Question about distance from subject, DoF, sharpness, etc.

I've noticed that when I'm shooting from far distances, I have a much harder time getting my subject's eyes sharp. For example, if I'm standing 20 feet from my subject and I'm at f4 and 50mm, I should have a good 7.5 feet of breathing room to get everything in focus. While I would say my subject is in focus, I don't get nearly the same level of sharpness in the eyes at this distance as I do at say, 5 feet (even at f2.8 or narrower).

My assumption after looking at a couple images objectively is that maybe I'm just not able to meter as accurately at farther distances, so I end up not getting enough light into their eyes to get them really sharp. OR there just aren't enough pixels there to approximate the look of what you get when you're filling more of the frame. The latter would be my guess, but I don't want to shortchange myself if there is something I could do to make things better.

Maybe if someone could post some images at say, 50ish mm from a pretty far distance (15+ feet) that they feel are sharp, it would help me see where I should be and whether what I'm getting is comparable.

(eta... my lenses are f1.4 and f2.8, so my f4 is quite stopped down)

If the eyes are smaller in the frame they won't seem as sharp. Post examples.

That makes sense. I really don't want to post samples because I don't want it to become a discussion about one particular photo of mine. I just want to discuss the theory and not have it become a big mess.

It would be helpful, however, to see samples from people who are only filling maybe 1/4 of the frame at 50mm... and 100% crops of the eyes to show me the best it gets.

Is the reluctance to post images from far distances because no one else knows whether their images are really sharp from that far away, either?

AndreaBFS wrote in post #6007199
That makes sense. I really don't want to post samples because I don't want it to become a discussion about one particular photo of mine. I just want to discuss the theory and not have it become a big mess.

It would be helpful, however, to see samples from people who are only filling maybe 1/4 of the frame at 50mm... and 100% crops of the eyes to show me the best it gets.

I honestly don't think discussing theory will solve your potential problem. It would be best if we could see one of your examples. I promise I will not critique your photo in any other way, although I cannot speak for others.

my images are pretty sharp - maybe they are sharp but it is too small for you? It would be easier to post an example to see if it's really sharp or not. MY 50mm f/1.7 lens is razor sharp when the subject is in focus.

AndreaBFS wrote in post #6007199
That makes sense. I really don't want to post samples because I don't want it to become a discussion about one particular photo of mine. I just want to discuss the theory and not have it become a big mess.

It would be helpful, however, to see samples from people who are only filling maybe 1/4 of the frame at 50mm... and 100% crops of the eyes to show me the best it gets.

AndreaBFS wrote in post #6014338
Is the reluctance to post images from far distances because no one else knows whether their images are really sharp from that far away, either?

I'm not sure if this is what you are talking about but if the person fills most of the frame their eyes are not going to be large enough to see if they are sharp. You can tell by her hair that the shot is sharp. Where the person's head really fills the frame more you can get a lot better eye sharpness.

What you said in your original post I think is probably correct about there not being enough pixel density to really bring out the sharpness in the eyes. Maybe a "eye guru" will give you more insight than I can.

In your first example, the eyes still look pretty sharp to me. That photo is quite a bit closer than what I have in mind, though.

After posting earlier today, I realized I had a better option available than the forum. I spent some time browsing a flickr group dedicated to kids sports and what I found satisfied my curiosity. The bulk of images in the group are no sharper from afar than what I get when I'm at similar distances.

Since we don't know your technique, I will throw a few things your way.
Make sure your shutter speed is fast enough. Even the best of us moves a little, and the longer your focal length, the more apparent this movement will be.
Use the focus point that is closest to the eye. Don't focus and recompose. Think about the difference in distance between your camera and their navel and your camera and their eye. It can be substantial.
Up your f stop a bit. A little extra dof won't hurt you.
Download the DOF caluculator and check out what happens with aperture, focal length and distance.

I wouldn't get carried away with achieving extreme eye sharpness. Excessive eye sharpness (to me) looks kinda spooky & unnatural. Unless, of course, the rest of the photo has extreme sharpness also.

My own take is that because the eyes are bigger, and therefore more prominent in the closer of the two images, they hold the viewers attention to a greater degree, and it is more obvious that they are in focus. Also the catchlights in the eyes of the further image are less obvious, which may give the impression that they are not so sharp.

Just my thoughts.

This may be a bit extreme but if conditions allow:

1. camera on a tripod positioned vertically
2. use one of the off center focal points aimed at the face
3. manual focus to get eyes tack sharp
4. aperture about f8
5 ISO 100
6. timer set at 10 seconds and fire away