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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?
You need to learn how to adjust what's called Depth of Field.To do that you'll need to fiddle around with the aperture on the lens, it's the other ring, besides the focus ring (and the zoom ring if it has one, which your 28mm won't). You'll find that when you turn the aperture ring, if you look into the lens, the blades inside open or close in a sort of hexagonal pattern. This adjusts how much light gets in, and is referred to as the speed of the lens (how fast the light can get in). That's measured by the lens' f-stop. The lens will have numbers printed on the side so as you turn the aperture ring you can see what f-stop you're at - some lenses will click to the numbers some won't, but you'll be able to stop in between numbers if you want to - they're just a guide.
If you open it wider you let more light in, which makes it faster - this does several things. It's good if you're hand-holding the camera, because you can't hold it rock steady like a tripod does, during a long exposure your hand will tremble or drop a little during the exposure and the picture will come out blurred or smeared. For this reason a lot of people like lenses that are really fast and can open up wide.
But we're using a tripod, so we can go the other way, and in fact that's what you want to do in order to increase the depth of field. As you close down those aperture blades and reduce the amount of light getting in, the depth of field increases. That means the area in focus gets deeper - things both closer to the camera and farther away will come into focus.
Important thing to understand - the f-stops marked on the lens barrel work the opposite way around from how it seems like they would. As the numbers get smaller you're opening up wider and letting in more light, and as they get bigger you're closing it down, letting in less light, and getting a greater depth of field. This is the way you'll want to go.
Here's the procedure you'll need to go through for each shot, they'll be different depending on how bright the scene is. You want to start by setting your aperture so that everything is in focus that needs to be. But that causes changes in the brightness of the image - you test this by snapping a test frame and looking at it - then you adjust the exposure time in the camera to make it either brighter or darker to suit your taste - you might want some shots dark for atmospheric reasons or whatever, and some brighter. After you get these 2 settings properly balanced, now you can fine tune your focus. Shoot a few test frames to make sure everything looks the way you want, and then you can start animating.
You'll need to go through the camera's manual if you're not already familiar with how to adjust the exposure time. But just a little time spent reading and fiddling around with it and you're up and running.
Thanks for your thoughtful message. It's always nice to get a refresher on the technical aspects, but I already know all this (been animating for 10+ years ;)
Like I said in my post, I've already tried different combinations of settings, including every f-stop setting. In the photo attached the dog is aaaaalmost in focus, it's only really by looking at the edge of the paint that you can see the out of focus-ness.
My problem is with the fine tuning of the focus. For some reason I just can't get it focus precisely on the paint, and I've never had this problem before. Hence the mystification!
If you've got any more ideas, I'm all ears!
Oops! Sorry, didn't recognize the name, I assumed you were a newbie. Now I remember seeing you around here before, and you probably could teach me a few things. No sorry, I got nothin' else.
I'm baffled too. In theory you should be able to get a sharp focus on just the dog drawing, since it is flat, with any aperture. (As long as you are not closer than the lens is able to focus - I don't think the 28mm is a macro lens, but mine gets reasonably close, and you have changed the distance already.) Depth of field only comes into it when trying to pull more than one plane into focus.
Could there be dirt on the sensor, or a mark on the back element of the lens? Probably you will have checked already. I got dirt on the sensor of my Canon 40d and the camera service guys improved it but could not completely clean it - it is only clearly visible when stopped down to f-22 or f-32 and aimed at a white card. But it has some effect at medium apertures.
Try putting the dog in a different part of the frame, just to see if there is a fault in just the one spot. If there is, try a different lens to see if it's the lens or the sensor. If not, still try a different lens, even if it isn't the focal length you want, just to see if you can narrow it down.
Can't think of anything else.
Thanks for your reply! I got some ideas from another paint-on-glass animator, and tried a number of other things. I think it is a combination of:
1. the lens focusing more precisely on the center of the field than on the edges
2. the backlighting causing some light spillage onto the edges of the paint, which makes it appear out of focus, or gives it a bit of a halo. This is also more obvious on the edges of the field than in the center.
For #1, I did some tests and the difference between center focus and edge focus is lessened when the artwork is farther away from the camera. Perhaps this would have been obvious to those who are more experts in lenses, but I hadn't quite realized this would be the case. So I have moved the artwork to the lowest level (farther away from the lens), and I'm able to get better focus on things at the side.
Not much I can really do about #2 for this project.
So, there you have it! If anyone else has experience with this, would love to hear about it!
Ah of course - I failed to think of the fact that things toward the edges will be harder to focus/won't look as good in general, but that's absolutely true. One way you could try to deal with it is by shooting wider than you need and then crop in post. Especially since you're using a 28mm lens which is quite wide, that should make a big difference.
I can't edit my posts in here anymore - maybe I need to use a different web browser. When I click the edit button it just jumps back to the top of the page, to Tess' first post on this thread.
What I wanted to add is you could try pulling your camera back, if your setup will allow that. If it won't then I suppose your only options would be to use a wider lens (I don't think they make them much wider than 28 without getting into serious fisheye type distortion) or to make the images you place on the glass smaller. And that way you would doubtless lose some resolution and detail and sharpness etc. Plus the difficulty of how to reduce the size in the 1st place, I suppose by scanning the artwork and making smaller copies.
A thought - a DSLR will take a much bigger image than you need for HD video, and many bigger than 4k as well. What resolution will you finish the film in? So you could move the animation in from the outside edge, and plan to crop the images in post so it would then be closer to the new edge. That would make more use of the centre of the lens. The drawback is that you would work with a smaller video image in Live View, so small precise moves or changes are more difficult.
Strider, I just tested it and I can't edit my post either, same thing happens. I'm using an iMac with Safari 12.0.3.
Wanted to edit because I see now that my suggestion is the same as yours, I just hadn't read carefully enough.
Obvious point, perhaps, but a focusing card would show when it is sharp, and might be helpful to show where the edge sharpness drops off.
Edit function is fixed. Reported it to Support and they fixed it fast.
Yes, I used a focusing card to determine that the effect (less focus on the edges) is lessened when the artwork is farther from the lens. And I also adjusted the artwork to match the new level/placement in the field.
Feels a bit like a band-aid, I guess I will have to look into getting an additional lens! But I'm not so much of a lens expert, and as Strider mentioned above, 28mm is already pretty wide. Anyone know if there's a specific type of lens I should look for, to minimize this effect?