Tack sharp focus on subjects eyes....

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chester0711 Regular Member • Posts: 157
Tack sharp focus on subjects eyes....

This is an odd one, as I feel after years of shooting, I should be better. I am struggling to get tack sharp focus on the subjects eyes when I open the aperture nice and wide. Am I expecting the impossible with a 1.8 or 2 aperture?
Some lenses produce better results for then others. For instance with my 50mm (nikon D1.8) I can nail the focus most of the time. With my 85mm (G1.8) I struggle mightly....to the point where I just can seem to hone it in and I get soft eyes....
Anyone have tricks or thoughts on what you are doing to get those eyes into sharp focus?

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 chester0711's gear list:chester0711's gear list
Nikon D700 Nikon D810 Nikon AF-S Nikkor 16-35mm F4G ED VR Nikon AF-S Nikkor 70-200mm f/2.8G ED VR II Nikon AF Nikkor 50mm f/1.8D +4 more
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scokill
scokill Veteran Member • Posts: 6,617
Re: Tack sharp focus on subjects eyes....

chester0711 wrote:

This is an odd one, as I feel after years of shooting, I should be better. I am struggling to get tack sharp focus on the subjects eyes when I open the aperture nice and wide. Am I expecting the impossible with a 1.8 or 2 aperture?
Some lenses produce better results for then others. For instance with my 50mm (nikon D1.8) I can nail the focus most of the time. With my 85mm (G1.8) I struggle mightly....to the point where I just can seem to hone it in and I get soft eyes....
Anyone have tricks or thoughts on what you are doing to get those eyes into sharp focus?

Could be that the 85 1.8 needs some AF fine tune adjustment.  Could be an issue with the lens also.  Have you tested AF on a flat plane at the same distance of your portraits? Are these photos sharp?

 scokill's gear list:scokill's gear list
Nikon D4 Nikon AF-S Nikkor 24-70mm f/2.8G ED Nikon AF-S 70-200mm F2.8E FL ED VR
ronscuba Senior Member • Posts: 1,056
Re: Tack sharp focus on subjects eyes....

chester0711 wrote:

This is an odd one, as I feel after years of shooting, I should be better. I am struggling to get tack sharp focus on the subjects eyes when I open the aperture nice and wide. Am I expecting the impossible with a 1.8 or 2 aperture?
Some lenses produce better results for then others. For instance with my 50mm (nikon D1.8) I can nail the focus most of the time. With my 85mm (G1.8) I struggle mightly....to the point where I just can seem to hone it in and I get soft eyes....
Anyone have tricks or thoughts on what you are doing to get those eyes into sharp focus?

The more you open the aperture, the less area in focus. The longer the lens, the focus area decreases if shot from the same distance.

Here is an online depth of field calculator to see how different f-stops, lenses and distances affect focus area.

https://dofmaster.com/dofjs.html

Only "trick" I know of is the eye-auto-focus feature of modern mirrorless cameras.

KE_DP
KE_DP Veteran Member • Posts: 5,949
Re: Tack sharp focus on subjects eyes....
2

Keep the shutter speed up to reduce any chance of motion - Compare on and off tripod as well.  I find that my studio work is sometimes noticeably sharper than on location - many factors including atmospheric.  Are you using AF or manual?  It's possible you could be experiencing back focus/front focus anomalies.  Testing would be in order to figure that out.  Super shallow DOF can be tricky at times and maybe even shallower than you anticipate.

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Sony a7R IV
rumple
rumple Senior Member • Posts: 1,816
Re: Tack sharp focus on subjects eyes....

chester0711 wrote:

[...]
Anyone have tricks or thoughts on what you are doing to get those eyes into sharp focus?

On top of the other comments, AF Fine Tune will be helpful when wide-open.

I use this system:

"

Save yourself some money and subjective back-and-forth, by doing what I call "live view AF flip tune". It is objective, quick, easy, cheap or free, and can be done in the field:
1) On a tripod, ideally no less than 50 times the focal length (e.g., 50mm --> 2.5metres minimum) square-up on a well-lit target with enough detail to grab focus accurately (e.g., the simple Nikon focus target at https://nps.nikonimaging.com/technical_solutions/d4s_tips/af_fine-tuning/img/img_02.gif, or just a bookshelf or brick wall) and set the lens at its widest aperture.
2) Using centre-point only, flip to live view and focus.
3) Leave live view and focus while watching the focus scale on the lens.
4) If the lens focuses further away than it was with live view, it's back-focusing: add some negative AF Fine Tune. If it focuses closer, then add some positive fine-tune. Goto step 2.

Once the lens stops moving when moved from live view, the AF Fine Tune is correct. Note that, because PDAF focus is not always perfect, the lens may move some of the time - as long as it has stopped moving most of the time, you're good to go.

For zooms, set the AF Fine Tune for near, middle, and far. If the AF Fine Tune number is different at different focal lengths, pick an AF Fine Tune number that is a compromise based on where you expect to use the lens most of the time.

"

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