Chromega Dichroic VC Filters

[blevblev]

I just got through testing my Chromega D Dichroic II for use with VC paper. I followed the instructions in the book 'Way Beyond Monochrome." I'm posting my results here, but I have a question. The contrast range goes from -1.8 to 3.8. Are the results showing the lower contrasts as negative valid? I know that the below-the-lens Ilford filters have a "00" filter which perhaps is supposed to be less than zero.

Click on the thumbnail for a larger version:

http://www.largeformatphotography.info/forum/attachment.php?attachmentid=11530&stc=1&d=1207021685

[ic-racer]

How did you arrive at the contrast numbers? I use a chart, ie 00 = ISO 180 = 1.8 log units; etc...

Either way, your chart has the correct look to it. Again, depending on how you got your numbers, it looks like your -1 = 0 and -2 = 00, etc.

Here is the one I use for a D5500. Yours looks similar.

[blevblev]

I did 11 prints of my Souffer 4x5 21 step step-wedge using the recommended yellow and magenta values:

# Y M
1 170 000
2 144 003
3 124 005
4 105 010
5 085 016
6 065 026
7 046 039
8 026 065
9 013 092
10 005 124
11 000 170

then I plotted each one on a graph, and then measured each one with a "paper range and grade meter" from the book that looks like this:

http://www.largeformatphotography.info/forum/attachment.php?attachmentid=11547&stc=1&d=1207094533

[ic-racer]

So, it looks like that chart you posted from the book does not go down to '00', but I think your methods look sound and those lower contrast values you have do correspond to '0' and '00'.

You can do a quick and dirty double check of your step wedge prints. Since you have a 21 step wedge, just count the number of gray steps (ignoring the first and last faint ones) and multiply by 0.15. This will give you the contrast range without having to do the graphing. So, if you got 12 grays between black and white you would have 1.8 log which is 180 ISO which is about "00"

[blevblev]

Thanks, I'll do that...