Overexposed negatives when tilting lens

[jasonjoo]

So I just got out of the darkroom (my second time developing 4x5 negs!) and noticed that on the photos that I used tilt movements, the negatives came out very overexposed (can barely make out the outline of someone's face). The first time this happened, I thought I had a bad batch of film (was using the film that was in the holders that I purchased... the previous owner said it was FP4 and wasn't in the fridge for an unknown duration of time).

The photos were taken indoors on Arista.EDU Ultra 100 4x5 sheet film. I was using my brand new Chamonix and new-to-me 150mm Sironar-S. Exposure taken from an incident meter was: 1/30th, f5.6, ISO 100. Bellows draw was roughly 7" to 8" and I did compensate a little bit for this. I developed the negatives in HC-110 diluted to 1:50 for 7 minutes @ 68º F.

5 out of 6 negatives turned out perfectly fine. It's the last one where I tried tilting the lens upwards to gain shallow DOF that came out very overexposed.

Any ideas? One possibility is that I hand tightened the retainer screw when putting the lens on the lens board. My lens wrench has not arrived yet and I was eager to put some film through my first LF camera.

Thanks in advance!

Jason

(Won't be able to scan samples in until tomorrow night... But I didn't even bother hanging the blown out negative to dry...).

 

[David William White]

Nah, more likely you didn't close the shutter before pulling the darkslide...or suchlike.

 

[Ian Grant]

Weird I replied to this, a few minutes ago.

Check the bellows, if you have pinholes in the corners these are far more likely to show up and affect images when you tilt the lens.

Ian

 

[argus]

Weird I replied to this, a few minutes ago.

sure it wasn't on LF.info?
Most likely due to the server upgrade.

G

 

[eddym]

Nah, more likely you didn't close the shutter before pulling the darkslide...or suchlike.

That's what I was going to say, but it sounds like he was shooting with the lens wide open anyway: "f5.6 at 1/30"

 

[David A. Goldfarb]

I think what David William White means is that he left the shutter open for focusing, put in the filmholder, and pulled the darkslide, without closing the focus lever on the shutter. I think that's a good bet.

An extreme tilt with a close up image can cause an exposure gradient (jbrunner started a good thread on this topic that you could turn up with a search) due to the difference in bellows extension from one end of the image to the other, but you wouldn't get an extreme overexposure from a tilt.

 

[darinwc]

"5 out of 6 negatives turned out perfectly fine. It's the last one where I tried tilting the lens upwards to gain shallow DOF that came out very overexposed."

-It's hard to tell if this was a user error or an equipment problem with a sample of only one negative.

Here are some possibilities.

Lens flare. You said you tilted the lens up. if this caught the light from the sun or sky, you may have had lens flare. You dont neccasarily need the sun to be in the frame, bright areas can cause lens flare or just the sun hitting the face of the lens. example: (there was a url link here which no longer exists)

User error. forgetting to close the shutter before puilling the darkslide. setting the wrong exposure. accidentally moving the aperture. etc.

bad shutter speed. some shutters are less accurate on certain speeds, usualy the slow speeds but that is no allways the case. They use different mecfhanisms for difffernt speeds.

Inconsitant shutter. Thick oil can cause slow speeds to be inconsistant or slow.

Light leak. Pinhole in bellows. bad light seal. warped film holder, darkslide opeing, etc.

 

[darinwc]

Or the light could have changed.

 

[donbga]

sure it wasn't on LF.info?
Most likely due to the server upgrade.

G

No another LF/APUG cross post. Not that I really care.

 

[jasonjoo]

Thanks guys. What's the best way to check if there is a pinhole in the bellows?

I'm almost certain that I did not leave the shutter open after I inserted the film holder. Well, a few times I did do this, but I caught them both times and discarded the film. But, I'll be a little more careful next time and see if I get the same results.

Jason

 

[David A. Goldfarb]

A pinhole will usually cause a faint secondary image if it's close to the lens, or some consistent light leakage if it's close to the film, rather than general overexposure, unless it's really large, in which case, it would have affected all six sheets shot under the same conditions.

To check for pinholes, take the camera into a darkened room, take off the back or the lensboard, extend the bellows, and shine a light inside. If you've got a planetarium, then the bellows needs mending or replacement.

 

[eddym]

I think what David William White means is that he left the shutter open for focusing, put in the filmholder, and pulled the darkslide, without closing the focus lever on the shutter. I think that's a good bet.

Hey...! That's one that hasn't happened to me yet! My time must be coming, I'm sure...!

An extreme tilt with a close up image can cause an exposure gradient (jbrunner started a good thread on this topic that you could turn up with a search) due to the difference in bellows extension from one end of the image to the other, but you wouldn't get an extreme overexposure from a tilt.

As the film approaches the edge of the image circle, there may also be a gradation caused by light falloff as well, but again, that would not cause overexposure, but the opposite.