Help with copying medium format B&W negatives

The lockdown has given me the chance to go through some old B&W medium format negatives of mine (and a few made recently, after 15 or so years) trying to copy them with a digital camera (my trustworthy Pentax K20D) and a macro lens (namely the Sigma 105 macro lens/f2.8) both set up on a tripod and with my Android tablet and an application called Lightbox (to do what the name suggests). To my surprise though, the shots came out with a green grid, which I cannot explain. The grid is more apparent in the darkest parts of the negatives (photos provided as an example)
Could somebody explain why this happens and how it could be solved? I would be really grateful!
Thank you in advance.


Could somebody explain why this happens and how it could be solved? I would be really grateful!
Thank you in advance.



Dear Tianshi_angie,
Thank you very much for your kind interest and the suggestions you made. I have also thought of turning the green cast to greyscale but I suppose that the grid would still be there. I have copied an enlarged version of one of my photos I was asking about and I hope that it will be more visible now. I tried to convert the negatives to positives in two ways: one with Lightroom CC and the other with a preset program for Lightroom (only the free version just to give it a try) under the name Negative Lab Pro. Here is an enlarged part of the photo, which, at least on my computer, makes the grid visible. I hope it works
Best greetings from Patras, Greece

Thank you very much for your kind interest and the suggestions you made. I have also thought of turning the green cast to greyscale but I suppose that the grid would still be there. I have copied an enlarged version of one of my photos I was asking about and I hope that it will be more visible now. I tried to convert the negatives to positives in two ways: one with Lightroom CC and the other with a preset program for Lightroom (only the free version just to give it a try) under the name Negative Lab Pro. Here is an enlarged part of the photo, which, at least on my computer, makes the grid visible. I hope it works
Best greetings from Patras, Greece


ahh, I know what that is, its the individual pixels from your tablet, thats quite an easy one to fix if you have something to diffuse the light with (a sheet of tracing paper, a portable diffuser, sheet of muslin or something like that) to effectively blur each of the pixels on your tablet
making it greyscale will keep those gridlines
have you tried a gaussian blur on your photos?, that might help too, if you cannot diffuse the light from your tablet.
hope this helps
making it greyscale will keep those gridlines
have you tried a gaussian blur on your photos?, that might help too, if you cannot diffuse the light from your tablet.
hope this helps

I bought a small simple led sunken light fitting and made a wooden holder. I rest my negs and mounted slides on its lip (the negs held in place by a piece of 6x6 slide mount glass) and copy them in colour or black and white or both with my dslr or sony A6000. I use either hand held or tripod mounted depending on aperture needed to get round depth of field or slight film curvature. Trial and error works best for me as the cost per exposure ceased to be a consideration with the end of mass film usage. Any colour caste from the light source can be easily corrected in software. A taste for the more "arty/abstract" side of our magnificent obsession means I can use the images to work on even if a little unsharp or even dirty!