Light source suggestions


#21

Sadly this isn’t really the case. DSLRs can correct for off white balance, but not poor colour rendering. When converting a negative to a positive, you’re already really pushing the amount of colour information you can get out of a narrow range. With a low CRI there just might not be enough information there. You may also see artefacts like green / magenta tinged skin, etc.


#22

A different alternative than a light table (and likely more money than many want to spend) is to repurpose an old colour enlarger. Colour enlargers have three dials to let you control the amount of cyan, yellow and magenta light coming out of them. Using these dials you can ‘dial in’ the opposite colour to the negative, cancelling out the colour cast in the image - meaning less post production as you just need to invert and do some curves adjustment.


#23

I noticed DSLR scanning color negatives works very well, but setting the correct exposure is critical and to get shots rivaling my dedicated filmscanner I need to take multiple exposures (‘HDR’) to get all the color detail.

Remember that white balance is done after the sensor stage in most / all cameras. So setting the white balance to correct some of the red / orange cast might help in previewing and taking your shot, but it will do nothing to the data captured in the RAW file.

So what happens is that you’re basically scanning your negative ‘as a positive’. Most good camera’s have 14 bits of precision, but mine has 12 for instance. Imagine you have a good 14bit RAW file, and you expose it perfectly (which means you are ALMOST clipping the red channel in the raw data), that means you’re using 14 bits of precision for the red channel… which means the blue and green channels have way less than that. Then you’re inverting, fixing the colors, fixing contrast… and yes you might end up with some posterization and / or banding because of the limited dynamic range you shot in the green / blue channels.

Like I said my (Sony) DSLR has 12bits of precision as far as I know. Let’s say I did not expose perfectly (because this is hard to do, you have no raw data histogram, so you have to try with trial and error at what settings you’re clipping and at what settings you’re not. And remember we’re talking about ‘clipping the raw data’ here, not the (preview) jpeg). So let’s say the best exposure I can manage without clipping any channels means I filled the histogram of my shot for about 50% to 75% percent. That means I actually used something like 11bits of precision for the shot… Just for the red channel. That means I only captured 6 to 7 bits of precision most likely in the green and blue channels and this causes issues. So that’s why I (and Filmlab too as far as I understood) is taking multiple shots to merge them together like HDRMerge does, so you can actually try to capture more dynamic range in all the channels than would be possible in a single shot.

Of course your DSLR camera has it’s own color response… but any scanner ($50 or $5000) is no different. That’s why people talk about calibrating then when you’re scanning positives.

But every scanner tool where I talked about this says that for negatives there is no (useful) color calibration. Since you’re taking all the channels individually and ‘lining them up’ while inverting to do the final color balance, the actual color-balance that your capture device introduces is (almost) irrelevant.

At least I have scanned negatives on my real film scanner and the same negative on my quite-old DSLR and when done properly the color output is exactly the same from the two, as far as I can see.

If you really dig into the Filmlab scenario and you’re scanning ‘positives’ (slides), then doing a white-balance check on the lightsource really does help in getting the color ‘pretty good’ right from the start. Of course if you want more precision, you have to think about calibration. Capturing an IT8 target with Filmlab (while white-balance set to your light-source) and then using a free utility like LProf to make an .ICC profile will help if you want to color to be more ‘perfect’.

But I don’t think the purpose of Filmlab is to get perfect calibrated color. I think it’s more about getting ‘usable results as easy and quickly as possible’


#24

I work at a radiology dept.There are one or two old fashioned light boxes knocking about from the days of x-ray prints which i’ll try.

If those don’t give me the right results i’ll spring for a LED light box.


#25

So much great discussion here guys! @jorismak makes really good points about the differences between color positive (slide) film and negative film. Both have their own challenges when scanning, but having a full spectrum color-balanced light source is probably more important for slides. Negative film was designed to be color balanced at the time of output, which originally meant darkroom printing but now can mean software color conversion.


#26

Wow, that’s bad! I can definitely say that neither of my LED light pads have had a visible grid like that.


#27

Really interesting discussion. This might be a very stupid question, but does B&W vs colour make a difference? I’m planning on mostly resurrecting my rangefinder and shooting B&W nearly exclusively - I’ll spring for a light box of I need to, but my original plan had just been to just my tablet.


#28

You can try a tablet. It helps (a lot ) if you manage to get some distance between the film and your tablet.

If it doesn’t work I really advise that Huion A4 tablet. It’s big enough for most sheet formats and the light is quite clean and even and it isn’t expensive at all. It’s only a few millimeters thick and is just a tiny bit larger than a sheet of a4 paper.

Any led source has a flicker in it, but if your shutter speed is slow enough you get perfect lighting.

On a phone (without an aperture to close ) you might get some flickering. I don’t know how that is fixable (ND filter for phone?:)), but I don’t think it’s going to be a big problem.


#29

Justed wanted to add I almost exclusively deal with 120 black & white negs.


#30

I was only thinking about the benefits of having a neutral light source as a starting point before inversion


#31

Just in case anyone else is wondering, The main difference between Huion A4 and the LS4 is the brightness and thickness. A4 is brightest light pad with the brightest light of 4480 Lux. And L4S has the brightest light of 1100Lux yet is thinner and charges via USB therefore is more portable (think of attaching it to a power bank and using it anywhere).

For reference the brightness of a standard copier is around 1400 lux (http://vitaleartconservation.com/PDF/light_levels_used_in_modern_flatbed_scanners_v1.pdf) but I couldn’t find any information about how bright a negative scan is.

So if you want to be able to scan in the field and save $15 try the LS4. Personally I am getting the A4 as recommended.


#32

Reporting back; got the Huron in the mail today and it isn’t as bright as my old florescent light box which results in the loss of details in the shadows. Going to return it and investigate some more.


#33

Fellow Film Labbies: I ordered and tested a light source that worked great. This is flat panel LED, plugs with USB Micro, very light, and has rubber feet on the bottom so it says put. The light is white and very even across the panel It does not have or operate with batteries. It is the WGHL Led Light Pad A2/A3/A4 Size Tracing Light Box/Light Table Super Bright with Adjustable Light Intensity. The link for the panel is:[Flat Panel Light Source] (https://www.amazon.com/gp/product/B01MEE6IYK/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1)

Example of the panel using Ektachrome slides from 1953.


#34

I got that panel too but I am not shure if it has a full color spectrum.
I can work too on the Multiblitz Dia copy panel which offers halogen light and a flash.

The Multiblitz and some other light tables use a 2mm thick white translucent acrylic “glass” plate to even the light. Of course film should get wet mounted or in a holder to not get newton rings.

I know a guy who digitalizes all his analog pictures with a digital camera. He uses a blueish filter to fight the orange mask a bit already before he takes the picture. He told me his results are better with this filter.


#35

So I used Luff and it seems to be a shutter speed problem. Fluorescent light flickers at 1/120 so the banding and the grids seemed to come from the meter adjusting to be faster than a full cycle the lights were pulsing at.

I messed with the shutter speed and threw a polarizer between the phone and the negative and that resolved the issue.


#36

Suggest using some negative holder that positions the negative away from the light panel. You want the negative in focus, the light panel out of focus. An inch or so might work, but separation may be difficult with the iPhone (tiny lens ==> lots of depth of field).


#37

Flicker is a big problem. Many fluorescents and LEDs flicker. Our eyes don’t see it, but the camera does. iPhone tries for short exposures when it can. My test shot with iPhone using a bright source was 1/500th. Flicker as 1/120th vs shutter at 1/500, could affect exposure.


#38

@mccmark Strange that checkered pattern. I have similar Tikteck panel on order. Will report on how it works.


#39

@jorismak on sensor range: Color negatives take in much more dynamic range in the scene, but render this in fewer stops in the negative. Shooting color negatives with my DSLR never fills out the histogram.

Color positives (slides) are a different matter. Take in limited dynamic range in the scene, but render this with very high contrast in the slide. Slides may have density Dmax=4, which is 10^4 or 13+ stops in range. I think multi-shot capture will be relevant for slides, but not necessary for negatives. Ditto for accurate exposure.


#40

What about the kindle paperwhite screen? I’m on holiday and can not test, but it does not seem to have visible pixels. Also is matte so it should not give reflections issue.