ChartThrob Question

[rpiontek]

Hello - I tried to use ChartThrob to calibrate for printing on silver gelatin. After generating the curve, I applied it to the calibration chart and re-printed it. It looked pretty good to me, though it was not hitting the blackest black that it should.

Then I tried printing a negative of my own, and had the problem that there was banding in the highlights. What I mean is the transition from one light shade to another is very quick, as if there is a limited number of shades of grey.

Attached is a picture of the curve I got from ChartThrob.

Details about my process - using a cheap Canon ip4600 inkjet, and scanning with a DSLR. I think my lighting of the test chart is ok. I opened the RAW image in Lightroom, set the white balance, and zeroed everything else out.

My next step was going to be to adjust the contrast and exposure to get the initial contact print of the uncurved chart closer to what it should be, then generate a new curve. What do you think?

 

[sanking]

Hello - I tried to use ChartThrob to calibrate for printing on silver gelatin. After generating the curve, I applied it to the calibration chart and re-printed it. It looked pretty good to me, though it was not hitting the blackest black that it should.

Then I tried printing a negative of my own, and had the problem that there was banding in the highlights. What I mean is the transition from one light shade to another is very quick, as if there is a limited number of shades of grey.

Attached is a picture of the curve I got from ChartThrob.

Details about my process - using a cheap Canon ip4600 inkjet, and scanning with a DSLR. I think my lighting of the test chart is ok. I opened the RAW image in Lightroom, set the white balance, and zeroed everything else out.

My next step was going to be to adjust the contrast and exposure to get the initial contact print of the uncurved chart closer to what it should be, then generate a new curve. What do you think?

Your curve looks pretty normal, but looking at the histogram suggests significant clipping of tonal values in both the highlights and shadows. This probably resulted from the limited dynamic range of your DSLR.

Sandy