Lenses for 8x10 and image circle

[Shootar401]

I have a few 5x7 lenses, one of which I know can be used on an 8x10, but in general what is the smallest image circle would I need to cover 8x10? Obviously a small one would not give me any movements which is fine for now.

I'm asking because I have a 210mm lens that has an image circle of 301mm at ƒ/22. It's obviously not enough to cover 8x10 without vignetting, but since I usually shoot wide and crop later, would it really matter that much?

Thanks

[biedron]

The smallest image circle for complete coverage and no movements is the format diagonal - for 8x10 that's 325mm. Perhaps just a tad less since the film holder rails cover a little bit of the film. But if you are willing to shoot wide and crop, then it is really up to you as to what is the smallest IC you need.

Bob

[John Kasaian]

An older lens might soften in the corners rather than vignette---that could be to your advantage depending on what you're after.

[Shootar401]

It's a Rodenstock APO-Sironar-S 210mm which I use with my 5x7 and 4x5

[Leigh]

It's a Rodenstock APO-Sironar-S 210mm which I use with my 5x7 and 4x5

I have that same lens (it's superb).
Its image circle is 316mm per the datasheet. The diagonal of 8x10 film is 325mm, so quite close, within about 1/6" of the corners.

Since the film holder masks the edges of the film, you would likely see very little vignetting, but no movements would be possible.

I don't know where you got the 301mm IC diameter. That value is correct for the Sironar-N, which is a different design.
This may be confusion caused by Sinar. Their Sinaron-S lens is a Rodenstock Sironar-N.

- Leigh

[Shootar401]

My bad, its a Sironar-N. I had my 300mm "s" in my hands when I wrote that.

[Ken Lee]

For general purpose lenses, coverage is stated at infinity distance. As we focus closer, coverage increases. Your lens may not work well for distant landscape scenes, but will have plenty of coverage for other situations.

See http://www.largeformatphotography.info/lenses/LF8x10in.html for a list of lenses suitable for 8x10. It's not complete, but lists many lenses of recent manufacture: filter size, weight, etc.

For 6x7, 6x9, 4x5, 5x7, 11x14 etc. see http://www.largeformatphotography.info/lenses/

For lenses with large coverage, consider the SuperAngulon or a Grandagon.

[Leigh]

Also note that the IC is usually spec'd at two or three stops down from full open, typically f/16. It decreases as you open the lens.

- Leigh

[ic-racer]

I have a few 5x7 lenses, one of which I know can be used on an 8x10, but in general what is the smallest image circle would I need to cover 8x10? Obviously a small one would not give me any movements which is fine for now.

I'm asking because I have a 210mm lens that has an image circle of 301mm at ƒ/22. It's obviously not enough to cover 8x10 without vignetting, but since I usually shoot wide and crop later, would it really matter that much?

Thanks

It depends on how much you crop. I usually overlap the blades of the easel 1/8" to 1/4" over the projected edge of the film, this is a pretty common practice. So, in general, my acceptable image circle for 8x10 is smaller than the diameter frequently posted on these forums. Likewise for you.

For example with a 1/4" overlap of the easel blades on all 4 sides, my Fujinon 125mm (quoted image circle 280mm) makes an image on the film that, when projected, covers the opening in the easel from corner to corner. Of course when you post that your lens with 280mm circle covers 8x10 at infinity, your a posteriori observation is proclaimed 'impossible' and you get flamed off the forum with a diatribe of inappropriate empirical equations and logic....

[Leigh]

Of course, one factor that affects image circle diameter is image quality.

For some lenses, the quality will diminish as you approach the edge of the circle of illumination.
Some manufacturers define the image circle as the area which has uniformly high quality. This is smaller than the coverage area.

- Leigh