View Full Version : Is there such thing as film flare?

chris jordan
23-May-2005, 20:02
Hi guys, I've been wondering something, which if I ask it will put me in the category of ultra-dweeb-nerd, but I'm probably in that category already so here goes. I've noticed that when I scan my film at very high resolution and zoom way into the scan, I frequently see places where bright highlights are fuzzed over into neighboring dark areas slightly. In an extreme example, in an image of sunlight shining down through trees, some of the leaves are partially blown out by a flare effect from the sunlight. I notice a much more subtle version of this effect in many of my photos, where bright areas fuzz over into dark areas, creating a kind of pale halo in what should be a deep shadow. These are very small areas, only visible at huge magnification, but I make giant prints so it actually does end up mattering. Consequently I spend lots of time carefully editing these halos out in Photoshop so they don't show up in my prints.

What I'm wondering is whether this is some artifact of the imperfect optical process (I'm using the best quality modern equipment available), or whether maybe the film itself is reflecting the brighter light horizontally outward inside the film base, exposing the nearby areas. I have heard that some printing papers do this (it is called "piping") but I don't know if film does it. Does anyone happen to have any more-than-speculative knowledge about this nerdy subject?


Melchi M. Michel
23-May-2005, 20:33

I suspect this is plain old lens flare. I see no reason to expect that optics in scanners be any less prone to lens flare than camera lenses. If your slides are really high contrast ( and I'm assuming that you're scanning slides because they typically deliver higher dmin/dmax contrast ratios) then you should expect a little bit of flare, as you would in a real-world high-contrast scene.

Melchi M. Michel
23-May-2005, 20:36
by the way, I really dig your work!

Oren Grad
23-May-2005, 20:58
I don't know how vulnerable current color transparency films are to halation effects, but I certainly have plenty of B&W negatives with them. And every LF lens I own, including my best modern glass - Apo-Sironar-N/S and Apo-Symmar - has at least some vulnerability to flare under extreme conditions. So that's two potential sources.

Have you examined your film directly under high magnification to see whether the effect is independent of the scanner?

Jorge Gasteazoro
23-May-2005, 21:15
If I understand correctly what you described, it is called infectious development, where parts of the film that have received excessive exposure bleed into the dark parts.

Since you cannot adjust color film development you will have to live with this.

Here is an example, the window light bled into the dark parts of the window frame. I did this on purpose, but I could have avoided this by giving more exposure and developing even less than what I did.


23-May-2005, 21:28
I think the answer is yes, there is such thing as film flare, and it's called halation.
However, as others have said, lens flare is usually greater. And modern films (partly because of anti-halations dies and partly because the emulsions are so thin) don't exhibit nearly as much of this as old ones.

I haven't heard of infectious development (sounds like a horrible skin condition), but if Jorge is getting a phenomenon like this that responds to development, then it could be yet another factor.

If you want to firmly entrench yourself in the ultra-dweeb-nerd category, you could test it by contact printing some knd of high contrast test target onto a piece of your film. A film or glass plate test target would work great; so would making a photogram of something like a razor blade.

Jorge Gasteazoro
23-May-2005, 21:44
Paul, you might also have heard it call irradiation (which in fact it is a more accurate name.) In the case of halation we have light rays going through the film, bouncing off the back of the holder and due to the difraction cause a halo bleeding into the dark parts. This was a common ocurrence with older films but rarely happens .

Conversely, irradiation is unavoidable when excessive exposure occurs. Film is a turbid medium and as such it scatters light, in the case of excessive exposure such as the example given by Jordan or my example, some of the light that exposes the light parts scatters into the parts where there is no exposure. This can be controlled with development to an extent, but in some cases it is down right impossible or in the case of color film unavoidable since you cannot reduce development.

Ralph Barker
23-May-2005, 21:48
Gee, I always thought that things that were irradiated couldn't reproduce. ;-)

Jorge Gasteazoro
23-May-2005, 21:54
You are absolutly right Ralph, this is why film cant reproduce. Would be nice though, all we would need to do is buy two sheets and let them go at it... :-D

23-May-2005, 23:18
that makes sense; i never heard the distinction made between irradiation and halation. i knew about the phenomenon of the emulsion scattering light, but i just lumped those ideas together.

Graeme Hird
24-May-2005, 01:53

Have you absolutely ruled out your scanner in this? Are the artifacts on the film under a microscope?

The reason I ask is that I have found a similar effect when the exposure through the scanner is too high and the sensor "bleeds" the highlights into the shadows.


Keith Laban
24-May-2005, 02:43

I often see this effect, particularly when shooting the tree canopy in woodland. Tiny areas of what are inevitably grossly over exposed sky 'bleeding' into the surrounding leaves and branches. I'm afraid this is inevitable; thank God for Photoshop ;-)

Keith Laban
24-May-2005, 16:12
I omitted to add that I see this on the original transparency, not just the scan.