lens coverage, what am i missing?

[steve barry]

I just got my first 8x10 - a sinar norma. I have a nikkor 210 W 5.6 that i use on my 4x5 norma. The image circle is supposed to be 295mm if I am not mistaken, at f/22. Since I do not have a lens for my 8x10 yet, when the norma got here I threw my nikkor 210 on it just to play around. And it covered, so i thought cool. then i played with the rise and fall of the front standard, and to my suprise, it appears that i have over 3 inches of rise/fall before i see the edge of the circle on the ground glass? i didn't even think the lens would cover. what am i missing? it only gets bigger as i stop the lens down to shoot no?

thanks for being patient if this is a retarded question.

[Mark Sawyer]

A few things are going on...

For one thing, some manufacturers are pretty conservative about their coverage claims. And another, you must remember, is that many lenses lose resolution at the outer edge of the image circle, so "illumination" cannot always be caimed as "coverage". (On the other hand, the pictorialists among us might enjoy those less-than-perfect corners, especially those who like the swirly "petzval signature".)

And if you had the camera focused at less than infinity, the coverage naturally increases with bellows extension...

Coverage doesn't so much increase at smaller stops, but fall-off decreases, sometimes dramatically, and those soft corners sharpen up.

[steve barry]

gotcha. i thought "coverage" was strickly a light on film equation. i was focused on infinity though. i guess i will see when i shoot a sheet of film how soft it is.

thanks Mark. i thought coverage did increase at smaller stops, makes sense though what you said.

[Allen in Montreal]

Hi Steve,
I have an older Fuji 210 that covers my 8x10 with abut an inch of movements, (just a guess on my part) at infinity, but it falls off really quickly beyond that.

You were asking about the 150sw, I had a 120sw years ago when I had an 8x10 Arca, it was a great lens, I would imagine the 150sw would be just a great optic too! A 150sw, a Fuji 250 6.7 and a 450/480 would be my dream 8x10 kit.