A quick update, I have been working on the software end of things and have many improvements. I changed the conversion algorithm and it is 100x faster. It can now create images that when displayed in sequence will allow for 10 and 12 bit (~4000) levels of grayscale. The exposure module steps through them automatically. The software works with a USB power strip to control the enlarger light source. The monitor is turned off so you initiate exposure with the space bar.
Hi, where can I download the software?
Glad to see your success. Are you using the exposure software? I've attached some luts to use with it, the ilfordbasecontrast is calibrated for Ilford WT with no filter and works for most things. The gamma file is for making negatives, there is more about this in the digital negative forum. There is a lut generator on the third tab of the sotware, just create the lut file and apply your curve in photoshop to make your own luts.
The lut file is a tif with 255x255 (16 bit) grayscale values. You just apply your curve to it and reverence it when you import the file. If you look in the application resource folder you can examine the tif file used for the step wedge. It's a standard 21 step in 5% increments.
Creating curves is a big subject and many methods. I used this tool QTR step wedge tool. I just exposed strips dried them in microwave and photographed the result. It's not the most fun thing to do. https://www.quadtonerip.com/html/QTRdownload.html. Also, I've used the ilford warmtone lut with ilford classic without any issue, it hasn't seemed worth the effort to make one specifically for it.
Creating curves is a big subject and many methods. I used this tool QTR step wedge tool. I just exposed strips dried them in microwave and photographed the result. It's not the most fun thing to do. https://www.quadtonerip.com/html/QTRdownload.html. Also, I've used the ilford warmtone lut with ilford classic without any issue, it hasn't seemed worth the effort to make one specifically for it.
I can’t get paper white and full black with the lut
Am I right in thinking that I can derive the endpoints of your curve by the k values at the top and bottom of that lut tif file? I’m finding I can’t get paper white and full black with the lut - so I’m thinking I’ll start off with a straight line between those two points and move them apart a bit until I get a full tonal range. Then I’ll see if I need an actual curve in between.
That suggests insufficient density, which would be odd. I suspect you may have a light leak problem that reduces contrast.
That's the way to do it. Establish your white and black points then find middle gray, then half of that. Keep in mind the panel I have is almost two years old now and for all I know the manufacturer has tweaked the contrast in the panels or driver. There is no specification for continuous tone and this is entirely 'off label' use of these panels.
Now that you bring it up, I replaced the cold light with LED tubes, so I probably have more contrast on multigrade.
That's the way to do it. Establish your white and black points then find middle gray, then half of that. Keep in mind the panel I have is almost two years old now and for all I know the manufacturer has tweaked the contrast in the panels or driver. There is no specification for continuous tone and this is entirely 'off label' use of these panels.
Mines an incandescent Opal lamp, but yeah - quite probably I have less contrast with no filtration.
OK, that explains it; you guys are comparing apples & oranges.
As in any process, establish white & black points first, ensure there's no fogging etc, then linearize.
I need to determine the exposure that gives me a solid black at 0 density, then adjust the density of the highlights using the curve until I just get white at the other end.
That's one approach. The other is to take the full contrast range of the LCD as a starting point and select the contrast grade/filter that will give you a fill-scale print. Then use the curve to linearize the result. The advantage of this way is that it's less likely to result in posterization.
I'm surprised at your very long exposure times for this modest size print. But that's probably better discussed in a separate thread.
The curve looks like a good starting point. I have a feeling looking at the second print that there's some room for improvement especially in the shadows and midtones. Eyeballing is deceptive; it may work better to photograph or scan a step wedge and then plot the values in Excel.
the QTR tool doesn’t seem to have any capacity to use those readings. I guess I could try converting them to percentage of dmax?
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