I'm thinking of buying a Schneider Xenar 150 mm lens for use on my 6 x 9 Horseman. Has anyone used this lens or its 210 mm version? I do landscape and nature scenics with color chromes. Since its 6 x 9, I don't need a lot of image circle, but I want top quality.

How would this lens compare to a Rodenstock Sironar S 150 mm for use on a 6 x 9 if price is not a concern?

-- Howard Slavitt (has@cpdb.com), November 12, 1998

Answers

My question is perhaps more complicated than just comparing two lenses. As I understand it, when a lens provides much larger image circle than is necessary for a particular format, you are usually losing sharpness and image quality. One person explained to me that it is because there is a lot of extra light that is not hitting the film plan but that is hitting the bellows and thus lowering overall contrast. Is this true? How noticeable would these effects be, for example, with the Sironar S 150 mm used on 2 x 3, vs. 4 x 5 format?

-- Howard Slavitt (nverdesoto@earthlink.net), November 13, 1998.

Howard, In response to your second question, and your concerns about loss of image quality when using lenses with large image circles on smaller formats:

I'm not a lens expert. I don't know if your friend is correct about the potential loss of image quality due to an overly large image circle, internal bellows flare, etc. My own practical experience simply does not support this theory.

Specifically, I've used three lenses (120 Nikkor SW, 305 G-Claron, and 450 Fuji) on both the 4x5 and 8x10 (4x10 with the 120 SW) formats. Additionally, I've used roll film backs with these lenses on the 4x5 format. By your friend's standards, all of these lenses would have extremely large image circles for the 4x5 format, not to mention the roll film formats, and would be expected to produce inferior images on the smaller formats.

I have compared 4x5 and 8x10 B&W negs and color transparencies made with these lenses and could find absolutely no loss of image quality due to the factors cited by your friend. If anything, the overall quality of the negative/transparency image was superior in the smaller format, since the smaller formats only used the central portion of the lens' image circle.

I would think that your 150 Sironar S--from all accounts, an excellent 4x5 lens--would produce equally good images in 6x9, assuming proper focus at the film plane.

Hope this helps, Sergio.

-- Sergio Ortega (s.ortega@worldnet.att.net), November 14, 1998.

I have shared some of your concerns about image quality using roll film with 4X5 lenses. I have been using a Fuji GW690III 6X9 and also use a 6X9 back on my 4x5 Tachihara. I did not want to give up any resolution over the Fuji. I have the 150mm f/5.6 Sironar S and just got a Nikkor 90mm f/8 SW. I am happy to report that the Nikkor has every bit the resolution of the 90mm f/3.5 on the GW690. (This considering the difference in maximum aperture and coverage) The Sironar S is sharper than the Fuji. You have to be very carefull of focus to achieve this though. Keep in mind also these lenses alone cost nearly as much as the GW690 III camera! It is encouraging that this can be achieved over the 4X5 (and 5X7) film area. For the issue of contrast and flare from the excess coverage, use of a lens hood should take care of this. You could likely get as good a lens for 6X9 coverage cheaper, but you will not give anything up getting a good 4X5 lens either.

-- Gary Frost (gfrost@home.com), November 17, 1998.