As far as Canon is concerned the raw files contain raw sensor data as
well a lot of other info... Here is a link:
http://lclevy.free.fr/cr2/
Cheers Mark
Chris Tully wrote:
> Michelle,
>
> Not to be to commercial here but the kind of question you are asking
> here is trivial to answer in most image analysis programs without
> dropping down to the individual pixel values. Since you are using a
> single chip color camera keep in mind that some fraction of the pixels
> in each channel is extrapolated from its neighbors (For a Bayer
> pattern chip, 75% of the red and blue and 50% or the green pixels are
> extrapolated from their neighbors!). Assuming that you are talking
> about "consumer" type digital cameras, I am not as familiar with the
> chips and filter patterns that they use. Please note that on all the
> "consumer" grade digital cameras I have used, the "raw" format simply
> means an uncompressed image (usually in TIFF format). It does not
> mean the same thing as "raw" means coming from a "scientific" digital
> camera which usually means a gray scale image exactly as it was
> extracted from the chip before color processing (interpolation).
>
> Taking the software that I am most familiar with as an example
> (Image-Pro Plus) it is simple, even automatable, to select the range
> of Red, Green and Blue values of interest and ask the software for
> anything from the number of objects that meet that threshold to the
> total number of pixels that meet that threshold. If you have access
> to a copy of Image-Pro Plus, I would be happy to guide you through the
> analysis by phone or email.
>
> Chris Tully
> Microscopy and Image Analysis Expert
> [log in to unmask]
> 240-888-1021
> http://www.linkedin.com/in/christully
>
>
>
> On Fri, Feb 13, 2009 at 11:51 AM, Michelle Peckham
> <[log in to unmask]> wrote:
>
>> Thanks Jerry
>>
>> These are pictures taken with a digital camera (i.e. Nikon or Canon) in
>> 'raw' format. So your advice is great.
>>
>> This person wants to work out how much area is a particular shade/hue, so we
>> thought grey scale numbers in R,G and B channels would be the thing to go
>> for.
>>
>> So thanks for this.
>>
>> Michelle
>>
>>
>> On 13/02/2009 16:46, "Jerry Sedgewick" <[log in to unmask]> wrote:
>>
>>
>>> Is the file in the Raw format, such as those generated by Nikon and
>>> Canon consumer cameras? Or did you mean that the person was asking about
>>> the original (unaltered or raw) file?
>>>
>>> If it is the Nikon or Canon Raw format, then it was derived from a
>>> mosaic chip and colors will have to be assigned to each pixel through
>>> some kind of conversion "engine." Photoshop uses its own Adobe Camera
>>> Raw (ACR) engine in all the CS versions (as I recall). If the lighting
>>> for the study was consistent, and if the study occurred over more than
>>> one imaging session, then the settings in Adobe Camera Raw should be set
>>> similarly for the experiment, or the colors will have to be adjusted by
>>> using a reference standard (such as a neutral gray card, Macbeth color
>>> chart, or some consistent part of the specimen that is white or gray).
>>> If the colors are not assigned or adjusted to a standard, then the
>>> colors will be inconsistent from session to session.
>>>
>>> Canon and Nikon both have proprietary engines in which colors are
>>> generated at each x, y position. These can also be used, but make sure
>>> the gamma is set to 1, and, again, adjust colors based upon reference
>>> standards if images were taken at more than one session.
>>>
>>> Before opening the image in Photoshop, the Color Settings in the menu
>>> (Preferences>Color Settings) are changed from the RGB default setting
>>> (sRGB....). A "CIE 1931 D65" setting is chosen because this keeps the
>>> gamma at 1 (no alteration of post-ACR values). This color setting can be
>>> downloaded from quickphotoshop.com, but make sure to click on Book:
>>> Supplemental Info (not Download). Photoshop changes the gamma when using
>>> any of the other color settings. Gamma is a reference to the adjustment
>>> of pixel values destined for display on a computer monitor in which the
>>> Greek symbol gamma is the exponent in a math formula.
>>>
>>> Once in Photoshop, in the menu, under Windows, choose Channels
>>> (Windows>Channels). In the Channels palette, click on the upper right
>>> arrowhead and choose Split Channels from the drop down list. This will
>>> separate the red, green and blue channels for subsequent measurement.
>>>
>>> In the distant past, I believe I used Image J to generate pixel values
>>> at each x, y position, but maybe it was MatLab or MetaMorph. Maybe
>>> another person on the list can add that information.
>>>
>>> Cheers!
>>>
>>>
>>>
>>> Michelle Peckham wrote:
>>>
>>>> A little bit off the topic, but
>>>>
>>>> Someone here was asking me about analysing a ŚRAWą file for colour
>>>> information, and the simplest way to do what she wants would be to
>>>> extract the grey scale values out for the red, green and blue
>>>> channels, and analyse them in a spread sheet.
>>>>
>>>> Does anyone know how to do this?
>>>>
>>>> Michelle
>>>>
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