Blotchy pattern on 4x5 negatives

[StoneNYC]

Wow that's bad.

All I can say is carbon fiber isn't opaque and this is one of many reasons I now buy only new Chamonix holders.

Good luck everyone, perhaps Toyo will offer a replacement dark slide once they make non-opaque ones.

[marmot]

So I did another test to try to figure out the exposure threshold where light gets through the closed dark slide. I did 3 shorter exposures in direct sun (7500 footcandles) then 3 exposures in the shade (450 footcandles).

#1 - Sun, 1/2 second (not very precise, I just took the blackwrap shade away for a split second.
#2 - Sun, 1 second
#3 - Sun, 3 seconds
#4 - Shade, 15 seconds
#5 - Shade, 30 seconds
#6 - Shade, 1 minute

The patchy density can be seen on all sheets, even on sheet #4, exposed to light in the shade for 15 seconds. It's at a level that I might not have noticed by eye if I had taken an exposure with the camera (especially if there were no large dark areas in the composition), but it's definitely there.

I can understand taking precautions with the loaded holder in the direct sun, but if 1/2 second is enough to get light pollution then I don't if there's a practical way to keep it out of the sun enough on a day exterior (especially if the camera position is in the sun). I can keep the holder in a light tight bag but I still have to take it out and put it in the camera.

Even the contamination level at 15 seconds in the shade concerns me.

I'm going to email Toyo about this and see what they say.

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[marmot]

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#6:

[chacabuco]

Did you hear back from them?

[Jordan]

Very curious what they have to say

[bob carnie]

Very good sleuthing indeed Mr Scudder and Mr Barrett - who would have ever thought? I tip my hat to this exchange by both of you and to the OP for follow through on their advice.

I for sure thought it was bad agitation at first or film sticking some how .

[marmot]

Toyo says it may be a manufacturing defect so they're sending me new dark slides to test.

[Patrick Gauthier]

ooph that's terrifying, especially considering the short duration of exposure it takes to botch the negative (I can't really see a practical way to avoid the contamination, especially if you're in the field). I suppose those tests were done with 3 different film holders/sets of dark slides? Maybe only some of your holders/darkslides are screwy, and that's why you only see it some of the time. Did you purchase them all new on the same date? Maybe Toyo manufactured an entire defective batch (that would be terrible). It would be nice of them to send the film to test as well. . .

[marmot]

Patrick, I've seen the problem on at least one side of each of my 8 holders so I'm assuming they're all the same. Every one of my dark slides I've deliberately exposed to sunlight as a test has passed light through to the negative.

I bought them in 3 batches from B&H starting in January.

I think the reason I initially saw the effect on some photos and not others is because the holders were exposed to different amounts of light, and it may be that some of my "clean" negatives actually have minor light pollution that's masked by the details of the image.

[ctteg]

Amazing. I, too, just started shooting 4x5 with brand new Toyo film holders. I got the blotchiness too after shooting on a bright day. Not good. I purchased mine from B&H as well - earlier this year (2016). Great problem solving indeed.