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What's the easiest and most affordable way for obtaining UV reflectance images?

Started Apr 24, 2021 | Questions thread
ProfHankD
ProfHankD Veteran Member • Posts: 9,147
Re: Shifting the focus plane

Johannes Zander wrote:

I think to correct for removing the filter stack in front of the sensor, you need to bring the sensor nearer to the lens.

from: http://www.ir-photo.net/ir_mod.html

From the formula given on the above mentioned website you would bring the sensor round about 1,3mm forward to the lens. No shimming of the lens needed.

I have a Laowa 10-18mm that takes a flat rear filter. So, I just tested.

With the filter in, focus set to 3 feet is the same as focus to infinity with no glass.

Thus, the rear of the lens does need to be farther away with the filter in. So, I guess I did have it backward? Ooops. That means removing the cover glass can cost you infinity focus... which is very bad. How come I haven't heard everybody complaining about that?

Well, at least the rest of my post above is not wrong... right?

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