When is the Circle of Illumination too large?

Clueless · Jan 28, 2006

What is the balance between "movements" and flare? An eBay sellers' response re a 355 MM SK Symmar (convertible 620 MM) was an off-putting (to me) (it allows maximum use of tilts and swings on 4/5). IMO yes, if I were shooting Mt. Rushmore from the next state or The Washington Monument; but I am Clueless, really; thus the question.

ChuckP · Jan 28, 2006

You can just use a lens hood to cut off coverage to that required by your setup. This should help with internal reflections.

David A. Goldfarb · Jan 28, 2006

The usual tradeoffs are between coverage, internal flare, and the physical size and weight of the lens. You can eliminate bellows flare with a compendium lens shade, or significantly reduce it with an ordinary lens shade (something like a Hama adjustible rubber zoom shade is a nice compromise between a compendium and a regular shade). A lens in a Copal or Compur #3 shutter might be more than you want to carry or that your camera can support easily, but that's something you can decide for yourself. If you want a more compact lens in that range for 4x5", something like an Artar or G-Claron is perfect. It will be sharp and has plenty of coverage. The focusing aperture won't be as large, but with longer lenses this isn't as much of a problem as it is with wide lenses, since the illumination will be more even across the groundglass.

Bob F. · Jan 28, 2006

As others said, if the coverage is much more than you need and you are worried about light bouncing off the inside of the bellows, just use a lens shade. I use a self-supporting collapsible bellows shade from a local supplier, but there are a couple of them on the market (Cokin and Lee supply them I think). Very useful.

Cheers, Bob.

rbarker · Jan 28, 2006

I think having too much coverage is on par with having too much money or being too healthy.

As others have noted, use of a good lens shade pretty much eliminates internal reflections that might result from a larger cone of light coming from the lens. Excess coverage for 4x5, however, will allow greater movements, should you need them, or potentially using the lens on a larger format.

Frank Petronio · Jan 28, 2006

What they are saying, in case you are a slow learner like me, is that you need to use the shade to cut into the actual lens coverage area, not just keep reflections off the front element. Having 11x14 image circle on a 4x5 lets a lot of extra light inside the bellows to bounce around....

John Kasaian · Jan 28, 2006

It is my understanding that the Circle of Illumination occurs when the Circle of Confusion learns where the brandy and cigars are kept.

Of course I could be wrong, but its a better story.

rbarker · Jan 28, 2006

John - while the Circle of Illumination (aka glow) of which you speak is enjoyable, I've found it better to enjoy that after the photography is completed.

Clueless · Jan 28, 2006

Your experience does me a lot of good. Thanks.

I just imagined all that light bouncing around inside the bellows and knew that was the quick way to have a $5 lens out of a $500 lens.

Dan Fromm · Jan 28, 2006

Clueless said:
What is the balance between "movements" and flare? An eBay sellers' response re a 355 MM SK Symmar (convertible 620 MM) was an off-putting (to me) (it allows maximum use of tilts and swings on 4/5). IMO yes, if I were shooting Mt. Rushmore from the next state or The Washington Monument; but I am Clueless, really; thus the question.

355 mm lens? 4x5 camera? Not to be too clueless myself -- that's your screen name, not mine -- but does your camera have enough bellows to focus a lens that long? And, to echo a question I've been asked since I started shooting a 480 on 2x3, what good photographic purpose does a lens that long serve?

I shoot 2x3 with lenses made for much larger formats. Have never had problems with bellows flare, would be inclined to regard it as 100% myth EXCEPT that most of my longer lenses for larger formats are front mounted on a Copal #1. That being the case, perhaps the shutter vignettes the outer section of the cone of rays projected by the lens.

I have had one lens, a 12"/4 telephoto, that causes a bellows related problem. Its back focus is ~ 85 mm; with it at infinity on my little 2x3 Speed Graphic, the bellows is nearly completely compressed. And the lens' exit pupil is far forward. The effect? The compressed pleats cut off the outer couple or three mm of image. They're not a problem with near subjects.

If the price is right and you can use the 355 Symmar, why not risk it? If it doesn't work out you can always resell it.

David A. Goldfarb · Jan 28, 2006

You only know if bellows flare is a myth if you've tried side-by-side comparisons of the same image with and without a compendium shade that limits the image circle to the minimum necessary for the image. The effect can vary depending on the design of the camera and bellows and the scene.

df cardwell · Jan 28, 2006

Anybody but me ever set a bellows on fire on a sunny day,
not minding where I was swinging the lens ?

.

David A. Goldfarb · Jan 28, 2006

df cardwell said:
Anybody but me ever set a bellows on fire on a sunny day,
not minding where I was swinging the lens ?

Make sure Q-T Luong knows about this, so he can add it to his list of potential LF blunders--

http://largeformatphotography.info/mistakes.html

Frank Petronio · Jan 28, 2006

There is another myth or truth that using a 5x7 or larger camera with a 4x5 reducing back increases contrast because the larger bellows sucks up some of that extra light bouncing around. Who knows if that is true either?

David A. Goldfarb · Jan 28, 2006

Frank Petronio said:
There is another myth or truth that using a 5x7 or larger camera with a 4x5 reducing back increases contrast because the larger bellows sucks up some of that extra light bouncing around. Who knows if that is true either?

A friend of mine who went from a 4x5" Tachi to a Deardorff Special, which is a 5x7" camera with a 4x5" back said he felt he was getting better contrast with the Deardorff.

I've noticed I don't get flare along the edges of the frame with the Sinar and it's oversized square bellows, which I've sometimes had with my Gowlands and their rectangular, compact tapered bellows.

df cardwell · Jan 29, 2006

Frank Petronio said:
There is another myth or truth that using a 5x7 or larger camera with a 4x5 reducing back increases contrast because the larger bellows sucks up some of that extra light bouncing around. Who knows if that is true either?

No myth.

When folks used uncoated and single coated lenses,
when films were prone to halation and color contamination,
the ultimate portfolio showpiece was a white set with a red rose in the center if the picture. Really, almost as hard to photograph as a full bottle of scotch.

The problem of stray light inside a camera, be it a Hasselblad, Nikon or view camera, is a real problem.

Compare a 4x5 image made from a 90 mm lens, say, from Tachihara and one made on an 8x10 Deardorff w/ a 4x5 back !

Dan Fromm · Jan 29, 2006

David A. Goldfarb said:
You only know if bellows flare is a myth if you've tried side-by-side comparisons of the same image with and without a compendium shade that limits the image circle to the minimum necessary for the image. The effect can vary depending on the design of the camera and bellows and the scene.

David, as I said, I'm getting substantial vignetting behind the lens. Comes to the same thing as vignetting in front of it, doesn't it?

Cheers,

Dan

When is the Circle of Illumination too large?

Clueless

ChuckP

David A. Goldfarb

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Bob F.

rbarker

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Clueless

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David A. Goldfarb

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df cardwell

David A. Goldfarb

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Frank Petronio

David A. Goldfarb

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df cardwell

Dan Fromm

When is the Circle of Illumination too large?

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