have been moving enough to contribute some motion blur.

Alan

[Kit-V]

Thanks, Alan. I suspect that diffraction is not the culprit here since I subsequently shoot at several larger apertures & noted the same blurring. But your reference to blurring caused by slight wind movement might indeed be the culprit. Thanks for reminding me to not overlook the obvious.

[Lost]

You can estimate the DOF here: http://www.dofmaster.com/dofjs.html

This suggests that your usable DOF was less than 1/2 an inch, which might well have been the problem. There is not much you can do about this other than focus stacking (which isn't easy if your subject moves!).

I have a 40D and 100mm macro, and I find diffraction becomes noticeable from ~f16 and up (down?). I try to keep the aperture below this if possible both for sharpness and to help minimise the visible amount of sensor gunk.

[stamper]

I assume that you were trying to fill the frame? Try shooting from further away and this will increase DOF. Assuming that you have plenty of pixels you can then crop. I know that this defeats the purpose of macro and this is why I gave up using my macro lens. The placing of the focus plane is a real art.

[bper]

Here is one thing I do on wildflowers that is a help. The wind blows a lot here in the Spring and if you study it, it will blow (gusty) and then hit a lull for a second or two (or less).

What I do is set up my camera and macro lens on a tripod with a cable release connected. Get everything setup and many times you will need to use manual focus to prevent any delay while the camera refocuses. You can either watch the flower in the viewfinder or sit back with the cable release in your hand and thumb on the button. I don't like my shaky hands to touch the camera. When the breeze hits a lull, click quickly.

This is not a 100% thing as the breeze can move the flower just as you click, but it's the best way I've found to manage the breeze, which can be quite uncooperative.

As a footnote, I have a Nikon D80, which does not have mirror lockup, but rather a mirror delay of .4 seconds. I found this does not work well, because the lull in the breeze often ends during the delay. I also use the M mode to prevent exposure change from any light coming in my viewfinder while I am sitting with my thump on the button. A way around this is use your viewfinder cap if you're using one of the auto modes - Bruce

[Kerry L]

A couple of thoughts about this:

(1) To determine if the problem is subject movement or lens diffraction, zoom in on a flower stem or a petal edge; 200% or more. You should be able to see if the blur is side to side or a halo look. Side to side is movement while the halo look is a lens issue. I'm not familiar with your lens, but with my Nikon 60mm macro, I use a lens hood even though the front element is recessed. Stray light will reduce contrast and could make an image look more unsharp.

(2) Diffraction at f22 will be a problem regardless of the lens. Although with a true macro lens it will less that with a "normal" lens with a macro feature. Find the "sweet spot" aperture for your lens. There are lots of web pages on how to do this, but the general rule is that the 2 mid range fstops are the sharpest. If you stopped down to utilize a slower shutter speed, you can either use a lower ISO setting or use Neutral Density filters. Get the best ND filter that you can afford. You may also want to get several different density factors. 1stop, 2stop, 3stop. To minimize the wallet shock, you can get the biggest filter needed to cover all your lenses and use step down adapters.

I assume that your looking at your images after processing and have sharpened them.

[Dick Roadnight]

A couple of thoughts about this:

(1) To determine if the problem is subject movement or lens diffraction,

Even if you do not have a flash system that will produce a good photo, any flash will tell you if the problem is subject movement... but I have 4 big Metz flashes, and would try them for preference...

Or try a flower at similar range indoors?