Red Window

[cliveh]

Why do so many film cameras have a red window at the back to read the film number when the film is panchromatic? Would not a dark green window make better sense?

[MattKing]

Why do so many film cameras have a red window at the back to read the film number when the film is panchromatic? Would not a dark green window make better sense?

Red windows were initially used with orthochromatic film.

I would guess that when panchromatic film became common, the windows stayed red because of tradition.

The colours of the film backing numbers may also have been designed with red windows in mind.

I'm not sure that green windows would be any better - panchromatic film is just as sensitive to green as it is to red.

[steven_e007]

I've seen green and a few cameras had both green and red windows. Seems a bit pointless really - any light leakage inside the camera would fog a modern film.

[railwayman3]

The thickness of the backing paper prevents any problems, but best to keep the window covered and to avoid bright sunlight when winding on the film.

[Clay2]

Yes, I have seen green windows as well as red.

Best regards,

/Clay

[Photo Engineer]

Many later windows had little covers that prevented light leaks and that were only to be opened during film advance.

However, the other side of the story is that roll films had a heavy black paper backing that prevented light leaks. Of course, this became useless when film speeds passed about ISO 100.

PE

[paul ron]

And pointless when 220 hit the streets.. no backing paper after the first frame up to next to last frame or so.

[Photo Engineer]

Oh yeah, but you forgot that 220 cameras had no windows AFAIK.

PE

[jun]

Many later windows had little covers that prevented light leaks and that were only to be opened during film advance.

However, the other side of the story is that roll films had a heavy black paper backing that prevented light leaks. Of course, this became useless when film speeds passed about ISO 100.

PE

I frequently use Portra 800 (120) for my camera, made in 1954 (Bessa II with an incredible optics), which has a ruby window and a cover.
If you properly use it (close the cover within about 10 second or less after winding) I never had any problem even under direct sun light hitting the ruby window directly.
However, if I forget to close the cover under bright sunlight (say 3 hours or so), the film get exposed from the back of the film.
I see the exposed round spot just the size of ruby window on the film.
This means that the backing paper did not fully stop the light.

But I can't blame the film for this, this is just the wrong way to use the camera (leave the cover open esp. with the high speed film).
However when I shoot in the studio, I frequently just leave the cover open, so I can advance the film quickly and I know the low level of light will never fog the film.

Note that I did a proper modification to prevent light leaks (well, some of those old cameras are not light tight compared to the today's film cameras, in those days ASA 50 was standard, for color it was about ASA 10).
You should notice that for some old camera like this, opening the cover will not only illuminate the back of the film, but also the light can seep into the camera, resulting to expose the film not only from the back of the film.
My simple modification will prevent that, but you can't avoid hitting the light to the backing paper, unless you can see the numbers even you close the cover!

[Ian Grant]

Surprisingly some new cameras have no filter at all just a slider to cover the aperture. However they do have better pressure plates and light sealing around the window area inside the camera to prevent fogging. I've not had an issue and I mainly use 400 EI film in my 617 camera in Turkey where exposures are typically close the maxinum a meter will read, so I regularly shoot hand held 1/125 or even 1/250th @ f22

Should add that I've had no problems with backing papers from Kodak (TMY), Ilford (Delta 400 & HP5) or Foma (Fomapan 200) with the 617, however I have had problems seeing the numbers through the red filter on a pre WWII Inkonta - almost impossible.

Ian