Lens coverage

[Thomasbroening]

Do the following lenses cover 8x10? With movements? I mounted them on a new ebony 8x10 and can't tell if they fall off on the corners. Is there somewhere online where I can check it out?


Schneider apo symnar 210mm/5.6
Nikkor SW 90mm 4.5

thanks thomas

[Ron Marshall]

You can find the image circles for modern lenses that cover 8x10 in this chart on the front page of this site:

http://www.largeformatphotography.in.../LF8x10in.html

The 90 has an image circle of 235mm, so it will cover 5x7, 312mm are required to cover 8x10.

The 210 almost will cover, and may cover if stopped down enough, but without any movements.

[Dave Wooten]

A Sironar S 210 will cover with no movements..

[Daniel_Buck]

are the corners of your ground glass clipped? If they are, look through the corners and see if you can see the aperture hole I forget who it was that pointed that out to me, but that seems to be an easy way to tell if the lens covers or not. Stop it to f22 or so, and see if you can see all (or part) of the aperture. If you see all of it, there is no danger of total vignetting. If you see part of it... um... I guess that means that it will be dark in the corners, but not completely black? Someone more knowledgeable than me can correct me on that.

[Anupam]

If you have cut corners on your ground glass you can look to see if the full iris opening is visible. If not, then it indicates the degree of light falloff or even no coverage.

[Dave Wooten]

You might also just want to go ahead and make a photograph at infinity with the lens. Even though coverage might seem adequate on the ground glass, it is possible you will not be satisified with image quality at the edges.

[Jim Noel]

The shape of the iris is the indicator. If it appears as a "Cat's Eye" from any of the 4 corners, that corner will vignette. It may do so wide open, but become essentially round when stopped down and thus not vignette.

[Mark Sawyer]

Bear in mind when checking the corners, you're seeing whether you have illumination, not shrp coverage. Many manufacturers and photographers rate coverage by the area covered with acceptable sharpness, not just hit by light.