scott
Mu-43 Veteran
- Joined
- Nov 15, 2010
- Messages
- 332
Hi, all--
I recently got a Voigtlander 15mm f/4.5 lens and an M39-m4/3 adapter for my G1. I'm planning on scale-focusing it in dim conditions where I need maximum depth of field (with a tripod).
According to the online DOF calculator I used, which accounts for sensor size, the lens should produce images that (for example) are in good focus from about 3.25 feet to infinity when the lens is set at f/8 and focused at 2m.
In trying out the lens, I could tell that this wasn't the case. At that setting, distant subjects looked clearly out of focus to me in pictures at full-screen monitor size, which seems roughly similar to a reasonable-size print.
So after several tests, I decided to check to see if the focus scale was accurate. In the attached picture (a 100% crop of a small printout 2m away) the left image was scale-focused at 2m (with the focus plane measured to be 2m away, of course), and it seems poorly focused. I then made the right image focusing carefully by eye, and it seems better. However, the focus scale showed that the lens was focused at a point about halfway between 2m and infinity. (There are no marks between those numbers.)
Now for the question. If the lens is focusing closer than the scale indicates, and given that infinity focus happens with the lens mechanism closest to the sensor, doesn't this mean that I need to move the lens *back* (probably by somehow shortening the adapter)? I've heard of people shimming lenses *out*, but if I understand this correctly, I have the opposite problem.
And if that's right, does anybody have any suggestions about the best way to do this? Any help would be greatly appreciated.
I recently got a Voigtlander 15mm f/4.5 lens and an M39-m4/3 adapter for my G1. I'm planning on scale-focusing it in dim conditions where I need maximum depth of field (with a tripod).
According to the online DOF calculator I used, which accounts for sensor size, the lens should produce images that (for example) are in good focus from about 3.25 feet to infinity when the lens is set at f/8 and focused at 2m.
In trying out the lens, I could tell that this wasn't the case. At that setting, distant subjects looked clearly out of focus to me in pictures at full-screen monitor size, which seems roughly similar to a reasonable-size print.
So after several tests, I decided to check to see if the focus scale was accurate. In the attached picture (a 100% crop of a small printout 2m away) the left image was scale-focused at 2m (with the focus plane measured to be 2m away, of course), and it seems poorly focused. I then made the right image focusing carefully by eye, and it seems better. However, the focus scale showed that the lens was focused at a point about halfway between 2m and infinity. (There are no marks between those numbers.)
Now for the question. If the lens is focusing closer than the scale indicates, and given that infinity focus happens with the lens mechanism closest to the sensor, doesn't this mean that I need to move the lens *back* (probably by somehow shortening the adapter)? I've heard of people shimming lenses *out*, but if I understand this correctly, I have the opposite problem.
And if that's right, does anybody have any suggestions about the best way to do this? Any help would be greatly appreciated.
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