Is this bellows sag

[S.Charles]

Hi,

I have never experienced this issue before, but in a number of exposures I see this dark border on the bottom of my frame. This is in the negative as well as the scan. I only seem to happen when I am doing a tighter focus, when the bellows are extended more.

I have attached an example. I haven't done anything with this negative, hence the horrible color cast.

-S.Charles

[GPS]

Before you ask, why don't you check it for yourself? This kind of bellows sag you would be able to clearly see on the ground glass of your camera.

[Walter Calahan]

Did you use a compendium? If you did and it wasn't the proper length, you will see this result, too.

I use lens wraps, so when the lens is mounted to the front standard, I fold the wrap into a square, and place it under the bellows to hold up any potential sag. This way I always know where I placed the lens wrap, too.

[GPS]

Yes Walter, that is possible but in such a case, you would get the vignetting at least on two opposite sides of the picture - unless you use some movements. It doesn't seem to be the case of this picture, although it is hard to see because of the black background.

[Ari]

It certainly looks like bellows sag to me.
Best way to find out is to look directly; even if the bellows seem just out of the way of the light path, it can make a huge difference on the photo.

[E. von Hoegh]

Bellows sag. Do you have cut corners on your groundglass?? I usually peek through the corners of mine when using movements to be sure that a) I can see the entire aperture and b) the bellows aren't in the way of anything.

[lenser]

GPS,

The compendiums that I have used can be at least as flexible in every axis as the movements in a view camera. Many's the time I've caught myself with the top of the compendium out much farther than the bottom, assuring me a vignette on one edge of the frame and not the other. Looking at every inch of the ground glass just before inserting the film holder is your best friend to catch these errors.

[GPS]

GPS,

The compendiums that I have used can be at least as flexible in every axis as the movements in a view camera. Many's the time I've caught myself with the top of the compendium out much farther than the bottom, assuring me a vignette on one edge of the frame and not the other. Looking at every inch of the ground glass just before inserting the film holder is your best friend to catch these errors.

Yes, it is possible to tilt them but it is not their intended movement. To make just one side of the lens shade longer doesn't make a sense. In such a case you can also make the opposite side longer too, without vignetting and with a better overall shading efficiency.

In fact, if you make a lens shade longer, you should also make its opening bigger in order to get a more efficient shading. That is not possible with compendium shades. Therefore you can make the shade longer only to the point of not vignetting - and if that point is reached on one side, it can also be reached on the opposite side without vignetting. Tilting the shade's opening doesn't have any better effect than making both side equally long. Hope I'm clear enough in the description... :)
The tilting of the compendium opening is just a side effect of its capacity to make the shade longer or shorter but has no purpose in itself.

[lenser]

GPS

Your last sentence is of course, my point.

A compendium can indeed tilt, especially during attachment and later during flipping it out of the way to set the shutter controls and then returning it into shooting position.


There certainly is no desire for this effect in normal straight on shooting, but tilting does have a designed function if there are radical tilts or swings applied to the lens which could result in the shade...in a normal configuration....actually creating a one sided vignette unless one side is purposely tilted out of normal position to get that side out of the light path. Obviously, that also depends on whether it is attached to, and moves position with, the lens board or standard, or if it is otherwise attached to a non-moving standard while the lens can be moved independently.

Both scenarios are why it can vignette in one position if one forgets to make a final check before exposure.

[Adamphotoman]

After you have your camera set up look through the four triangular cutouts in the corners of the ground glass. You should be able to see any obstruction from that vantage point.
Grant

[S.Charles]

Thanks everyone for your help. I will definitely try some of the things mentioned here.