Banding problems with digital copy camera and fluorescent light source

I disposed of my scanners (two monster SCSI beasts I had to give away) and set up a copy stand for prints. In the past I had digitized a few negatives and transparencies by shooting up into the enlarger with a digital camera mounted at the lens stage. Now I have moved up to a 24MP Fuji and figured I would set up to use it on my two Beselers, one a 4X5 with color head and the other an 8X10 Beseler conversion.

First I put a recent 8X10 negative in the 8X10 cold light Beseler and exposed up with the Fuji kit zoom. For a first attempt I thought the result was pretty good and even posted it here on the bridges thread. See below. Then I bought a used 50mm Micro Nikkor and Fuji adapter, thinking it would be much sharper, and it was, but that's when I first noticed the banding running across the image. Like what we used to see when televisions were recorded on video. For some reason it's not as noticeable with the Fuji AF zoom lens, but it is there. I tried different settings in the camera menu to no avail. Then I just put a negative on my fluorescent light box and sure enough there it is. On the color head with halogen bulb there is no problem. I guess I'll have to digitize the 8X10s on the copy stand over a continuous light source or electronic flash. Sorry I don't have an example of the banding. I deleted them all but I can set it up to occur again. I'd like to know if this problem is unique to Fuji sensors or if it has been encountered with other types as well.

Has anyone else experienced this? I don't think LEDs are the answer unless running off a battery or a very well regulated DC supply.

Attachment 210525

Fluorescent lights are known to often show banding. If I am understanding your issue correctly, I would make sure "silent shutter" is turned off, and then vary your shutter speed in slight increments to see if the banding goes away. If not, a tungsten bulb or LED panel is probably the answer. I use an LED panel that plugs into a USB port or charger.

I tried both mechanical and electronic shutter separately to no avail. I can't choose long shutter speeds in the cold light enlarger because the source is so bright. Adding neutral density filtration to either the enlarger or the copy lens might be an answer. I tried exposing on a light box with LEDs running on AC and the banding was quite strong. LEDs can be strobed, that's how remote controllers work. Direct replacement LED tubes are flickering at at 50 or 60 ~, just like the fluorescent tubes they replaced. Not only that, they put out a lot of RFI you can hear on an AM radio, something the fluorescent tubes did not do. I have six four foot LED replacements in my lab. One benefit is that when turned off, they don't have an after glow like florescents and it's safe to handle films immediately. I once had an Aristo 12X12 cold light head with a factory dimmer power supply. When turned down, it flickered like crazy. I never used it that way, but of course it wouldn't affect print making and probably not long exposures with a digital copy camera.

The reason is that the fluorescent tubes are usually only running at 60 cycles/'flickers' per second.

To copy from a light source as you ar trying you need to get a HIGH SPEED Light source/table. This is an example of a good one for reproduction or copying of Negatives and transparencies:

Just Normlicht 10 x 20" Smart Light 5000 Transparency Viewer

With this you will not get the banding.
Rod

The reason for the issue has already been explained. As you mention, a longer exposure with ND filters may integrate enough to reduce it significantly assuming the flickering is a “zero mean” random variable.

Before investing in that you could take many shots of the same and average in photoshop. That will tell you how long the exposure may need to be (what filter is needed) and how well it would work, before you invest further in that solution.

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Originally Posted by Neal Chaves

I tried exposing on a light box with LEDs running on AC and the banding was quite strong. LEDs can be strobed, that's how remote controllers work. Direct replacement LED tubes are flickering at at 50 or 60 ~, just like the fluorescent tubes they replaced.

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Well, yes-- any light source using direct AC is going to flicker. Get a decent DC power supply, and run the LED's from that.

Or just get a decent LED lightbox.

I'll be back at work on the banding problem next week. Meanwhile, I am making a better mount for the camera to shoot up into the enlarger. I'll be looking at several approaches lighting for negatives and transparencies. What surprised me was discovering that the camera sensor is running at a certain frequency which must be close to 60~ or some multiple of it to strobe the LEDs and fluorescents running on AC.

You have the opposite problem. The camera is taking pictures fast enough that some elements are on, and some elements are off-- more accurately, the different elements have been on and off for differing amounts of time, so you see banding.

When doing traditional printing, this isn't a problem-- you're working in multiple seconds per exposure, so each element can switch on/off (or flicker, in the case of incandescent) repeatedly, but you get a continuous illumination over time.

LED's in particular, because of their very fast ramp up/down characteristics, can easily show a 60 cycle/second flicker.