Shutter Issue or Other Causes of this Kind of Overexposure?

[hanhasgotqi]

Hello all,

I would like to ask if the exposure issue shown below was due to possible shutter faults or something else. I recently started using a 40-year old Fujica ST801 film camera. The shutter seemed to have functioned normally for the first 3 rolls of films I tried.

However, for the latest roll, a Fujifilm Velvia 100, I noticed that the left third of the frame (or the bottom third of the frame in portrait position) appeared strangely more exposed than the other parts of the frame. For example, in the first picture below, I saw this strange transition from blue sky to a pale whitish sky from right to left. Almost as if I used a circular polarizer on a wide angle lens, except I didn't. I only used a UV filter and the lens was a 135mm telephoto.






In the second picture, I shot in a portrait position and again, the bottom third of the frame seems washed out with more light than the top part. The blue is more blown out and the mountain below seems overexposed. I almost feel there is some light leak for the bottom third. Have you guys seen any patterns like this before? Do you think there is something wrong with the shutter? The shutter is an old mechanical cloth shutter. It opens from the left side toward the right side and return to the left (looking at the back of the camera).

Or, perhaps there is something wrong with the UV filter I had on? The UV filter is a brand new Kenko RealPro filter produced in 2017. The altitude is at around 10,000 feet for these shots.

Another example of the difference in exposure across the frame:



Thanks in advance, guys! Great to experience the joy of shooting film again.

[Big R]

Perhaps the light seals are in need of replacement?

[Excalibur]

H'mm the first three rolls of film were OK you say which would suggest a development fault? Unless you were getting shutter lag because the camera is old and used at a low temperature? Any mechanism with just a trace of lubricant, dust etc would not work at best in very cold conditions and the trick is to keep the camera under your jacket and just pop it out to take the shot.
A silly question:- was the sky the same deep blue across the mountains (from left to right)?

[hanhasgotqi]

[cooltouch]

You might have a very mild case of shutter capping or shutter bounce. Probably the former more than the latter. Years ago, I had a Canon FTb that exhibited a more severe problem than what you're seeing. In my case, the right half of the frame was as dark as night. Turns out the FTb was suffering from shutter bounce, which the way it was explained to me was the shutter has a clutch mechanism that causes it to stay in place after it's tripped. If this clutch gets worn out, it doesn't capture the shutter properly and the shutter bounces back, partially obscuring part of the frame. Shutter capping is different, but I'm not at all sure I can explain what's going on in that case. I think it has something to do with the two shutter curtains traveling at different speeds, where the second catches up to the first too soon. But I'm not sure if that's the best explanation. Perhaps someone else here can explain it.

[Excalibur]

[hanhasgotqi]

[Excalibur]

[hanhasgotqi]

Thank you again for all your replies. I checked out some images examplifying shutter capping online. Theirs have a distinct cut-off area where the images become really dark. My photos above don’t look like those, I feel. The exposures above had been dialed down 1 stop in post. The originals were overexposed (quite obvious with Velvia slide film). Now I think about it, those few shots up on the mountain were the only few shots I took with this Fujica camera that were stopped down to f/16. I was following the sunny 16 rule. Images from the previous 3 rolls were usuaslly shot at f/8 or f/5.6, in overcast conditions.

When you press the shutter release on a Fujica ST801, a moving metal bar inside the mount will push a pin on the lens to close down the aperture, actuating your aperture setting. The metal bar on mine and its hinges have rust on them. They might have caused the aperture blades to close down just a tad too slow, causing the overexposure and uneven exposures across the frame. The problem might be too minor to show in not so bright conditions, but became obvious when I set the aperture to f/16.

Or, perhaps that particular lens has sticky aperture blades.

I’ll do some more tests to verify.

[Excalibur]

[Pentode]

What was the shutter speed on these shots? It looks bright, so I'm guessing 1/500 or similar. You may find the problem doesn't manifest itself at slower speeds.

[hanhasgotqi]

[hanhasgotqi]

I would like to report back that, although this old Fujica ST801 occasionally has shutter tapering/capping issue (1 frame every other roll), the exposure issue shown in the original post was caused mainly by a lens fault. The aperture blades in my Fujinon 135mm/3.5 could not be closed down quick enough. Sometimes not closing at all.

I also did the following tests. In 2 places, I made 3 exposures for the same composition in each place. The first exposure in both places was shot wide open at f/3.5, the shutter speed was at 1/1000th of a second. The second exposure in both places was shot at f/16, and the shutter speed was decreased accordingly to 1/60th of a second. The third exposure was the same as the second, except that I manually pressed down the DOF preview button so the aperture blades were closed down to f/16 manually before the shot.

The uneven exposures only appeared in the second shots in both places. It seems that the shutter was working fine for both the first and third exposures in both places. The gradation from light to dark in the second exposures was obvious. I checked the lens accordingly and the aperture blades are surely slow to react when closing down. Sending it in for a repair.

The pictures below are arranged accordingly, 1st, 2nd and 3rd exposures in both places:


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