Schneider 135 4.7 xenar coverage

[steve barry]

I've been reading around today about the lens on my crown special. I've only ever used it handheld with rangefinder so no movemts. Everything I keep reading says the lens will offer zero movements on 4x5... That it will vignette bad with any movement. Movements on a crown are small, but even maxed out the lens still seems to cover (with light anyhow). Ground glass has nothing vignette and i can see all 4 corners of Gg through lens stopped down. Gg corners are not clipped. Should the lens cover with crown max movements? Thanka

[steve barry]

Thanks for moving...

[Jim Jones]

here is what Schneider says: https://www.schneideroptics.com/info/vintage_lens_data/large_format_lenses/xenar/data/4,7-135mm.html. Note that there is a discrepancy in the math for image data.

[steve barry]

Hi Jim, I saw that, and according to that it should only just cover. I've always thought of image circle in terms of....immediately goes black outside of image circle.

Maybe schneider is just conservative and the crown doesn't have enough movements to slip the coverage off the film. But I read several (10+) posts about how the lens will just cover 4x5 - with zero movements.

[Dan Fromm]

Hi Jim, I saw that, and according to that it should only just cover. I've always thought of image circle in terms of....immediately goes black outside of image circle.

Illumination cuts off sharply for few lenses (except ones with field stops). It usually falls off gradually, as does image quality. For contact printing the circle illuminated (but with how much fall off?) can make sense as a coverage concept, for enlarging the circle with good enough image quality towards the edge is probably better.

[Corran]

The Xenar is basically a Tessar, and the quality of the image falls off pretty fast past nominal coverage. You probably will get an image with the movements you are mentioning, but likely it will have some serious swirl and very little resolution. 135mm is already a little short for a Tessar to cover 4x5 - at wider apertures, the Xenar already performs poorly on 4x5, at least the ones I've used. This result may be acceptable to you depending on your usage. I have used a 300mm Tessar on 8x10 way outside of its spec (2 inches of front fall) and been okay with the results. If you are looking for resolution in the corners, maybe not though.

[Emmanuel BIGLER]

I've always thought of image circle in terms of....immediately goes black outside of image circle.

Coming late to the discussion!
Actually, lens manufacturers' specifications regarding coverage are not always clearly defined; and probably differ from one brand to another.
For Rodenstock Apo Ronars, image coverage as specified by the manufacturer appears to be directly related to published MTF data, i.e. an image diameter beyond which MTF curves drop to a very low level. This because those lenses were used for demanding applications of copying work with the best possible quality. Actually the illumined circle for most dialyte (4/4) designs like the Apo Ronar is bigger than the "official" image circle.

I own an interesting example of a relatively modern lens (designed at end of the 1950s) where the "black circle" starts before any loss of sharpness can be seen, it is the Zeiss Planar 2.8-100 [the model for the Baby 6x9 Linhof Technka, not the Hasselblad's] for which there exist a kind of a "built-in rear lens hood". This device that I have not seen in other view camera lenses is installed behind the lens to cut-off abruptly light rays beyond a nominal image circle considered sufficient to cover the 6x9 cm [2x3"] format with some (small) amount of shift or rise.
Conversely, long focal lengths for medium format cameras, for example the 150 mm or 250 mm Zeiss Sonnar for the 6x6 format, are always mounted with some baffles at the rear, in order to cut-off and absorb stray light generated by slanted rays, so that you cannot experiment with those lenses to see what is their actual full image circle. For sure, a 250 mm Sonnar could probably cover the 4x5" format, at least 6x9, but to use the full image circle, you would have to unmount the lens elements from the barrel ...

See here the abrupt vignetting of the 2.8-100 view camera Zeiss Planar lens when used on the 6x12 format [56x112 mm], with a small, but already off-limits, amount of front rise.
https://www.flickr.com/photos/43175600@N00/28652244681/

When I see this kind of vignetting due to an excess of front rise, I always remember some famous view of Paris by Eugène Atget ;)
https://media.mutualart.com/Images/2009_07/25/0217/594011/70091d38-d74f-4301-b4fe-f911623a853f_g_570.Jpeg

[Pere Casals]

I own an interesting example of a relatively modern lens (designed at end of the 1950s) where the "black circle" starts before any loss of sharpness can be seen, it is the Zeiss Planar 2.8-100 [the model for the Baby 6x9 Linhof Technka, not the Hasselblad's] for which there exist a kind of a "built-in rear lens hood". This device that I have not seen in other view camera lenses is installed behind the lens to cut-off abruptly light rays beyond a nominal image circle considered sufficient to cover the 6x9 cm [2x3"] format with some (small) amount of shift or rise.


Emmanuel, I guess that the rear hud would be good for cameras without movements, as mentioned the circle extension beyond the format only may produce stray light in that situatiojn. For LF the non sharp share of the illumination circle can be useful in certrain conditions, when corners are anyway OOF... allowing to cover a larger format or allowing greater movements, I guess that because of that LF lenses don't have that rear hood, but then we may require a compendium shade to control flare...

Perhaps that Plannar inherited the rear hood from a Hassy version...

[Emmanuel BIGLER]

Emmanuel, I guess that the rear hood would be good for cameras without movements ...
Perhaps that Plannar inherited the rear hood from a Hassy version...

Good point, Pere. Since I purchased this 2.8-100 Planar alone and not with a Baby-Technika, I do not know if my lens was specially fitted for a certain camera, and I have actually no idea if this "rear lens hood" installed on my lens was actually installed all 2.8-100 Planars.
This lens was also part of the standard lens kit for the Linhof Technika Press 23, with helical focusing and no movements. (http://arukucamera.net/LinhofTechnikaPress.html)