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  #11  
Old 25th October 2021, 04:14 PM
Mike O'Pray Mike O'Pray is offline
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Quote:
Originally Posted by skellum View Post
Sorry John.
Here is where the Internet Forum falls down.
If we could meet in the pub I reckon we'd have thrashed this out by about the fourth pint of Guinness.
I agree. Sometimes on a forum where face to face comms are not possible, the only way to be sure what is the information required, involves the very long-winded way of asking a series of questions, awaiting an answer and taking it then in very small steps to be sure that what the person needs to know is what we are answering

pentaxuser
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  #12  
Old 25th October 2021, 10:42 PM
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Maris Maris is offline
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When changing contrast filters the question is what changes and what stays the same.
With the latest Ilford filters and their Multigrade Classic paper the exposure stays the same for grades 00 to 3 and asks an extra 9% or so for grades 4 and 5.
The highlights are the thing that stays the same and the shadows can be racked up and down as the paper grade changes. In theory.
This works for small changes in contrast but for a big change I'll run another test strip just to be sure.
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Old 26th October 2021, 08:37 AM
Alan Clark Alan Clark is offline
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My experience is different to Maris's. He says the highlights stay the same when the same exposure is given at different grades ( with Ilfords latest filters and Mgd Classic.) When I tried this a few years ago with Mgd.4 the mid tone stayed the same, and the highlights and shadows both changed. When going to a higher grade the shadows got darker and the highlights got lighter. More contrast. When going to a lower grade the opposite happened. The shadows got lighter and the highlights got darker. Less contrast. This was in a Leitz Valoy condenser enlarger and a traditional pearl bulb. I did the experiment then did it again with an LED of 2800K to see if it worked the same. It did.
Colour temperature of the lamp is important here. I used to use a fluorescent light in a home-made 5x4 enlarger. This worked as Maris has described. The highlights stayed the same at the same exposure with different grades.
If anyone is confused about this I would advise them to do a simple experiment. Next time you do a really nice print with no burning or dodging on, say, grade 2.5, make more prints with the same exposure. 1.5, 0.5 and 3.5. Then go to 4.5 with more exposure. These four prints will show you exactly what is happening, with your set-up. And my bet is that in the future you will always opt to do another test strip when moving to a higher or lower grade in order to try to get a better print, rather than keeping to the same exposure and hoping for the best.

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Old 26th October 2021, 09:11 AM
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I agree with Alan. If you look at the paper curves supplied by Ilford then they cross at the speed point which Ilford take to be a mid-grey. That is the tone that will stay the same with constant time and changed filters.

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