Why am I getting unexposed area on 4x5 sheet film?

[Doremus Scudder]

There are a lot of possible scenarios for the bellows to impinge on the image area. Bellows sag usually happens in the middle of the camera when using lots of extension. It causes an unexposed area at the top of the projected image, i.e., the bottom of the scene when viewing the image right-side-up. However, when using lots of rise and shorter lenses, the bellows on many cameras will creep up near the back at the bottom of the ground glass, causing a blockage at the bottom of the ground glass/top of the image when viewed right-side-up. This is a distinct possibility for the OP's problem, as is possible vignetting from the compendium shade. Both of these phenomena are difficult to see when focusing wide open, hence the advice to check at taking aperture, either observing the ground glass or looking back through the lens at the ground glass.

Doremus

[ShannonG]

Yup,,what everyone else said... Do a proper test session..
--Same subject like a brick wall to see the movements
--with and without movements (big movements so you know the capability of your set up)
--with and without the lens hood
--long bellows and short bellows
--wide open and closed down
-- if you put a grey card on the wall and meeter that ,you can also practice your zone placement at the same time
--TAKE A LOT OF NOTES

its just beginner stuff but by shooting a hand full of test negs now will save your images in the long run and you will know your set up and method better.

[Paul Metcalf]

I understand but the vignetting is at the top of the image so the bellows would have had to rise up into the light path.

No the top of the image shown by the op is at the bottom of the film holder which is on the downside of the camera in the back, so this is actually possibly the bellows sagging into the image area from the top of the camera, which shows at the top of the image because it's flipped (or rather rotated) to the bottom. Is it not common knowledge what happens to an image when it's projected through a lens? The reason you see the image upright in a 35mm or maybe some medium format cameras is because there is a mirror that's inverting the image before it appears in the viewfinder.

[richardman]

richardman, the attached image is what you see under the dark cloth with a large format camera. Bellows sag could cause the blockage at the bottom of the image (which because of image inversion - actually rotation - is the top of the developed image), and the slight twisting is not uncommon for a lot a bellows (resulting in the slanted line).

I never have bellow sag that affects the bottom of the image path, only the top. I will keep that in mind.

[Tracy Storer]

By the time the image exits the lens, to pass through the bellows, it is already upside down. The problem is either the inside top of the compendium shade, or the inside bottom of the bellows. The water is getting very muddy here, needlessly.

No the top of the image shown by the op is at the bottom of the film holder which is on the downside of the camera in the back, so this is actually possibly the bellows sagging into the image area from the top of the camera, which shows at the top of the image because it's flipped (or rather rotated) to the bottom. Is it not common knowledge what happens to an image when it's projected through a lens? The reason you see the image upright in a 35mm or maybe some medium format cameras is because there is a mirror that's inverting the image before it appears in the viewfinder.

[Jim Andrada]

I've had something like this when the lining of the bellows was getting old and popped up a bit at the bottom of the camera and I just plain missed it because I was being hassled by the property owner just as I was about to make the exposure. - I was on the edge of the street outside his fence and I'd already poked my head into the office and been told it was OK to photograph there, but the guy who was yelling at me had just driven up. Anyhow he calmed down, I took the picture and then went in and had a nice chat with him and his partner for a half hour. I took them a nice print but they'd gone bust and left.

Anyhow, a bellows or compendium issue seems like the most reasonable explanation.

[richardman]

Everyone who uses a view camera probably knows the image is UPSIDE down. It's on the ground glass. The only confusion really is that a bellow sag can affect the top of the bellow (the bottom of the image) which has been my only experience, or I suppose if the front standard is lowered, then the bellow sag can affect the bottom of the bellow (the top of the image) which I have not experienced myself and didn't realize it could happen and I am glad to learn that. Things only get muddled because assumption was made about view camera users not knowing the image is upside down.

[Hao]

Hello everyone~

Once again, all the comments are very appreciated and you people have been a great help.

So I went out and did some tests mentioned above as well as paid attention to the details in my workflow. The verdict is out: All of which mentioned are true to my circumstance.
First, the ground glass on my Wista Rittreck in particular is rather bright and clear in the centre according to my angle of view, on the second examination I realised that it was me who neglect the bottom of the ground glass.

The shaded area was caused by both the sun shade and the front tilt movement (upward). Occasionally I only looked through the ground glass using the built-in pop-out hood, and that spelled the trouble since the little hood didn't provide
the healthiest viewing experience.

The compendium sun shade, on the other hand, was another cause of the matter. As people have pointed out, when viewing with wide open aperture at f5.6, the situation was barely recognisable until stopped down few stops. It has also
come to my attention that after changing composition, whether that includes tilt, swing, shift, etc...I need to check the sun shade again and adjust accordingly should it gets in the way.

All in all, it's a valuable lesson to learn. Most importantly, it's great to know the class is supported by so many people here on the forum. Thank you!


Hao

[Regular Rod]

A while ago I eschewed the loupe in favour of a pair of powerful +5.5 reading glasses that cost only £8.95 including P&P on eBay (item # 271669873654). These make it easy to check all the composition and corners and edges simply by wearing the glasses and using a dark cloth. They are so effective that even at f64 it is possible to check every part of the image. That lens shade encroachment would be spotted immediately with this method, it has saved me from deploying just a tad too much rise on more than one occasion.

RR

[Hao]

A while ago I eschewed the loupe in favour of a pair of powerful +5.5 reading glasses that cost only £8.95 including P&P on eBay (item # 271669873654). These make it easy to check all the composition and corners and edges simply by wearing the glasses and using a dark cloth. They are so effective that even at f64 it is possible to check every part of the image. That lens shade encroachment would be spotted immediately with this method, it has saved me from deploying just a tad too much rise on more than one occasion.

RR

Sounds good in your situation!
I am already a spectacle wearer myself, not sure how the two should stack up though...

Thanks~