Amateur Photographer & What Digital Camera: Red filter test

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numanoid
I'm 'Special'...

Reged: 27/01/2002
Posts: 10643
Loc: Co.Durham

Red filter test

#622326 - 05/03/2008 20:39

Here's something of note. I photographed this tree in black and white and the sky was a bit cloudy so i thought i'd see how it works with a red filter to increase contrast. First the pic without the filter
http://img.photobucket.com/albums/v11/Dawnrider/treesilhouertte01.jpg

And here with the R2 red filter,which can totally darken a deep blue sky. The difference is amazing,and its not just darker because the the camera automaticaly compensates.
http://img.photobucket.com/albums/v11/Dawnrider/treesilhouertte_plus_R2.jpg

--------------------

~Larry~
BSRIPN
http://www.members.lycos.co.uk/numanoid27/

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beejaybee
Marvin

Reged: 18/07/2007
Posts: 6274
Loc: Really Here In Name Only

Re: Red filter test

[Re: numanoid]
#622553 - 06/03/2008 08:59

Quote:

And here with the R2 red filter,which can totally darken a deep blue sky. The difference is amazing,and its not just darker because the the camera automaticaly compensates.

Not sure about that, when an image is dominated by one colour (especially one at the extreme end of the spectrum) the meter is likely to be flummoxed to some extent.

I've worked a lot with the B+W 091 filter and monochrome film (usually FP4) and find that the best way to get the exposure right is to use an external meter, set the camera to manual mode and overexpose by 3 stops (to allow for the filter factor of x8). The TTL meter on the OM-3 will usually show this as an overexposure of about one stop i.e. the camera light metering is more sensitive to extreme red than the film is.

This is even more the case with digital cameras with IR blocking filters - these start to kick in around the wavelength that the 091 begins to transmit, and a fair amount of exposure compensation is therefore likely to be required.

BTW the usual reason for a red filter is to darken blue sky with reference to white clouds - it's usually actually overkill with cumulus cloud (the hard fluffy kind - try orange or yellow instead) but works very well with cirrus.

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numanoid
I'm 'Special'...

Reged: 27/01/2002
Posts: 10643
Loc: Co.Durham

Re: Red filter test

[Re: beejaybee]
#622601 - 06/03/2008 10:43

Yea i did notice on some other pics that things look muddy yet there are strange highlights,and some conifer trees appear to glow palely(i expected them to be dark as they were in leaf and red filters darken green) . Its almost as if its picking up IR background.

--------------------

~Larry~
BSRIPN
http://www.members.lycos.co.uk/numanoid27/

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