DIY Center ND filter?

[Fermin]

Hello guys and gals!

I have a pretty super angulon 65mm f8 that asides of giving me some trouble when it comes to mounting (recessed linhof lens board system that I am planning to 3d print because there are none in the market of compur 00 size) and placing a shutter release due stupid placement of the shutter lever of the lens, it is also challenging me when it comes to actual shooting. Let me explain myself:

Given that I am not willing to spend +250USD on a center ND filter, I thought about the most stupid solution: what if I create a very high resolution digital image of what the center filter would be, composed of very small dots (more abundant in the center of the image and less abundant the closer to the edges trying to imitate the fading of the original filter, I have some images of it retrieved from internet), print that picture over a transparency with a high quality printer, and then glue it with canada balsam on a UV filter? Would it cause a whole lot of loss of contrast due difraction?

Sorry if the question seems stupid for some of you guys. If the idea is bad please do tell me with some explanation behind, I am very stubborn.

BTW, if you have any idea of how the hell I can trip the shutter without any significant space between the walls of the recessed lens board and the lens itself (the lever is placed perpendicularly to the axis of the lens, very cumbersome), please help me with that too.

Blessings to you all.

[Oslolens]

Test the printed filter!!!!

Both gepe and Kaiser have angles, but they are longer than the 3-1/4" extension. Gepe 603007.

If you still have problems, time to buy a 3D-printed recessed lens board with the extension being more square than round.

Sent fra min SM-S901B via Tapatalk

[Fermin]

Yeah, if I commit to the experiment I will test the filter before using it for anything significant. I just wanted to ask because, well, perhaps someone tried before me and knows that is either a good idea or something very silly and that can save me some time ahahah

[Kiwi7475]

Yeah, if I commit to the experiment I will test the filter before using it for anything significant. I just wanted to ask because, well, perhaps someone tried before me and knows that is either a good idea or something very silly and that can save me some time ahahah

I would expect it will degrade somewhat the IQ but no one can say for sure until it’s tested. I also worry about flairs — again needs to be tested.

Some other ideas I’ve seen mentioned before (including using a candle):

https://www.largeformatphotography.i...-center-filter

https://www.flickr.com/groups/282427...7627245780736/

But I’ve never seen anyone actually posting results on any of these approaches….

[Fermin]

https://www.flickr.com/groups/282427...7627245780736/

But I’ve never seen anyone actually posting results on any of these approaches….

Hmmm... This gave me an actual good idea. I can shoot a neutral white wall at hyperfocal, develop the film and do an interpositive with it. The particles of the silver hallides are roughly of the same size of the visible light wavelenght (perhaps a bit bigger?) so it should not cause too much diffraction and the print will match perfecty the vignetting of the lens. Thank you so much!

[ic-racer]

I inkjet printed a center filter to be used under the light source when printing. With that there is no chance of image quality loss.

[xkaes]

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

[Fermin]

I inkjet printed a center filter to be used under the light source when printing. With that there is no chance of image quality loss.

Thanks for the input! I will medidate a bit more about it but at least I now know that printing is a viable solution.

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.[/URL][/SIZE][/U][/B]

I thought about it too, but seems to me that the vignetting in this lens is quite heavy (it barely covers the film sheet) and I tend to play a lot with zones when exposing so I don't want to sacrifice tonality. I will consider your idea, tho. Thank you!

[Mark J]

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.
If you can somehow make this smoother ( not sure if entirely possible with an inkjet printer ) then you might avoid the effect.

I think ic-racer's suggestion is safer.

However, you might be able to make a film negative of a subject you could make eg. on paper. The object ( say on A2 or A1 paper ) would be the opposite of what you want, so darker around the outside and white in the middle. It may not be easy to paint/draw this smooth, but defocusing slightly will help smooth things out. Then the neg could be tried in front of the lens. I still think that scatter from the silver grains might spoil the overall result, though.

[Tin Can]

pencil on tracing paper

Use Sekonic Spot meter

To check

Simple