Oversize Filters - Question

speywalker · Jan 19, 2016

Hello I came across some nice contrast filters for my 55mm Pentax 6x7 lens.
Problem is they are 82mm size and the lens is 77mm size.

Is it a good solution if I get reducing rings to downsize the 82mm to 77mm? will this cause vignetting, or any other issues?
Or should I just get the proper filter size?

adelorenzo · Jan 19, 2016

Get a 77-82mm step-up adapter and you are good to go.

Do not buy a reducing (step-down) adapter as this would be for adapting an 82mm lens to 77mm filters, if such a thing exists.

Poisson Du Jour · Jan 19, 2016

speywalker said:
Hello I came across some nice contrast filters for my 55mm Pentax 6x7 lens.
Problem is they are 82mm size and the lens is 77mm size.

Is it a good solution if I get reducing rings to downsize the 82mm to 77mm? will this cause vignetting, or any other issues?
Or should I just get the proper filter size?

82mm filters are BIG and often expensive but are a much better option than stepping rings, which can jam in threads and be quite a tedious thing to try and get off if over-tightened. SMC Pentax 67 lens filters sizes vary greatly from 67mm to 82mm; for photographers using a 35mm kit, filters from that are frequently usefully interchanged to the 6x7 system. For others, it's a case of buy what is needed as you go along.

BTW, you won't really need "contrast filters" for the SMC Pentax 67 55mm; it has legendary excellent contrast. Same with a few others like the SMC Pentax 67 75mm AL.

ic-racer · Jan 19, 2016

Since the viewfinder does not show 100% of the film area, one way to confirm lack of vignetting is to shoot some test images at the smallest aperture and check the corners.

Gerald C Koch · Jan 19, 2016

Hello I came across some nice contrast filters for my 55mm Pentax 6x7 lens.
Problem is they are 82mm size and the lens is 77mm size.

If I read your post correctly what you need are step-up rings. You are stepping up the lens to take a larger filter. In most cases you would only experience vignetting with step-down rings.

shutterfinger · Jan 19, 2016

Looking at this comparison chart http://www.bhphotovideo.com/FrameWork/charts/comp_pentaxmed_3.html your 55mm lens has a 78° angle of view. Measuring from the aperture (correct me if I'm wrong) center a 78° vector and check how far from the end of the lens the outer edge of the filter ring can be before entering into the angle of view. You should be good to go with a step up ring.

bsdunek · Jan 20, 2016

Poisson Du Jour said:
82mm filters are BIG and often expensive but are a much better option than stepping rings, which can jam in threads and be quite a tedious thing to try and get off if over-tightened. SMC Pentax 67 lens filters sizes vary greatly from 67mm to 82mm; for photographers using a 35mm kit, filters from that are frequently usefully interchanged to the 6x7 system. For others, it's a case of buy what is needed as you go along.

BTW, you won't really need "contrast filters" for the SMC Pentax 67 55mm; it has legendary excellent contrast. Same with a few others like the SMC Pentax 67 75mm AL.

Aluminum on aluminum threads do tend to bind. I occasionally run a pencil tip around the threads to lubricate them. There is not enough graphite to get on or hurt anything, and I have no trouble with binding threads.

speywalker · Jan 20, 2016

thanks everyone, shutterfinger love the idea of calculating it all out, and bsdunek the pencil lead lub idea.
Gosh you guys know everything

MattKing · Jan 20, 2016

If you tend to leave the filter on the camera, you will need a new lens cap as well.

wildbill · Jan 20, 2016

All of my round filters are 82mm as well as my lens caps. Every lens I have that isn't 82mm wears a step up ring permanently. I own the 55mm pentax as well.

Dr Croubie · Jan 20, 2016

Get the 82mm filters and a 77-82mm step up ring.
The P67 45mm lens also takes 82mm filters, so if there's any chance that you'll buy this one day, you won't need to get new filters then.

BobMarvin · Jan 20, 2016

If all your filters are 82mm you could simply leave the 77 to 82mm step-up ring in place all the time. It's easy enough to get an 82mm snap-in lens cap. One of these "Hood Hats", which can also cover an attached lens shade, might be even better:

http://www.bhphotovideo.com/c/product/179424-REG/OP_TECH_USA_8001122_Hood_Hat_Medium.html

I use them on my large MF lenses. There are a few different sizes available.

Oversize Filters - Question

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