[rollei_list] Re: Slide film is still alive
- From: "John Wild" <JWild@xxxxxxxxxxxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Fri, 22 Feb 2008 17:47:15 -0000
Lance,
Under certain conditions there can be a slight colour cast, e.g.
photographs in the shade at midday in summer may have a slight blue
cast; similarly in the mountains and with snow. The light from the deep
blue sky is less absorbed by the atmosphere when the sun is directly
above and is very blue, giving rise to this blue cast. Towards the
beginning and end of the day the light is warmer, as more of the blue
light is absorbed by the greater distance the sunlight travels through
the atmosphere (the sun being lower in the sky), giving an red/orange
cast.
When using colour negative film, most casts are filtered out when the
print is made (professional processing labs have this down to a fine
art); fluorescent lights give a greenish cast and this is more difficult
to remove. Even daylight film, recorded under incandescent light can be
almost corrected to give all but a warm glow. If you take a lovely
sunset on negative film, often the lab will correct this to give a
'white' sky and it will be nothing like the original scene. Very
disappointing. They should know that the photographer wanted to record
the vibrant red and orange glow in the sky. ;-)
However, transparency film is the end result and so whatever the colour
temperature is, this is recorded on the film. If severely different
from, say daylight film's recommended 5700/6000K, it will have a cast.
Above this figure gives a blue cast and below, a reddish cast.
Incandescent lights give a orange/yellow cast, having a 'warmer' but
lower numbered temperature. In this situation you require a blue filter
when using daylight film (I cannot remember the Kodak Wratten filter
numbers off hand). The larger the 'K' (Kelvin) number, the 'cooler' the
temperature. A clear blue sky can be upwards of 40,000K and a candle
just a few hundred K. The reason why correction from the blue sky is not
required for midday sunlit photographs is because the proportion of
warmer sunlight is far greater than the influence from the colder blue
sky. In the shade there is no direct sunlight, the light just coming
from the cooler blue sky. Similarly when using electronic flash indoors.
The flash light will have more influence than the incandescent light
bulbs, so no correction will be necessary (unless a time exposure is
used which will reverse the proportions of lighting influence).
=20
With transparency film it's WYSIWYG. So, one advantage is that the
lovely sunset is recorded as a red sky, just what you want. However, the
blue cast in shade at midday or in the mountains can give a somewhat
cool feel but this can be corrected with a rose tinted 'warm-up' filter.
Professional photographers may be required to photograph products with
100% colour accuracy, so will use a colour temperature meter and be able
to use the correct filtration to adjust the lighting to accurately match
the film.
For 'normal' photography with daylight transparency film a 'warm-up'
filter is really all that is needed unless you are indoors with
incandescent lighting. If you want to record accurate nature colours for
instance, then more accurate filtration will be required. Reference to
charts which are based on the sun's elevation (time of day) and
declination (according to time of year) and height and source of light
have been outmoded by the colour temperature meter. I saw a Gossen
meter on Ebay a couple of years ago and thought it would be nice to
have. Expecting it to go for a silly price I only looked at it again
once the auction had finished. It sold for about $60. A bargain sorely
missed. I don't suppose I would have ever used it though but it would
have been a nice ornament. ;-)
Best wishes
John
-----Original Message-----
From: rollei_list-bounce@xxxxxxxxxxxxx
[mailto:rollei_list-bounce@xxxxxxxxxxxxx] On Behalf Of
Choiliefan@xxxxxxx
Sent: 22 February 2008 14:46
To: rollei_list@xxxxxxxxxxxxx
Subject: [rollei_list] Re: Slide film is still alive
=20
Carlos,
I've been shooting slide film lately and have scanned a few images
successfully but not posted anything Rollei related yet.
I'm still confused about filtration in shade with slide vs positive film
and have another experimental roll to drop off today.
So far Ebay has been a great way to buy 120 and 220 film for a fraction
of the cost of new stock and the colors are vivid even on the badly
outdated stuff.
Health, Peace
Lance
Selma, NC 27576
~~~~~~~~~~~~~~~~
=20
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