Quote Originally Posted by MajorGlory78 View Post
Hi all,

Another day, another issue

I've learned a lot, which is good:

- I was rinsing to hard, this caused damage to the collodion
- Less developer means a more 'even' image
- The collodion I use seems to work best when measuring roughly for ISO 1 (I know the issues with metering in daylight depending on the amount of UV that is actually there or not). This is remarkable, because the manufacturer of the collodion claimes ISO 3-5. What could be the case is the fact it was very, very cloudy here the last days. Since clouds do seem to block a LOT of UV light, this might explain why my current images are working when treating them as ISO 1. On a sunny day, the ISO 3 claim could very much be true I guess?


But I can't seem to get the results I expect. The images that are good seem to be to dark to my eye. I will add two images to demonstrate what I mean:

The first image is direcly from my scanner (unvarnished). The image is pretty 'clear': Even tonality, details present, full of contrast. But I'd like to get the images less dark.
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When working with digital, I would simply correct the curves, which (again, only to demonstrate) I have done in gimp. Which results in the second image:
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What I don't yet seem to understand is: Should I expose longer? Or should I develop longer? I am hesitant to develop longer with the developer I use, because as we figured out earlier in this thread, as soon as I seem to hit that 12-14 second mark when developing this much feared 'fog' appears.....

I have tried both. As soon as I extended either the development time or the exposure time the jug lost all details or even 'vanished' against the background....

Any hints? Thanks again for your time!
1) I don't use a light meter. I recommend that you learn to estimate the amount of time needed for correct exposure. Experience will guide you well. The problem with a light meter is that it doesn't measure UV, which collodion is most sensitive to, so you wil find that your meter is misleading you a lot under certain lighting conditions.

2) I think 1ASA is typical for most standard collodion recipes. By the time the collodion has aged 4-6 weeks, expect that value to drop by half

3) Your sample image gives me the impression it could have received another 1/2 stop of exposure. You shouldn't increase development time to compensate for lack of exposure because all you will do is quickly approach the point at which you're developing out unexposed silver, fogging the plate. Keep development times consistent. If the plate is too dark, make another and increase exposure.

I am wondering if you're trying to compare your image results to standard developing-out paper prints? Tintypes do not have the same tonal range: the lightest values will always have density (if you wish to retain details) that appears dark compared to a modern paper photograph.

That said, if you are not getting bright enough high values, there are a couple of things to consider. The first is: the age of your collodion. As collodion ages, the contrast increases. So if your collodion is only a few weeks old, you'll find that it gets more contrasty and the whites appear brighter once its aged another 4-8 weeks. Having some older collodion around can be useful when you want extra contrast.
Secondly, you can experiment with adding small amounts of Saltpeter (Potassium nitrate) to your developer, which will give a boost in brightening the whites. You can read about it here Read the whole article, but pay special attention to the part titled Developer Research. Finding the right amount of Saltpeter to add to the developer may take some trial and error on your part, but the recommendations in that article are a good place to start.