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10-14-2010, 08:57 AM   #1
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DOF practice
Lens: 80-200mm M w/ext. Camera: K-X Photo Location: Pa ISO: 1600 Shutter Speed: 1/30s Aperture: F22 

Two handheld attempts here that I'm wondering what could be done, other then my own additional practice, to get a crisper image.
At the angles they are captured at, I believe the DOF is deep enough; however, I'm not certain if there is a point of too much f-stop that creates a loss of IQ.



I know the compositions aren't stellar and the lighting,, but I want to get this DOF ironed out before I start working on the additional aspects.

10-14-2010, 09:39 AM   #2
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unless you have very steady hands... 1/30 at 80mm may produce shake... and if you shot closer to 200mm... that is likely where the lose of detail is coming from... 80% of great macro shots are on some sort of track/tri-pod
10-14-2010, 10:36 AM   #3
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Also, even though the k-x is pretty good with high ISO, you really want to be shooting with it much lower because noise levels will remove some of the details. For planned handheld macro work, you'll probably want to use the flash so you can get at least 1/180" (onboard flash). Try also to diffuse it a little with something (piece of scotch tape, wax paper, etc). It looks (from the shadows) like you may have been using a flash of some sort though, so I don't really understand the 1/30".
10-14-2010, 03:52 PM   #4
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Macro IQ at high f-stop

QuoteOriginally posted by Zig Quote
..... however, I'm not certain if there is a point of too much f-stop that creates a loss of IQ.....
Yes, there is IQ loss at high f-stop, and it is exacerbated when shooting macros.

A more accurate equation for the Airy disk diameter (diffraction spot diameter) than usually given is:

D= 1.22*f-stop*(1+m)*wavelength (for greenish light, D_microns~(2/3)f-stop(1+m) )

So in your photos, the effective f-stop with respect to diffraction was actually greater than f22.

Guessing the mag was about 1/2, and using the wavelength of greenish light, the diffraction spot diameter is about 22 micrometers. This is 4 times larger than the distance between K-x pixels, 5.5 micrometers, so it is likely that resolution was lost.

It might be worth your time to take a series of photos at different f-stops to find out when resolution begins to degrade for your camera and lens.


Last edited by newarts; 10-14-2010 at 05:32 PM.
10-14-2010, 04:24 PM   #5
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I am not seeing any photos at all just 1) and 2) literally.

Scratch that.... I am now ????
10-15-2010, 10:25 AM   #6
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newarts - thanks for clarifying that equation. I was returning today to ask a few questions about the undefined so I could apply it.

Thanks to everyone for the replies - every little bit helps, as I've realized very quickly this macro thing isn't a frame and shutter happenstance.

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