Center Filter vs. Lens Angle of View for 617 Film/ Image Circle

[Mr_Toad]

Hello, All,

Some years back, I invested in a round center filter with an 82 mm diameter...but didn't really find THAT much need for it with 4x5. (...laziness, i guess).

I just ordered the Shen-Hao 617 Bellows camera, and am expecting the larger 617 film diameter will necessitate the center filter with wider lenses.

QUESTION: Given a center filter with an 82 mm diameter, should I adjust the distance of the filter itself from the lens surface, so that each lens "Angle of View" almost reaches the 82 mm filter diameter, without vignetting? (Center filters are expensive, so I just want to use the one.)

REASON: I purchased various filter step-down rings, to adjust the distance of the center filter from the front glass of my used 4x5 lenses, thinking that the angles of view of a 67 mm, or a 90 mm, or a 120 macro would each be different...and would therefore necessitate different placement of the center filter. (...obviously the 617 film plane will come closer to the Image Circle limits of each lens.)

...Hopefully, I have made myself clear...not having a picture to draw.

Thank you in advance for your help!

Robt.
Dallas

[David A. Goldfarb]

It's generally recommended not to use any filters or step rings between the lens and the center filter, but if you've got the center filter and the rings and the lenses in hand, there's no reason not to test and see what works and what doesn't.

I recently purchased one of the early 47mm/f:8 Super-Angulons as a 6x9 lens, which takes 40.5mm filters. I have a dedicated center filter for my 65mm/f:8 Super-Angulon of slightly later vintage with 49mm rear threads, and I've never seen a center filter with 40.5mm rear threads, so I figured there's no harm in shooting a few sheets of 2x3" film to see if the center filter works with a step-up ring. It reduces the image circle very slightly, but otherwise, it works, and there's still plenty of coverage for 6x9. So I'm glad I tested and learned that in this particular case, I can bend the rules a bit.

In the attached test shot, the top is unfiltered at f:18, 1/8 sec., and the bottom is the 47mm/f:8 Super-Angulon with a B+W Step-Up ring and the 49mm (rear thread) dedicated center filter for the 65mm/f:8 Super-Angulon at f:16, 1/4 sec. The difference is subtle but noticeable. The version with the center filter has more detail everywhere, because the illumination is more uniform.

So you'll need to run your own tests with what you have, because it's not likely that anyone else is using the same combination of center filter, lenses and step rings (even the brand of ring might make a difference, because they're not standard thicknesses) as you have.

[Mr_Toad]

Thank you, David!

I will get my step-up rings all lined up and test it out.

You mentioned it's not recommended to have the filters too far from the lens...but I wonder why. I should search a bit and see if there are some discussions on that topic.

Sigh...work, work, work.....

[David A. Goldfarb]

I think the concern with using the filter too far from the lens is that you could get banding effects. You might test with a scene that has a lot of open sky to see if you get anything of that nature.

Also, center filters usually have a smaller rear thread than the front thread to prevent vignetting with wide lenses, but they're designed to use regular (as opposed to thin-rimmed) filters on the front thread in most cases.

[Nick_3536]

I just ordered the Shen-Hao 617 Bellows camera, and am expecting the larger 617 film diameter will necessitate the center filter with wider lenses.



REASON: I purchased various filter step-down rings, to adjust the distance of the center filter from the front glass of my used 4x5 lenses, thinking that the angles of view of a 67 mm, or a 90 mm, or a 120 macro would each be different...

You might want to do a search for your lenses and 5x7. You don't mention which lenses you're using but you might be worrying too much. If people aren't using centre filters on 5x7 you'll likely be okay.

[Mr_Toad]

Thanks, Nick,

...that's a good thought....will do...