Pentax 67: Bayonet-mount filters

Bayonet-mount filters are another useful and interesting accessory for Pentax 67 lenses. While doing mostly black-and-white photography, it is almost impossible to go without special color filters helping to convert colors to black and white in line with your idea, allowing you to control the way they appear in the final image and ensuring that objects are well-separated and clearly defined.

In this article, we will not focus on what bayonet-mount filters to use in certain situations. The sheer number of filters used is quite limited, it is a standard set, and their use largely depends on your personal preferences. I, for instance, mostly use 1A (Skylight), Y2, O2, which are bayonet-type mounts, and sometimes YG, which is a screw mount, with my lenses.

In black-and-white photography you have to alternate filters quite often, sometimes very often — yellow to orange, then orange to yellow, and the other way round. And this triggers a question about their usability.

A majority of Pentax 67 lenses have a bayonet filter option, which allows you to mount both bayonet and threaded filters, as well as to combine them together. That is a really great feature!

Bayonet mount

Let’s look at the bayonet mount closeup. Top image: female mount with two recesses in the thread. It permits another bayonet or screw-in filter. The lenses have the same female mount which also accepts both filter types. Bottom image: male mount with two tabs. It has a very convenient design that allows changing filters quickly and also to stack them together and removing them just as quickly.

Sometimes I use a combination of threaded and bayonet filters. I have a threaded YG which I screw onto the bayonet 1A and as a result get a filter that is almost identical to the bayonet one, as the impact of the 1A filter on black-and-white film can be neglected. What can be easier and more convenient?

Bayonet-mount filters

Some of these data are taken from the Asahi’s original filters manual.

“M” for multi coated filters. “S” for single coated filters

∅	UV	1A	Y2	O2	R2	YG	81A	82A	Lenses
67mm	M S	M S	M S	M S	M S	S	M S	S	90mm F2.8 LS, 90mm F2.8, 105mm F2.4, 135mm F4 Macro, 150mm F2.8, 165mm F2.8, 200mm F4, M* 400mm F4 (rear), M* 800mm F6.7 (rear)
77mm	M S	M S	M S	M S	M S	S	M S	S	55mm F4, 400mm F4 (rear), 600mm F4 (rear), 800mm F4 (rear), 1000mm F8 Reflex (rear)
82mm	M S	M S	M S	M S	M S	S	M S	S	45mm F4, 75mm F4.5, 75mm F4.5 Shift, 300mm F4
95mm	M	M	M	M	M	—	M	—	500mm F5.6
100mm	M S	M S	M S	M S	M S	S	M S	S	55mm F3.5
Exposure factor	1×	1×	2×	3×	6×	2×	1.5×	1.5×	The shutter speed should be multiplyed by this value to get the film properly exposed.
F-stop compensation	0	0	1	1.5	2.5	1	0.5	0.5	The aperture should be opened by this extra f-stop to get the film properly exposed.

All this is also true for color photography, but in general the use of filters there is more infrequent than in black-and-white photography. Of course, I have 80A and 85 filters but use them sporadically, that is why when I required them I just bought ordinary threaded filters.

P.S.

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