White spot on my shots

marciofs · Oct 4, 2015

I finally found the right place to put the pinhole in my Agfa Box without resulting with vignette.

It would be perfect if it wans't the white spot that came out in the middle of every frame.

I guess it is the reflected light from the pinhole Metallic part, bouncing lighting on the glass in front of it that bounce the light back into the pinhole.

The only way to correct 100% seems to taking the glass of the camera out.

But just in case I am missing something I would like to know about others here opinion about what is causing it and its and correction.

Here an example from a self:

Nodda Duma · Oct 4, 2015

I'd say you're correct.

If you still want glass in front, tilt it enough that the spot no longer lands on the film. Or use a dome (with no optical power). Otherwise remove it.

marciofs · Oct 4, 2015

Nodda Duma said:
I'd say you're correct.

If you still want glass in front, tilt it enough that the spot no longer lands on the film. Or use a dome (with no optical power). Otherwise remove it.

Thanks.

The glass has no optical power at all. It is just a front element protection anyway.

Sirius Glass · Oct 4, 2015

Or remove the glass. Optically it is not needed and it is providing a reflective surface.

Nodda Duma · Oct 4, 2015

Sirius Glass said:
Or remove the glass. Optically it is not needed and it is providing a reflective surface.

Sounds better when you say it

marciofs · Oct 4, 2015

I removed it and did some tests shots today.
But I am sure the problem is solved.

marciofs · Oct 4, 2015

The problem is not solved. The spot still appear in the shots.

Sirius Glass · Oct 4, 2015

Have you cleaned the lens?

DWThomas · Oct 4, 2015

I have to admit I have a problem visualizing what could produce that and yet have the rest of the frame as well covered as it appears. Are you using the camera's shutter to control the exposure? Any possibility the shutter is not closing properly? With some spacing between the shutter and the pinhole plate, the result might be like shooting through a cylindrical hole and projecting the shutter leak via the pinhole. (I am assuming it is a vintage leaf shutter that opens and closes near the center optical axis.)

Maybe try some shots controlling the exposure with a lens cap and the shutter on Time or Bulb as a test?

Interesting!

marciofs · Oct 5, 2015

DWThomas said:
I have to admit I have a problem visualizing what could produce that and yet have the rest of the frame as well covered as it appears. Are you using the camera's shutter to control the exposure? Any possibility the shutter is not closing properly? With some spacing between the shutter and the pinhole plate, the result might be like shooting through a cylindrical hole and projecting the shutter leak via the pinhole. (I am assuming it is a vintage leaf shutter that opens and closes near the center optical axis.)

Maybe try some shots controlling the exposure with a lens cap and the shutter on Time or Bulb as a test?

Interesting!

You are likely to be right.
I will try it.
Thanks.

marciofs · Oct 5, 2015

It works!!!

Sirius Glass said:
Have you cleaned the lens?

The lens was clean.
What I did just to make sure was to remove every glass and leave only the pinhole. And replace the tales that was holding the pinhole for a single tape, in a manner that don't allow any light get throw behind the shutter.

Thanks a million.

White spot on my shots

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