Advice sought on colour cast mitigation with my setup, please!

Hi, I wonder if anyone might be able to advise me on an issue I’ve come across with my scanning set-up that is giving my scans a colour cast. I mean, I know why there IS a colour cast… I’m just not sure what to do about it.
My light source is a new Aputure AL-MX. I have turned the box it came in into a lightbox, with a hole cut out of it for the light to shine up through, and some little holes in which to sit the little feet of the Essential Film Holder on top to keep it from moving about. It works quite well! Only problem is, the box of the Aputure AL-MX is of a creamy-yellowy colour both inside and out. I feel that is the cause of the colour cast, as the light is bouncing around inside this creamy-yellowy lightbox before coming out to shine through the film.
I thought to spray paint the inside of the box with white paint, or even perhaps a neutral grey paint. Does anyone have any thought on that?? Many thanks in advance :slight_smile: Paul

Hi @paulkiss , welcome to the forum!

I presume that internal reflections of your light box are relatively negligible in comparison to the direct light from the AL-MX. Light shining on the negative from the lens/camera side is a different story though.

Take a few shots with your setup and no ambient lighting (darken the room) and see if it changes anything. Also, negatives can be difficult depending on initial processing, age and how they were stored, it might therefore be a good idea to take shots of different negatives, preferably from different films, too. Be sure to follow advice from this page.

If this does not help, post one of the shots (use a sharing platform like wetransfer or whatever is within reach) so that we can see what we can do with different setups.

I think you hit the nail on the head. The Aputure is a great little light so why hide it away in a box that’s going to introduce a colour cast? Why not make a mask out of matte black card the same size as the top of the Aputure and then cut a hole in the mask the same size as your film holder and then put your film holder on top of the mask so that light only goes through the film holder?
Room lights are always a potential problem too so they should be dimmed right down.
Personally I avoid all those problems by using a bellows with slide copy attachment. That way the light for the exposure is allowed to illuminate only the negative and all other light is kept out by 1. the bellows connecting the slide copy attachment to the lens and 2. the bellows connecting the lens to the camera thus avoiding ambient light getting to the negative and/or preventing stray light bouncing around causing flare/loss of contrast in the lens.
Hope that helps.
Excellent bellows like Nikon PB-6 + PS-6 can be bought on ebay for less than the cost of your light and really are an all in one solution. Camera adapters (if you don’t use Nikon) are also cheap and readily available.

I agree with Belinda’s suggestion of using a simple mask made from black card/heavy construction paper. That way, the only light is the pure light coming out of the lamp.

Agree with others that you need a setup to minimize ambient light falling on your film. But regardless of your setup, the last thing to do before you put film in the holder is to turn on your light source and set your camera’s white balance. Nikon calls it Preset Manual. Or, if you’re digitizing color negs, zero your white balance on a blank area of the film while it’s illuminated by the light source.

Yes, the inside of your box should be painted a true white (no optical brighteners in the paint). Lining it with a matte white card stock that is not coated with optical brighteners works, too.

Be sure the light is diffused evenly over the entire surface of film. The diffuser should be translucent, but milky enough to completely diffuse the light. It should be at least two inches behind the negative plane.

If your images show banding, it is due to flicker from the source. Either get a better source, or use a shutter speed slower (longer) than the power line frequency.