[mattb123]

I had always heard the filter was part of the optical formula too. Having the clear one in there seems to do the trick and I have never bothered with any others.

[ivanvernon]

Because the filters mount at the rear, one would expect that one filter would have to be mounted at all times to keep the focal point where it is expected to be. Lack of a filter could also increase chromatic aberration at the film plane (or focal plane array), if the optics design is based on a filter being there. Is the design such that absence of a filter has only the effect of requiring a change in focus? Is the focus ring distance calibration intended for a filter being present, or not present? Note: back focus would be expected to change by approximately one-third of the filter glass thickness.

Sorry for the error. Here are the three filter inscriptions, in order from top to bottom: clear, pale green, and amber.

[kaseki]

One clear glass filter was installed at the back of the mount when I received the lens. The inscription on this filter reads: "r-1.4x" (where the r appears to be an upside down L and the x appears as a superscript) AND "38x0.5"

Three additional filters are present in the cap of the leather lens storage tube. Their inscriptions may be observed in the attached photo in this order: green, amber, and clear.

I have no further information, and therefore cannot answer the two questions raised in your post.

Trusting that this information is relevant to your concerns. ...

Thanks. I wanted some clarification in case I ever buy that Arsat lens. I think the "r" character is actually a Cyrillic character derived from the Greek letter gamma. I assume it has a "G" sound but am not well enough informed about Russian and/or Ukrainian to make an assertion. The English user guide doesn't list the filters by Cyrillic character identification, or even mention this "fourth filter."

[tuco]

This is great!

Thanks Matt.

[kaseki]

Sorry for the error. Here are the three filter inscriptions, in order from top to bottom: clear, pale green, and amber.

Here is the description from the English user manual:

"The light filter YG-1.4Х, yellow-green and light, improves the tone reproduction of multicolor objects on high-sensitive
photo materials with a slight loss of their sensitivity. With medium-sensitive photo materials, the practically correct tone
reproduction of multicolor objects is attained.
The light filter B-1.4Х, blue, requires a slight enlargement of exposure and is the most suitable for taking pictures with
filament lamps as it provides for the correct tone reproduction of color objects especially in taking pictures with the use of
high-sensitive photo materials.
When shooting outdoors (in the day lighting) the blue light filter singles out a haze, improves the image of shades in a
sunny day, provides for the more correct reproduction of space.
The light filter O-2.8X, orange, fully absorbs Ultraviolet Rays. It is used to obtain a particular contrast in shooting the
compositions with clouds, water surfaces, landscapes with a noticeable shading of verdure, etc."

The O likely denotes orange and the 2.8x denotes the f-stops the filter reduces the light level.

Apologies to all for any appearance of thread-jacking; I really come here to look at the photos.

[tuco]

Something from 2008 that needed a rescan.
Tri-X Pan

[itshimitis]

Sunset in Singapore...

645Z DA 28 - 45 - handheld at 1/8 f/11 31mm ISO 100

[tuco]

Nice picture of an impressive skyline, @itshimitis

Another older shot I'm upgrading to have a digital archive.

400TMY

[BorisKolo]

Sonnar 180/2.8 at 4.8

[volley]

Some really great photographers here, just picked up a 645D and it won't be my last medium format camera.

The portrait is just wonderful!

[Thorrulz]

[desertscape]

Nice B&W series Tuco, as usual. I'm shooting in Taiwan with my 67.

[french]

hello

[Mr. B]

Pentax 6x7, 105/2.4

[susanb]

Nice picture of an impressive skyline, @itshimitis

Another older shot I'm upgrading to have a digital archive.

400TMY

I really like these b&w images. So much texture and interesting elements.

---------- Post added 02-20-18 at 02:41 AM ----------

Nuclear sunset tonight. Just went to the nearby creek.
645D & A 35


645D & FA 45-85

Wow! Gorgeous!