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Judging exposure for blue sensitive film

 
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primus96



Joined: 13 Nov 2003
Posts: 211
Location: Yorkshire, United Kingdom

PostPosted: Sat Apr 29, 2017 5:25 pm    Post subject: Judging exposure for blue sensitive film Reply with quote

Has anyone here shot any amount of blue-sensitive fillm?
Compared to panchromatic stock grass is rendered as if it was under-exposed or actually dark blue. My blue motorcycle.... It looks as if it was vanilla yellow.
My helmet that was also in shot is monochrome and looks the same as rendered on normal stock.
I was using Eastman 5302 Release Positive in a Nikon
From that experience it suggests that it may be better to avoid blue sensitive X-ray film unless it was very cheap.
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Henry



Joined: 09 May 2001
Posts: 1553
Location: Allentown, Pennsylvania

PostPosted: Tue May 02, 2017 3:30 pm    Post subject: Reply with quote

To answer your question, no, I haven't. Read on....

If you google "blue sensitive black and white film," you'll get lots of hits. I found this one to be particularly informative: http://www.cosmeticsandskin.com/cdc/panchromatic.php

Although you asked about film, filters work in similar fashion. The basic thing to remember is that a filter passes its own color and blocks others. A blue filter passes blue light and blocks red and green. With panchromatic film, a blue filter (blocks red and green) will strongly emphasize sky in the negative, darkening those those areas on the film. So, too, with blue sensitive film. Dark areas in the film hold back light from the printing paper, and therefore the corresponding area of the positive looks pale. This fact explains why blue-sensitive film records a blue sky as dark in the film, and consequently light in the print---thus the washed-out sky, and consequent lack of contrast between sky and clouds, that one sees in so many 19th century prints (and in the photo in the article linked above): early film emulsions were overly blue-sensitive, darkening sky in the negative and lightening sky in the print. Conversely, a filter or film that blocks a particular wave length (i.e., color) will render that area light in the negative and dark in the print. This explains the use of a yellow (passes red + green, blocks blue) or a red (blocks blue and green) filter to darken blue skies in the print.

Keep in mind, too, that in photography we are speaking of the primary colors of light, which are blue, red, green (red + blue = magenta, red + green = yellow, green + blue = cyan). In pigments, the primaries are yellow, red, and blue (blue + yellow = green, etc.)

Are you confused yet? (I am.... ). I'd stick with panchromatic film, if I were you, and even here so-called "panchromatic" film doesn't accurately render the color relationships in black, white, and grays as the eye sees them; that's why there are so many filters, such as, for example, the yellow contrast filters no. 8 (K2) and no. 15 (G) used to emphasize the blue sky.

(While we're at it, let's pause to honor the memory of William Henry Fox Talbot, originator of the negative-positive concept in photography, and its first practitioner.)
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primus96



Joined: 13 Nov 2003
Posts: 211
Location: Yorkshire, United Kingdom

PostPosted: Wed May 03, 2017 6:23 am    Post subject: Re: Judging Exposure for blue sensitive film Reply with quote

I should have stuck my strongest blue filter in front of the meter cell.
The Maco GPF4 I have is orthochromatic & the only X-ray film I got is 4x4" Kodak green sensitive.
WHFT had to build the camera and lens & coat his own 'film', which I assume was blue sensitive. I would like to say "thank-you very, much" to that gentleman.
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Henry



Joined: 09 May 2001
Posts: 1553
Location: Allentown, Pennsylvania

PostPosted: Wed May 03, 2017 1:48 pm    Post subject: Reply with quote

Ditto that. On a trip to the Mother Country in 2004, I made a special point of visiting Lacock Abbey and seeking out the oriel window, the subject of the world's very first photographic negative (1835). How many billions (trillions?) of images have been recorded ever since that time? It boggles the mind....
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William Hallett



Joined: 07 Jan 2012
Posts: 46

PostPosted: Wed May 03, 2017 3:18 pm    Post subject: Reply with quote

I've shot a few sheets of Ilford's Ortho film, which probably has a wider spectral range than 19th century emulsions but is nonetheless mainly sensitive to the blue/green end of the spectrum. Ilford's instructions give different speeds depending on the light source: 80 ISO for daylight, 40 ISO for tungsten light. This makes sense, as the tungsten light has much more of the red end of the spectrum in it than does daylight, hence effectively exposes the film less.
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Billy Canuck



Joined: 04 Apr 2006
Posts: 161
Location: Calgary AB Canada

PostPosted: Wed May 03, 2017 9:50 pm    Post subject: Reply with quote

I'm old enough to remember shooting Verichrome as a boy when it was still an orthochromatic film. On a sunny day blue skies would come out dead white and portraits had extraordinarily dark lips. Verichrome Pan came out shortly after. This was a great film, wish it were still around!
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Henry



Joined: 09 May 2001
Posts: 1553
Location: Allentown, Pennsylvania

PostPosted: Thu May 04, 2017 12:51 am    Post subject: Reply with quote

Yes indeed! I would also like Panatomic-X and Plus-X back, too. Fat chance
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