Black and White - DPChallenge Forums

02/02/2004 02:05:38 PM · #26

Originally posted by soup:

yeah i have had better luck results with the channel mixer myself, put keep eyes open for other methods.. i didnt know that some channels are noisier than others, thanks for pointing that out.

and seems to be right on, as i tend to see the most noise in the skies... which would be a blue channel obviously - so when shooting blue skies - noise would seem hard to avoid ( and a frustrating limitation - i try to stay away from neat image if possible ) - white balance would mees up the blues in all aspects of the shot..

thanks for the reply.

A good approach to addressing that noise is to:

Switch to LAB mode (non destructive/ reversable process)

Apply gaussian blur to the A & B channels. Leave the L channel alone.

Convert back to RGB.

This works well because you apply the blurring to the colour channels only. Colour, unlike tone has a much lower spatial frequency so you can blur it heavily with little or not impact on the actual image. However, you blur away all the channel specific noise. As you leave the L (lightness - or tone) channel unchanged, you keep all the sharpness and lose a lot of the noise

02/02/2004 02:57:38 PM · #27

will do tonight on the same camels hump image i have posted - there is noise in the sky for sure, although i personally dont think its too destructive. in my film days i would get noise ( grain ) in the same situations, but that tended to be more subtle, and finer for sure.

triX 400.. could be the culprit as well ;)

EDIT: then i am assuming use channels or some other grey scale conversion technique - meaning above only adresses the noise itself... correct?

Originally posted by Gordon:

thanks

Message edited by author 2004-02-02 14:59:03.

02/02/2004 03:56:01 PM · #28

Originally posted by soup:

EDIT: then i am assuming use channels or some other grey scale conversion technique - meaning above only adresses the noise itself... correct?

thanks

Yup, this is just another way of reducing channel noise, without messing up the actual colour image.

You can also try just blurring the blue channel alone as well, as a lot of the noise resides there, as people have mentioned.

02/02/2004 04:16:52 PM · #29

wonder if thats why the new sony is spliting sensor up into 4 colors. EDIT: then again i suppose its still an RGB image in the end...

would seem in a higher end'ish camera the noise issues would be pretty non existent - or at least consistantly low at the R, G, B levels equally, rather than a couple good channels and a bad one. i mean its when i convert to BW that i see it most - but its there in the color versions as well.

basically i have gotten to know my new camera well, having been a few years since i used a decent one, and adpating to the rich feature set ( i shot manual camera / film in the past ), and am getting properly exposed, sharp, colorful shots. but if there's blue sky - there's noise no matter what i do...

thanks for all the input

EDIT cont; i would try RAW, but i shoot alot of photos, and file storage is becoming an issue. and not 100% it would make a difference in the noise.

Message edited by author 2004-02-02 16:20:04.

02/02/2004 06:44:13 PM · #30

so i tested the grain reduction method. works pretty good.

heres a comparison of the image at 100% using just the channel mixer, and the other both lab mode, and channel mixer. pretty astounding.
and the whole image using the second technique. the other BW versions are in my portfolio under vermont.

thanks for the great tip ;}

Originally posted by Gordon:

Originally posted by Gordon:

--------------------------------------------------------------------------------
A good approach to addressing that noise is to:

Switch to LAB mode (non destructive/ reversable process)

Apply gaussian blur to the A & B channels. Leave the L channel alone.

Convert back to RGB.

This works well because you apply the blurring to the colour channels only. Colour, unlike tone has a much lower spatial frequency so you can blur it heavily with little or not impact on the actual image. However, you blur away all the channel specific noise. As you leave the L (lightness - or tone) channel unchanged, you keep all the sharpness and lose a lot of the noise

dwoolridge

02/03/2004 05:50:06 AM · #31

Originally posted by Gordon:

Switch to LAB mode (non destructive/ reversable process)

Apply gaussian blur to the A & B channels. Leave the L channel alone.

Convert back to RGB.

Well, I'd be careful using LAB mode as colour information can be lost through quantization errors, particularly if you work with 8-bit in sRGB. To be safe, use 16-bit in a wide(r) color space. Note that multiple rgb->lab->rgb conversions (in 8-bit sRGB especially) are worse than a single conversion (although each additional conversion's loss is smaller than the previous one).

Bruce Lindbloom has more information and though his test case image demonstrates the problem readily, my experience is that it's an issue even in photographic images.

02/03/2004 08:44:56 AM · #32

Originally posted by dwoolridge:

Originally posted by Gordon:
Switch to LAB mode (non destructive/ reversable process)

Apply gaussian blur to the A & B channels. Leave the L channel alone.

Convert back to RGB.

Well, I'd be careful using LAB mode as colour information can be lost through quantization errors, particularly if you work with 8-bit in sRGB. To be safe, use 16-bit in a wide(r) color space. Note that multiple rgb->lab->rgb conversions (in 8-bit sRGB especially) are worse than a single conversion (although each additional conversion's loss is smaller than the previous one).

Bruce Lindbloom has more information and though his test case image demonstrates the problem readily, my experience is that it's an issue even in photographic images.

Guess that's why I don't see problems - I don't work in 8 bit mode at all now appart from final output, and I don't work in sRGB, again appart from converting to that space for final output.

There are trade-offs for using larger colour spaces like AdobeRGB though as well - mainly larger 'steps' between each point in the colour space, but for anything I'm considering printing I work in a 16 bit, and wide gamut space.

dwoolridge

02/03/2004 09:16:36 AM · #33

Originally posted by Gordon:

Guess that's why I don't see problems - I don't work in 8 bit mode at all now appart from final output, and I don't work in sRGB, again appart from converting to that space for final output.

Yeah, I assume as much. My comment was mostly targeted at anyone else who might be tempted to try this in srgb/8.

Originally posted by Gordon:

There are trade-offs for using larger colour spaces like AdobeRGB though as well - mainly larger 'steps' between each point in the colour space, but for anything I'm considering printing I work in a 16 bit, and wide gamut space.

Which space are you using? Although my whitepoint is d65 right now, I'm thinking of switching to D50 so I can use something like Best RGB, Beta RGB, or Wide Gamut RGB. My lack of motivation here is that I can achieve most of my desired results during RAW conversion; B&W is one of the big areas editing is necessary.

02/03/2004 10:22:39 AM · #34

I use the CaptureOne Generic D60 profile, then usually work in that or AdobeRGB.

Monitor is calibrated with a Colorvision Photocal spyder. Most of the output is either on wide gamut dye based inkjets or whatever the large format ezprints printers are. I'm beginning to be less satisfied with ezprints and thinking of switching ot west coast imaging for larger prints. Price is a bit higher but they seem to care more about colour managed output.

02/03/2004 10:22:54 AM · #35

well, i don't see myself using that techinque for anything but noise reduction in a BW conversion, and it seems that there are much lossier processes to get to BW on the PC.

i have been interested to see all these recently posted ways to get BW, and trying combinations of them used together. i am somewhat new to digital photo editing, and have been frustrated with the BW results in a lot of cases. i only shot BW film when i was younger, and would like to get back into to BW - if there is a consistent, and quality set of steps to achieve consistent good results. it surprises me adobe hasn't built in a decent BW conversion filter yet.

02/03/2004 10:30:08 AM · #36

Originally posted by soup:

i only shot BW film when i was younger, and would like to get back into to BW - if there is a consistent, and quality set of steps to achieve consistent good results.

There are two main barriers to decent digital B&W

1/ editing space

2/ output tonal range

and one thing really causing the lack of progress

3/ lack of demand

Right now, my images all end up going through the 'greyscale' reduction stage before I get to duotone the output. This means that there are only ever going to be 256 grey levels in the image - which is pretty bad and makes it next to impossible to get something that can look as good as film, through digital editing approaches. Adobe could fix this in future version of photoshop, to at least let greyscale images have 16 bit levels or 65,536 tones which would be a huge improvement.

Then it comes to print the images. Mostly prints get printed on inkjet printers. Typically with 3-6 colour and one or two black inks. This means you are dithering colours to get decent black and grey shades. Alternatives, like the pizeography technique (replace the inks with a 4 grey shade cartridge and dedicate the printer to B&W) exist - but you still have the editing challenge.

Then there is the lack of demand - not many people are pushing for this, there certainly isn't a huge market for it. Many are happy with the results of doing a desaturate or image-greyscale and not caring about the lack of dynamic range and colour casts in final prints.

I'm open to any and all suggestions on ways to get better B&Ws - I'd love to get there digitally some day or else I'm going to go and buy some B&W film for my camera...

02/03/2004 11:18:30 AM · #37

its the price of the BW film - decent film anyway - and then the processing of it. even when i had my darkroom set up - the cost of the chems, and paper, and water, and disposal of shot chems was/is too much.

i didn't actually think much about the digital processing, and the digital BW process at all when i got a digital camara. the kodak we bought on a whim for a vacation, and just didnt have the verstility i was used to. now that i can control my camera i started yearning BW again. i have a hard time thinking there is no demand for BW digital photos...

the editing space is something i am not familiar with at all... whatever PS defaults at is what i am using, i guess. imagine its 16bit.
been staying away from duotone because of the grayscale conversion...
i would think there is a way to get duotone -w/o going to grayscale.
but i dont know the technicalities of what the duotone is exactly doing.
i would think layering, blending, and curves would be able to achieve similar results..

02/03/2004 11:21:45 AM · #38

Originally posted by soup:

i have a hard time thinking there is no demand for BW digital photos...

There isn't commercially significant demand at least for comapnies like Epson. Niche approaches have appeared but for the mass market, Image-> desaturate is more than acceptable. The majority of users are pretty happy to put up with crappy results (otherwise 1 hour photo places wouldnt do so well) convenience easily supplants quality for consumer printing, digital or film.