Heliopan makes 105mm hoods in rubber or in short or long metal types.
The last thing a properly set and adjusted compendium does is vignette. That is the beauty of a compendium - it can make the same movements as the front standard and only the light that actually exposes the image can reach the film. All extraneous light is blocked from reaching the film.
" The last thing a properly set and adjusted compendium does is vignette".
That's sure - still you have to now how to set it properly! - "extended as long as your bellows" - measured from where?
"All extraeneous light is blocked from reaching the film" . A complete nonsense - no lens shade can block "all extraneous light " reaching the lens (hence also the film in form of the flare). It would need to be as long as to reach the flare causing light source! Difficult to have in case of the Sun or even any other light source...
In your "all extraneous light blocking" shade you forget to take in account the lens entrance pupil diameter - very important for the calculation of the lens shade opening!
"no lens shade can block "all extraneous light ""
Of course a klens hood can't. But a properly adjusted compendium can.
To all those who dream about 100% efficiency in blocking "all extraneous light" from falling on your lens - no matter how you adjust your compendium there are always light rays that are not seen by the lens angle of view but falling on the lens surface thus causing some flare. If you wanted to block (with Bob's 100% efficiency) also these rays (100% of them!) you would need to put the compendium frame right there where they originate. A question of geometry...! As I said before - the lens entrance pupil diameter comes to play - forget the film opening frame dimension "extended as your bellows" theory.
Didn't we have this discussion some year ago...?
"no matter how you adjust your compendium there are always light rays that are not seen by the lens angle of view but falling on the lens surface "
George,
There are many things sold for cameras called compendiums. Some do exactly what I claim. Others do not.
In Linhof's case there are two current compendiums for a Kardan and one each for a TK or MT. The Kardan Pro Compendium 001935 is primarily used for studio work. It attaches directly to the back of the front standard and has a set of masking bands. These bands, along with the extension of the compendium's bellows, allow you to mask off all light except that exposing the actual image.
The compendiums for the MT and TK have shorter bellows, mount directly to the top of the front standard and accept accessory masking blades to accomplish the same thing.
For the M679, M679cc and M679cs Linhof offers two bellows systems, one a Pro system with the masking blades and one a basic system that also accepts masking blades.
It is important that the front end of a compendium can be masked down to either the exact size of the film area (if your compendium bellows can be extended as long as your camera bellows) or to the same shape as your film if your compendium bellows is shorter then your camera bellows.
It is apparent that any compendium that you have used does not have these features. If your compendium opening is not the size of or the shape of your film you can not block all the light. In that case your comment would be correct. If it can be masked and has full movement capability then my comments are correct.
Bob,
you still don't understand the geometry involved in the theory of lens shades (or compendiums, - whatever because the theory is valid in the same way for both cases).
Even if your compendiums allow you to mask the lens view angle to "the exact size of the film area" it doens't mean AT ALL that you eliminated all the flare causing rays falling on the lens.
Shape it as you like, the compendium cannot eliminate these rays completely.
I'll try to explain it. Take your super duper Linhof xx compendium and shape it as you like. Now imagine a lens cone comming out of the lens, created by the lens angle of view. Whenever the compendium touches or even encroaches (because it's not circular but square or oblong or whatever) the virtual lens cone there you have the light limiting edge of the lens shade. Find whatever point on this edge, touching the lens view cone. Make a line from this point let it pass through the cone's axis and join it with a point on the lens' entrance pupil rim on the opposite side of the line's plane (i.e. for ex. if the frame point is up right the rim point is down left). Now create an imaginary cone (or a pyramid if the lens shade isn't circular) by rotating this plane around the point where it passes through the optical axis. This second cone (or a pyramid) will ALWAYS be bigger than the first cone, created by the lens angle of view. Now comes the worst - whatever light source present in the space between the greater cone and the smaller cone is a light which the lens doesn't see but vhich causes lens flare!
To continue: this space where all the light source creates flare, you can make it smaller by putting the lens shade further away from the lens but that will only narrow the space - never eliminate it. Unfortunately, the longer the distance between a lens and the shade edge is, the less you diminish the space.You can eliminate the space only by going further and further away with the shade edge up to the point where it will pass by the light source...
That's the reason that you can never have a complete elimination of flare with whatever lens shade or a compendium. The good news is that at a certain length away from the lens the shade has already such efficiency that it eliminates the majority of the flare causing light, except for the light that is too close to the lens angle of view.
Well, I hope it makes sens...
"The longer the distance between a lens and the shade edge is, the less you diminish the space " - i. e. that prolonging the distance more and more brings just smaller and smaller changes of the space...For a lens shade put at 1m and a one (proportionally bigger) put at 2m distance the shade's efficiency increases much less than for shades put at 10cm and 20cm respective.
I use a darkslide. I also have a bunch of pictures of darkslides.
The movie industry uses a thing called a french flag, which is basically a darkslide on the end of a flexible rod. I've never seen a smaller version for the LF folks. Maybe that clip that Calumet sells would work or be a good starting point for a solution.
From what we read above, maybe it's impossible anyway.
Let's keep it real, folks. This isn't NASA. Tom is looking for a practical solution, not optics theory.
my picture blog
ejwoodbury.blogspot.com
Yes and not, Eric. You can take everything easy or seriously. But a good lens shade or none or a bad one makes much a greater difference than a coated or not coated optics! The point is that flare is not only what you see on the gg or the final picture. Flare that you don't see on the gg can still take away the saturation and contrast in such a way that it makes a very visible result on the final picture. The reason why the film industry uses good lens shades is a serious one - without it the screen would be one class worse. In photography it can make a difference between a washed out white rose and a white rose with plenty of shades of white...
The reason why LF photograpers often don't use lens shades is a half from ignorance and a half from the fact that there are not too many good ones to choose from... All the talk about the slide (T-shirt, hat etc.) shading a lens belongs to the first category - only a few professional lens shades belong to the second one. I believe that the types Bob speaks about are good ones - although not as good as those I computer calculate exactly for my lenses ;-) ...
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