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I often find it challenging to focus on the eyeball (iris) rather than the eyelashes. The focus points on my Nikon D750 are not dots that I can aim on the iris, but small squares that tend to cover the whole eye and often grab the focus on the eyelashes as they seem to be more contrasty. Are there any techniques to avoid the eyelashes? Do cameras that have an Eye AF features such as the Sony A7r II consistently focus on the iris?

As an example where the eyelash is simply sharper and better in focus,
see this picture (not mine).

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    With a 50mm shooting at f/1.2 from a distance of 1m, you should still have a depth of field of a few centimeters. If you're closer than that, the eye should be plenty large enough that you can focus on just the iris; if you're farther away, the eye should be in sharp focus if the eyelashes are. So is this really a problem? – Caleb Nov 15 '16 at 20:01
  • @Caleb it is not a problem, I know I'm nitpicking. However I do encounter situations quite often where I find that the eyelash is simply sharper and better in focus. See for example this picture (not mine). – vahidg Nov 15 '16 at 20:40
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    Are you shooting in RAW or JPEG? The example you give has more than enough depth of field for the eyes to be completely focused -- notice that not only the eyelashes but also much of the hair is quite sharp. I don't think the eyes are out of focus, they just lack the contrasty lines that hair and eyelashes have, so they don't look sharp. If you're shooting in JPEG, compression may also play a role in that. – Caleb Nov 15 '16 at 20:49
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    Could your example by due to eye-movement? It would take a very shallow DOF to show the eye out-of-focus but not eyelashes. – Itai Nov 16 '16 at 14:02
  • @Caleb I think you have a point and I might have been observing the examples the wrong way. I shoot RAW btw. – vahidg Nov 16 '16 at 22:08
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FWIW the eyeball on that image looks less sharp than the eyelashes are to me. Actual image is here

Possible "solutions:

  • If you are prepared to post-AF manual focus you could use AF and then back focus very slightly

  • or focus on the inner corner of the subjects left eye.

  • or (cheating :-) ) move in by the physical amount needed,

  • or (very cheating) micro-adjust your AF by the desired amount.

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Do cameras that have an Eye AF features such as the Sony A7r II consistently focus on the iris?

I know not but most Sony's (and the A7RII will be included) have "focus peaking" which allows you to either

  • Use AF then check the result with the Af/MF toggle button or

  • Manual focus with utter [tm] precision or

  • Use AF as above then toggle manual/AF toggle (button press by right thumb when focusing) which turns on focus peaking mode and tweak focus if/as desired manually.

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Added: The following is re focus peaking on Sony cameras "which you have not got" (although they did make your sensor). I'm adding it as it is relevant to the general situation that you describe and may be useful to others, even though not necessarily applicable to your current hardware. [I do not know if Nikon implement focus peaking but as the D750 uses a Sony sensor they presumably could].

"Focus peaking" in Sony's implementation adds a colour overlay to areas which are in-focus. [One of white/red/yellow highlighting canm be selected and the degree of highlighting can be varied. I find this feature immensely valuable in selected cases where very precise focusing is required. This may be eg

  • In the presence of multiple alternative closely grouped focus targets - such as a bird in the middle of leaves part way through a tree

  • Where a single very small target is spatially isolated such that it is unlikely to be a preferred auto-focus target - such as a single grass stem physically separated from other objects.

  • On a surface at an angle to the line of view such that there is a physically continuous line on which focus may occur but a specific point is desired.

  • A combination of two or more of the above such as links on a fine chain suspended on space such that AF tends to miss the chain and a specific link is the desired focus point.

Focus peaking's main issue (for me) is that it appears to be contrast based and in some targets highlighting is less positive depending on image content. It can almost always be used once the user is familiar with it.

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    I don't think the focus peaking is a feature of the sensor itself, is it? Isn't it an image processing feature? – mattdm Nov 17 '16 at 11:34
  • @mattdm Yes - it's processing related. My poorly made point is that while there can be unforeseen issues doing various things in various situations, the fact that Sony finds it realistic to implement FP suggests that there are (hopefully no major show stoppers if others wish to do the same wit their sensors. | FP works ~ by high pass filtering the image data and then looking for areas of local contrast difference above some selected level. An electronic viewfinder or display is needed to display the information and the update rate must be adequate to keep up with data changes ... – Russell McMahon Nov 18 '16 at 12:29
  • @mattdm ... in real-enough-time that the user does not find the FP display lagging unnaturally compared to the image proper. The data processing does not seem exceptionally onerous but must be done across the whole image N times/second in enough detail to provide useful focus area delineation. I do not know what sort of processing load that represents. | FWIW I understand that studio video cameras have had FP for 40 or 50 years. – Russell McMahon Nov 18 '16 at 12:33
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Many portraits with eyes that are incredibly sharp have been selectively sharpened in post-processing so that the cornea and pupils are sharpened much more than the surrounding lashes and other facial features. The whites of the eye are also selectively processed to blow them completely out so that no red or yellow is visible.

In the case of the example from Flickr, the whole thing seems to be slightly front focused. Look at the hair on to the right of her face and lying in front of her shoulder. It is even sharper than the eyelashes. On the whole of it, though, the eyes are well enough in focus that one can see some of the red capillaries running across the surface of the whites of the eye.

There is also something else going on here that distracts from her iris and pupils: the catchlights are reflected to the lower left of her pupils with more on the whites of her eye rather than centered on the iris. If she had looked to the lower left or if the reflector had been moved so that the catchlights were centered over her irises the eyes would draw our attention more.

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