Image acuity and focus

arash_hazeghi said:

soft images can happen for many reasons and just seeing the end result will not often suffice to tell what happened

I can spot three major mistakes from your description

1) f/13: stopping down the lens will not make the image sharper, to the contrary it will make it softer due to diffraction effect when using a small pixel camera such as the D500. You only stop down for close range and macro shots when you need DOF. At typical flight distance wide open DOF is more than enough to cover the bird so next time don't use f/13. I almost never ever stop down my big lenses when shooting flight. you cannot get multiple birds in focus by stopping down. if they are not on the same plane only one will be tack sharp.

2) With Nikon cameras the best pattern for BIF is Grp AF which should instantly lock. 3D tracking is not great for BIF although it should work against plain blue sky as there is nothing else for the camera to focus on. With varied BG's 3D AF will be all over the place and screw up the shot

3) your shutter speed is low for BIF. I use 1/3200sec or faster most of the time. It definitely does show some motion blur (look at the catch eye)


This image is incredibly soft and grainy which means the RAW must have been totally soft. there must have been other factors that contributed to get such poor results these include

-Atmospheric refraction effects aka heat shimmers examples here on my blog http://arihazeghiphotography.com/blog/focus-micro-adjustment-is-it-always-needed/ if heat shimmers are present all photos (even static shots) will be soft and is best to pack and just go home. nothing you can do about it

-too much cropping (see these examples : http://www.birdphotographers.net/forums/showthread.php/151192 and http://www.birdphotographers.net/forums/showthread.php/151398)

-least likely : a bad lens. I don't own any third party lenses but I happen to have photographed with the Sigma 500 f/4 lens, it ins't a very sharp lens especially compared to my Nikon 600 FL or 500 PF but it isn't this bad either. however the AF motor in the lens could be bad. After eliminating all the factors above if you are still unable to get good results you might want to send your lens to Sigma factory for evaluation

for a scenario like this D500 should give 90%+ tack sharp files if everything is working as it should. should be a piece of cake


hope this helps

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Brian Sump said:

Ari, I just saw this. I hope I wasn't misleading - I was just posting an image oof for comparison to see if there were ideas as to why it was oof. Shooting with 3D area was a first indication. Second, I didn't realize I was at f13, but understood, I probably should never have been there.

After some posts in this forum and elsewhere, I went out and have been shooting with group and occasional D25. The results have been far more in-focus than previously (see the Avocet and Yellow Headed Blackbird recently posted).

Bummer to hear you thought the Sigma 500mm was less sharp than the Nikkors. Every review I read said the results were hard to differentiate overall from the 500mm f5.6 and f4. Not sure if you made the custom adjustments with the docking station? Those settings make a difference in overall keeper rate I believe, esp handheld.

The other thing I noticed after reviewing images in camera where I could see where the AF focus points were is that I was often missing the eye/head. Part of that is being newer to shooting and the other shooting handheld with a 7.3 lb lens. I have a gimbal and tripod ordered. Also, going to up for a D850 + upgraded battery grip to help improve low-light conditions (per your recent comments in my other thread about high ISO noise on the D500).

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