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Re: [OM] B&W filters on digital [was Non Bokeh 50mm F1.4 pictures]

Subject: Re: [OM] B&W filters on digital [was Non Bokeh 50mm F1.4 pictures]
From: "C.H.Ling" <ch_photo@xxxxxxxxxxxxx>
Date: Thu, 27 May 2010 10:16:03 +0800
Thanks for the experiment, I'm interested to see the result. More on the 
pixel quality after red filter, red channel is the weakest one on digital. 
Lost of details is rather obvious after process with digital red filter, it 
would be nice to know if a real lens filter will do better.

As for the post editor, I think most would be ok as the processing mainly 
deal with RGB level adjustment, no interpolation involved.

Linear curve adjustment to make all files equal in contrast may not 
necessary, to me matching the mid-tone level by +/- compensation on RAW 
converter is fine but it is up to you.

Using the camera RAW converter is a good idea. The main problem is you can't 
use the same level of NR to all, this will have great influence on the final 
result. (The red channel on non NR files from Canyon is terrible.) On the 
other hand the NR level may not be the same even you use the same RAW 
converter for different camera files.

C.H.Ling

----- Original Message ----- 
From: "Ken Norton" <ken@xxxxxxxxxxx>


> At lunchtime I went through the local taco takeout (trots on the run?
> Get your runs at the border? Chuck-a-Chimi?) and headed over to a park
> to do a little B&W testing.
>
> I tested three cameras: Olympus E-1, Minolta A1 and the Panasonic L1.
> You think I like the number one?
>
> On the E-1 and L1 the 50mm F1.4 was mounted and the aperture set to
> F8. With an ISO of 100, the standard exposure for the sunny day, with
> occasional cumulus clouds was F8 at 1/400. So I did a single
> unfiltered shot at F8 and 1/400. Then I took exactly the same picture
> with a green, yellow, orange and red filter at 1/400. Each filter
> image was also taken at 1/200 and additionally the red taken at 1/100.
> I repeated the test on the A1, but had to set its lens to F10 to
> compensate for the true ISO 160 sensitivity of the sensor.
>
> So, now I have a set of images from three cameras with one straight
> image, and two (or three) images with each of the filters.
>
> The end goal here is to come up with a final image of each color
> filter setting. One derived through post-processing (color filtering
> in the editor) and the other through converting the lens-filtered
> image and monochroming it.
>
> I'll get a round tuit sometime this evening, but do you have any
> preferences as to how I go about this test? I will be doing all
> editing in PWP as it supports 16-bit and has one of the better
> color-to-monochrome converters around.
>
> I'm thinking that I'll RAW convert the files straight with no color or
> monochroming (which will result in green, yellow, orange and red
> colored files) and save them as 16-bit tiffs. The tiff files would
> then be opened in PWP and converted to monochrome. After converting to
> monochrome, a linear curve adjustment will be applied to top-and-tail
> the histogram so all images will be identical in contrast. Each file
> will be resized to 800 width, but a detail section will be cropped to
> provide a pixel-peeping oddessy for those wanting that. Files will be
> converted to 8-bit and saved at 95% (2.3:1 or so compression) jpeg to
> minimize jpeg artifacting. The full-color image will be converted to
> monochrome using each of the same color filter settings (green,
> yellow, orange, red) and then the same curves adjustments applied.
>
> I believe that the above procedure eliminates variabilities in RAW
> converters and places all the onus on the editor, which in this case
> will be used to create as close to identical files (for each color) as
> possible. If I do the same procedure and adjust contrast to 0%-100%
> the results should give us a good baseline.
>
> To reduce variabilities in raw converters I'm thinking of converting
> all of them with the DCRAW engine in PWP, but that does result in
> other artifacts, so I'd prefer to use the converter which is optimized
> for each of the cameras. ACR also artifacts these files, so I'm not
> comfortable using that across the boards either.
>
> Moose?  CH?  Thoughts or recommendations?
>
> AG

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