DIY Center ND filter?

[Fermin]

I think you will have a lot of problems with this . Assuming what I think you are going to do (your initial suggestion) - make the filter like a half-tone print image, with spots larger near the centre and smaller near the edges - you will get secondary diffraction images at regular intervals ( in angle) around each bright source. Even in mid-tones I think it will mess up the MTF as well.

No, no. I probably did not explain myself clearly. Half-tone would be a very bad idea, as you said. What I meant by "composed of very small dots more abundant in the center of the image and less abundant the closer to the edges" is that all the dots to be as small as the printer can, and to create different densities having those small dots more or less cluttered.

For your second suggestion, an internegative is way easier, but I will have to encounter the same possible problem with the silver scattering the light. It needs testing, of course. Thank you for your thoughts.

@Tin Can: instructions unclear, now I am in Australia about to get married with a kangaroo. But thanks tho.

[Kiwi7475]

There are alternatives to CND filters. One is simply to average-out the light fall-off. Specifically, a wide lens loses light away from the center to the edge. The center will be correctly exposed. Let's suppose your lens has a 1.5f fall-off from center to edge. Just over-expose the film by 0.75f. That way the center will be over-exposed by 0.75f, and the edges will be under-exposed by 0.75f (instead of 1.5f) -- but the rest of the image will be closer to the correct exposure. Overall, the image might meet your needs, especially if you dodge the center of the print.

Here are some other ideas:

http://www.subclub.org/fujinon/center7.htm

While this is true, I find that CND filters are most useful for slides and color neg. Particular for slides, when you only have ~4 stops of dynamic range to keep detail in the highlights and the shadows, trying to fit another 0.75 (almost another stop) on the film may prove impossible.

If it’s just b&w then an inverse vignette filter in Photoshop or, if darkroom printing, moving a circular type mask up and down, can easily correct most of the effect without issues. But when the info isn’t there, one can’t make it up.

I will also say that if one is using 4x5 slides, at about $6-7 per shot + development costs, dealing with a DIY solution and associated tests and issues/artifacts, can quickly add up to the cost of a CND….

[Fermin]

I will also say that if one is using 4x5 slides, at about $6-7 per shot + development costs, dealing with a DIY solution and associated tests and issues/artifacts, can quickly add up to the cost of a CND….

You are right about that, but sadly for me I do not have the money to shoot slides ahahah. I use B&W film, and I know it should be ok, but as I said I do not want to sacrifice tonality. Although the remedy mey be worse than the problem itself!

[Mark J]

No, no. I probably did not explain myself clearly. Half-tone would be a very bad idea, as you said. What I meant by "composed of very small dots more abundant in the center of the image and less abundant the closer to the edges" is that all the dots to be as small as the printer can, and to create different densities having those small dots more or less cluttered

Good that you have been thinking about this. Bear in mind that the printer will still have some periodicity. the spreading of ink may help mask this to a large extent.

[Dan Fromm]

OP, you've rediscovered the center filters made for Bausch & Lomb Metrogon lenses, wide angle lenses for aerial photography.

[Fermin]

OP, you've rediscovered the center filters made for Bausch & Lomb Metrogon lenses, wide angle lenses for aerial photography.

In a personal level, I have the strange tendency to rediscover a lot of things. Among many, I rediscovered the electric motor when I was 13yo. No joke. A bit too late, perhaps. Ahahah

[Drew Wiley]

I suspect that after a lot of fuss and frustration, you'll reconsider buying an actual CF filter. Maybe you'll get lucky finding a used bargain one.

[Tin Can]

I have not shot slides in decades

I made the pencil paper filter for

Large pinhole contact prints under enlarger

Worked fine

[Fermin]

I suspect that after a lot of fuss and frustration, you'll reconsider buying an actual CF filter. Maybe you'll get lucky finding a used bargain one.

Mmmmh... As I said, I am very stubborn. Also, I am very poor ahahah. We will see.

I have not shot slides in decades

I made the pencil paper filter for

Large pinhole contact prints under enlarger

Worked fine

Tin, I am struggling to understand what you mean in this message, and what you meant in the first one. Please consider being more explicit.

[xkaes]

Tin, I am struggling to understand what you mean in this message, and what you meant in the first one. Please consider being more explicit.

Good luck with that!!!