Best to go less wide

[swmcl]

Hi all,

I want to pose a hyper lens-threadical. My first lens is a 300mm wide angle lens with a image circle of 420mm. The second 300mm lens has a 340mm image circle. The last and third 300mm lens has a 240mm image circle. Assuming all lenses will only ever be used at f16 or less (ie. f16, f22, f32 etc), which lens is most likely to be sharp?

An alternative way of thinking about it is - Is it technologically easier to produce a high resolution image with a less wide angled lens?

The reason I ask is because the choices are so extreme. I feel as if the focussed image of a wide angle is not going to perform as well as a tightly focussed image at the same focal length. I bet I should buy lenses that exceed my image size by only just enough to allow some movement. Only buy 5x7 lenses at most for a 4x5 system - dont buy 8x10 lenses and use them on a 4x5 camera.

How am I going?!

Cheers,

[Dan Fromm]

Why don't you ask the lenses?

And surely there are other considerations that matter, e.g., maximum aperture, weight, ...

[Ernest Purdum]

All lens design is compromise. It's easier to make a sharp lens with a lesser coverage circle, but it is also easier to make it lighter, smaller and/or less expensive. The designer has to choose and we have to figure out what we want. Your choosing smaller coverage would be good for a lot of landscape or portrait workers, but an architectural or product specialist would want to be able to use his movements more freely.

Another question is whether or not we would ever notice the sharpness difference.

[Nick_3536]

Are any of those coverage numbers real? Or are some limited by stops?

Not to mention if you're at small stops you'll be hard pressed by that alone.

Other issues then resolutions.

[Ron Marshall]

If you don't need the extra IC for movements then go for the lighter lens.

[Eric Woodbury]

Also, larger ICs allow more light within the camera. Unless it is very black in there or you use a very good lens shade, that extra light bounces around and onto the film reducing contrast.

[cotdt]

what i notice about wide angles is that, stopped down for focusing, the image circle is really small and hard to see the whole picture on the ground glass.

[Mark Sawyer]

Are any of those coverage numbers real? Or are some limited by stops?


They're fairly realistic; the Fujinon W, Nikkor W, and Caltar S and SII are all listed by their manufacturers as having 420mm of coverage, the Rodenstock Geronar at 340mm, and the Apo Sironar and Apo Ronar at 264mm. (Yeah, I peeked at a chart...)

Figures are usually for being at f/22 at infinity focus, but many process lenses are listed for coverage at 1:1, which is very different...

Any modern (coated) lens should be very sharp, but there are differences in performance. Among my own lenses, I've noticed as much difference between lenses of the same design and manufacturer as between lenses of different designs by different manufacturers. But it still isn't that much differnce. I'd say any good coated tessar or, if you really want lots of movements, a good plasmat. Either will cover 8x10, so neither will be really "tight" on coverage.

The small, lightweight lenses will probably be process lenses (usually dialytes) which will need to be closed down a little for optimum performance (you indicated you'd be doing this anyways). Remember, though, most of the size/weight savings comes from being an f/9 lens, so you're dimmer with less coverage. And while process lenses are "optimized for close-up copy work" and may have focus shift issues, this doesn't seem to be an issue in pictorial use, even by pretty demanding lf photographers.

One possible (though unlikely) disadvantage to a large surplus of coverage might be reflections outside the picture area inside the camera, but I've never had that issue.

Finally, as has so often been pointed out, the images made by the original Group f/64 photographers are still noted for their sharpness, even though they were made with what many today would classify as less-than-desireable lenses...

[swmcl]

Hi guys,

Thanks for the replies. Eric you make a good point about light inside the camera I assume a new camera will account for the extra light. Mark thank you for your thoughts too.

One thing to throw in the mix is the issue of mounting a Copal 3 shutter. I've got a feeling they won't fit a Shen Hao 4x5!

So I guess by the answers that the images might well be of an equivalent sharpness and that it comes down to brightness in focussing, image circle, weight, cost etc.

My original thinking was that a lens that had a massive image circle wouldn't be as sharp as a lens with a smaller image circle.

Cheers!

[Ron Marshall]

Hi guys,

Thanks for the replies. Eric you make a good point about light inside the camera I assume a new camera will account for the extra light. Mark thank you for your thoughts too.

One thing to throw in the mix is the issue of mounting a Copal 3 shutter. I've got a feeling they won't fit a Shen Hao 4x5!

So I guess by the answers that the images might well be of an equivalent sharpness and that it comes down to brightness in focussing, image circle, weight, cost etc.

My original thinking was that a lens that had a massive image circle wouldn't be as sharp as a lens with a smaller image circle.

Cheers!

Link to LF lens tests:

http://www.hevanet.com/cperez/testing.html

[Geert]

what i notice about wide angles is that, stopped down for focusing, the image circle is really small and hard to see the whole picture on the ground glass.

That has nothing to do with image circle but only with less light entering the lens. Image circle will not reduce when stopping down.

What you see as a smaller image circle, is rather the hot spot of the projected image.

G

[Brian Ellis]

what i notice about wide angles is that, stopped down for focusing, the image circle is really small and hard to see the whole picture on the ground glass.

I assume you focus this way because of the possibility of "focus shift." Have you tested to see if focus shift is a realistic problem? One of the lens gurus here who knows much more than I do about lenses can correct me if I'm wrong but it's my understanding that "focus shift" isn't much of a problem with modern lenses (by "modern" I mean from roughly the late '60s on, maybe earlier). I've made thousands of LF photographs without stopping down to focus and if it's a real problem I haven't noticed it. However, my oldest lens is probably around 1950, the rest were made somewhere in the 1980s or later.

[Rob_5419]

what i notice about wide angles is that, stopped down for focusing, the image circle is really small and hard to see the whole picture on the ground glass.


Cotdt -

you probably didn't mean that. The image circle is still around what the manufacturer says it is, but on focussing, only the centre of the image is illuminated due to the covering angle of light entry from the wide-angle lens.

Being myopic and of pensionable age, I find I can't focus a 65mm f8 under the darkcloth with any accuracy in the corners.

I certainly haven't thought about whether I would use a wide-angle lens rather than a standard lens, just to get higher quality on the image. Life's too short. By the time I've walked far enough back with a standard lens, to capture the same field of view with a wide-angle, I'd have stepped off from a cliff.

[Ole Tjugen]

what i notice about wide angles is that, stopped down for focusing, the image circle is really small and hard to see the whole picture on the ground glass.

I happen to have several lenses of the same focal length, from narrow-field Petzvals to superwide wide-angle lenses. I can assure you that at f:32, they are all equally dim on the ground glass. But if I replace the ground glass with a bigger one (i.e. putting the lenses on a bigger camera), it's easy to see that only the wide angle lenses have enough coverage for the really big sizes. So the image circle of a WA lens is larger, not smaller - and at the same aperture it's certainly not darker.