Re: DSLR - background field colour cast...

On Fri, 29 Apr 2005 19:58:55 -0700, Gary G <see.signature@bottom>
wrote:

>On 29 Apr 2005 05:52:45 -0700, "justbeats" <steve_beats@xxxxxxxxxxx>
>wrote:
>
>>
>>My brightfield images always have a pale "salmon coloured" cast to the
>>background. I generally run the lamp at around 6-7V, but the issue
>>persists at 12V too - so I don't think it can be a colour temperature
>>thing(?). Visually, the background looks perfectly white to me.
>>
>>I'm projecting the image directly onto the 10D's CMOS sensor and
>>thought maybe IR was the problem but adding an IR blocking filter just
>>before the condenser made no difference!?
>>
>>Is this just a common issue that's always fixed by later colour and
>>white balance tweaks (which seem to work just fine), or am I missing
>>something at the capture stage?
>>
>> Cheers
>> Beats
>>
>>PS. Scope is a Zeiss ICM 405 inverted with an EOS 10D attached to the
>>front photoport. Light is 12V/100W halogen.
>
>Check out Extensis Intellihance. This is a plug-in for Photoshop. It
>will allow simple or aggressive cast removal.
>
>

The reason the image is yellow is due to different color temperature.
Your camera is probably set for daylight (5000K-6600K) while halogen
bulbs are about 2950K. Dedicated microphoto systems fix this by
changing the color temp of the light source at the source. Oly uses
an LBD filter (others do the same--they are a blue filter) just past
the lamp house or above the lower projecting field lens. This brings
it much closed to daylight. If your camera supports variable color
temp settings, try setting it to 2900K, 3200K, thereabouts.
Otherwise, try Incandescent if it has that option.

Gary Gaugler, Ph.D.
Microtechnics, Inc.
Granite Bay, CA 95746
916.791.8191
gary@microtechnics dot com
.

Relevant Pages

  • Re: I have an idea for a stable light-source, but is there a market for it?
    ... You may want to look into biothech instruments for light source ... way to stabilize a filament light-source. ... I've spent a little time doing market research, ... power supply and lamp control; they are: ...
    (sci.optics)
  • Re: Halogen or fullspectrum? HELP!
    ... > enough to light up one person just like on a mini-stage, but my lamp ... A kilowatt light produces heat. ... You absolutely must cool the IR filter. ... Your best bet would be the cold mirror. ...
    (sci.chem)
  • Re: Tentative MAG Update
    ... a chance at DSM. ... but very few chances of a permanent light source (the only ... most bones files don't include a magic lamp. ... they never had a chance to use their breath attacks.) ...
    (rec.games.roguelike.nethack)
  • Re: A Wizards Choice
    ... lamp as a light source, but spellbooks have been woefully hard to find. ... My question is, should I bless the lamp and use my wish, or should I ... It also grants TC and warning but a wiz ...
    (rec.games.roguelike.nethack)
  • Re: Projection TV Follow-Up
    ... Granted, it is probably has a short-arc lamp and not a filament type, ... It has one light source, projected onto a chip that has millions of microscopic mirrors, which pop up at the correct time, thus sending the light packet to the optical lens and on towards the screen. ... The correct time is determined by when a color wheel is letting through *only* the color that is to be seen in that portion of the screen. ...
    (rec.aviation.piloting)