Hi all! Hope you can help. I am working on a paint-on-glass project on my multi-plane animation stand, and I can't get my lens to focus perfectly. This is the best I can get:

Obviously I am trying to get the dog in focus. If you zoom in to this picture (also attached) you will see that the edge of the paint is a tiny bit out of focus. I am using a Nikon D5300 with a Nikkor 28mm manual lens. I am using both backlighting and top lighting.

I've tried everything - moving the camera physically closer and farther away from the top pane of glass, trying different combinations of settings and adjusting the lens an infinitesimally small amount between each picture. This is really the most in focus I can get.

What am I missing?

Thank you!

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Most lenses work best in the middle of their aperture settings, so around f8 to f11. This would help establish how much the focus drops off towards the edges. It should be very little for a prime made by Nikon.

I wonder if the closeness of the camera to the flat plane of the glass means that the focus plane is not actually flat, noticeably so in your case? If the focus is sharp at x distance, then this describes an arc at that distance from the lens, and it might be enough of an arc with a shallow depth of field to show up as soft around the edges of the frame. This would confirm your test: moving the artwork further away from the camera improves the situation.

It would also suggest that greater depth of field would help as well.

Thanks Anthony, that was quick! It's good to know the team is responsive. 

If you're looking at the really wide lenses and don't want distortion, you want what are called Rectilinear wide angle lenses. That means the image remains rectangular as much as possible, even out around the edges. It's designed to negate the fisheye distortion tendency. 

Also, any time you find a good lens candidate go online and search up the name of it (brand, focal length, plus f-stop) and look for lenses that have good Sharpness.

Editing now - it let me in. Some lenses are known for having good sharpness all the way out to the edges - obviously those would be the most ideal. I know that machine-vision lenses or security camera/CCTV lenses often are built to maximize sharpness and would be very rectilinear if they're wide angle. I also think a lot of them are very wide if they're to be used for security. But I wouldn't assume a lens is rectilinear or sharp just because it's a CCTV or machine vision lens or made for security cams. I'd still look the particular lens model up and check for those qualities. Maybe even include rectilinear and sharp in your search terms, you may well find an article or comments about it.

2nd edit - Wow Simon, I had never even heard of/thought about that before. Very astute. (I mean the curvature of the focal plane - I did know lenses work best toward the middle of their f-stop range, though I failed to mention it lol - oops! This stuff gets so technical!!)

I just remembered I have a blog post with some details about how I used cropping. I was using a lens that didn't get full coverage for my camera's sensor, the image ended up being a small circle in a black rectangle. But I was able to crop it down pretty far and still end up with an image slightly larger than HD size that looked really good. I was using an extremely wide lens made for CCTV (closed circuit television). Here's that post: Latest Lens Lore

It's not the first lens I talk about, it's the Elbex 8mm f1.4 about halfway down. You can't miss the tiny round image in the big black rectangle. 

Both lenses I mention (until I get onto the zoom at the bottom of the post) are CCTV/machine vision lenses and have excellent sharpness/are rectilinear. If it has TV at the end of the name I believe that means it's a CCTV lens. 

Oh, I just realized, I think most if not all CCTV and security cam lenses use a C-Mount, so would be too small to use on a DSLR. Face-palming hard right now - sorry!! 

Well, the cropping info is still totally relevant. Just don't look for CCTV or machine vision lenses. 

This guy has reviewed a lot of Nikkor lenses -   https://kenrockwell.com/nikon/nikkor.htm

Issues like edge sharpness would be just as important to still photographers, so there is a chance you can get info on that for various lenses.  I mostly use a 28mm for wider shots, but as my sensors on Canon 40d and 7d are not full frame, it doesn't come up as wide as it would on a 35mm still camera or full-frame DSLR.  So sometimes I use a wider Nikkor 24mm.  Mostly though, I choose the 24mm to get a little more depth of field, like where I have a puppet of a smaller scale close to camera as a foreground miniature, trying to look much bigger than other puppets that are really of a similar size.  I don't know if it's edge-to-edge sharpness is better or worse.  These are older lenses made to cover the full 35mm still frame, so with the smaller sensor cropping the outer edges of the lens field off that isn't usually an issue.  

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