C7700 Colour Filters

[max_barstow]

<p>Hi,<br>

This sort of relates to my last forum, about an LPL C7700 enlarger- I ordered it (not arrived yet), but have used one before, and know it's got a colour head, so I don't neccesarily need MG Filters.</p>

<p>To get equavilaent filter effects with just the colour head, what numbers do I need to dial in on the enlarger for grades from 00-05? And I guess that changing the numbers will also effect how long the exposure needs to be?</p>

<p>Cheers</p>

[bob_sunley]

<p>Look at the product info sheet packaged with the multigrade paper you have. That info is usually on that piece of paper, or on the makers web site.</p>

 

[photo_smith]

<p>I think the LPL uses similar numbers to the Kodak filters, Durst were different.<br>

Kodak values:<br>

Grade 1 68Y 10M<br>

Grade 2 42Y 32M<br>

Grade 3 23Y 56M<br>

Grade 4 6Y 102M<br>

In reality though I find I rarely used the yellow filters at all for the higher contrast grades.</p>

 

[chris_waller]

<p>Follow this link to Ilford's PDF, and scroll down to page 3.<br>

<a href="http://www.ilfordphoto.com/Webfiles/2006130201152306.pdf">http://www.ilfordphoto.com/Webfiles/2006130201152306.pdf</a></p>

<p> </p>

[max_barstow]

<p>Thanks Chris, that link's exactly the thing I needed, one thing though; how do I compensate the exposure time for this? Do I just change it as if I were using normal filters i.e. doubling it when going from a value of 2 to 4?</p>

[chris_waller]

<p>The theory of the two-filter approach is that the total density remains the same across the grades so the exposure time remains the same.</p>

[max_barstow]

<p>Oh!<br>

Well that makes life a lot easier.</p>

<p>One FINAL thing about the use of mixing different grades-if you do half of the exposure at say, grade 1, and then the rest at grade 5, what's the point of something like that? I've heard talk of people doing that, but haven't really understood the purpose.</p>

[frank.schifano]

<blockquote>

<p>The theory of the two-filter approach is that the total density remains the same across the grades so the exposure time remains the same.</p>

 

</blockquote>

<p>Well, that's the theory anyway. In practice it doesn't always work out so neatly. Best thing to do is get a step wedge and make contact prints of it using different filter settings, but also using the same f/stop, head hight, and exposure time. Note the differences where the first black point lies under the different filter settings. That will tell you exactly how much more or less exposure you need in stops within 1/2 to 1/3 stop. Easy to figure out timings from there.</p>

[max_barstow]

<p>What's a step wedge?</p>