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Author Topic: Exposing for B&W digital?  (Read 4214 times)

lowep

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Exposing for B&W digital?
« on: July 15, 2016, 07:49:23 AM »

Should any different in camera exposure settings be used for capturing a RAW file intended for converting and processing as a B&W image than for a color image, or is it just the same as photographing color?

 
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razrblck

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Re: Exposing for B&W digital?
« Reply #1 on: July 15, 2016, 08:06:12 AM »

Same settings, except that I might be able to use higher ISO or push shadows a bit more since noise is less noticeable and color artifacts more or less disappear.
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graeme

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Re: Exposing for B&W digital?
« Reply #2 on: July 15, 2016, 10:01:25 AM »

Same settings, except that I might be able to use higher ISO or push shadows a bit more since noise is less noticeable and color artifacts more or less disappear.

That sounds reasonable
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BartvanderWolf

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Re: Exposing for B&W digital?
« Reply #4 on: July 16, 2016, 09:26:44 AM »

Should any different in camera exposure settings be used for capturing a RAW file intended for converting and processing as a B&W image than for a color image, or is it just the same as photographing color?

Hi,

In everyday practice, the same exposure will do.

When pixel peeping, technically there could be a (small) benefit from shooting through a somewhat magenta filter, to compensate for the denser Red/Blue filters in the Bayer CFA. That would require less boosting of those channels which would help to reduce noise a bit.

The amount of difference also depends on the final postprocessing, and how image colors are used to change the tonal balance.

Cheers,
Bart
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GrahamBy

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Re: Exposing for B&W digital?
« Reply #5 on: July 18, 2016, 12:15:54 PM »


When pixel peeping, technically there could be a (small) benefit from shooting through a somewhat magenta filter, to compensate for the denser Red/Blue filters in the Bayer CFA. That would require less boosting of those channels which would help to reduce noise a bit.

That's an interesting idea: but since in fact a filter doesn't increase red+blue but decreases green, wouldn't it actually be an issue of boosting G more, rather than R+B less? Unless you were determining exposure by G channel clipping... is that the point I'm missing?
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BartvanderWolf

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Re: Exposing for B&W digital?
« Reply #6 on: July 18, 2016, 12:21:11 PM »

That's an interesting idea: but since in fact a filter doesn't increase red+blue but decreases green, wouldn't it actually be an issue of boosting G more, rather than R+B less? Unless you were determining exposure by G channel clipping... is that the point I'm missing?

Hi,

Usually the Green color plane has the highest exposure (Raw DN), and Red/Blue much lower. The Magenta filter will indeed reduce green transmission, so one can increase overall exposure (for the underexposed R/B planes, and the now reduced G plane).

Cheers,
Bart
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SZRitter

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Re: Exposing for B&W digital?
« Reply #7 on: July 28, 2016, 10:41:11 AM »

Hi,

In everyday practice, the same exposure will do.

When pixel peeping, technically there could be a (small) benefit from shooting through a somewhat magenta filter, to compensate for the denser Red/Blue filters in the Bayer CFA. That would require less boosting of those channels which would help to reduce noise a bit.

The amount of difference also depends on the final postprocessing, and how image colors are used to change the tonal balance.

Cheers,
Bart

Curious, this is the first time I have heard this one. Kind of makes sense in theory, but have you tried it in a practical application and noticed any real difference?
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razrblck

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Re: Exposing for B&W digital?
« Reply #8 on: July 28, 2016, 11:24:16 AM »

I guess the general idea is to balance light between the red, green and blue filters, since there is twice green pixels as the others. For black and white this should pose no problem at all, but for color you will have issues with tones as RAW converters take for granted the additional green information witch will now be lacking.

I don't think you need a magenta filter that is too intense anyway. Also be aware of how many stops of light you lose with such a filter in front of the lens, as it can be anything between 2/3rds and 2 stops.
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scyth

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Re: Exposing for B&W digital?
« Reply #9 on: July 28, 2016, 11:58:12 AM »

Should any different in camera exposure settings be used for capturing a RAW file intended for converting and processing as a B&W image than for a color image, or is it just the same as photographing color?

you might want to pay attention, for example, to your raw converter/camera profile(s) of choice for this ... if you intend on doing B/W then sometimes the stronger noise is less visually bad or how converter handles transition from clipped (in raw, 3-2-1 channels) to non clipped areas is visually less distracting... so you in fact can then either underexpose more or overexpose more based on that vs when you think about doing color.
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scyth

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Re: Exposing for B&W digital?
« Reply #10 on: July 28, 2016, 12:00:41 PM »

I guess the general idea is to balance light between the red, green and blue filters, since there is twice green pixels as the others.
magenta filters are not about "green" sensels being twice more count wise - it is about the illumination spectrum + CFA spectral transmission giving more saturation to sensels behind "green" CFA filters... plus in a studio (or even outside in some cases) you can always gel the light
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Telecaster

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Re: Exposing for B&W digital?
« Reply #11 on: July 28, 2016, 04:29:17 PM »

Curious, this is the first time I have heard this one. Kind of makes sense in theory, but have you tried it in a practical application and noticed any real difference?

I did some of this awhile back with a mild magenta filter. In many situations it did pull down the green channel, giving a more spectrally balanced exposure. This let me ETTR more effectively when taking pics with b&w in mind. Nowadays I don't bother…current sensors have enough latitude that it's rarely even a minor issue (for me).

-Dave-
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BartvanderWolf

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Re: Exposing for B&W digital?
« Reply #12 on: July 29, 2016, 03:41:52 AM »

Curious, this is the first time I have heard this one. Kind of makes sense in theory, but have you tried it in a practical application and noticed any real difference?

Hi,

I'm not particularly into B/W photography, but in an odd case (depending on the spectral content of the scene, it would help (a bit). Whether it's worth the risk of optical image deterioration (dirt / veiling glare / optical imperfections) remains to be seen on a case by case situation.

Cheers,
Bart
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Guillermo Luijk

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Re: Exposing for B&W digital?
« Reply #13 on: August 07, 2016, 04:14:06 AM »

When pixel peeping, technically there could be a (small) benefit from shooting through a somewhat magenta filter, to compensate for the denser Red/Blue filters in the Bayer CFA. That would require less boosting of those channels which would help to reduce noise a bit.

Hi Bart, your idea is fine (in fact some people use it), when there is enough light to have a good exposure at base ISO. For instance it will produce cleaner shadows in well lit high contrast scenes. But if there is a lack of light (need to push ISO), it would have an overall negative impact on noise. In this situation the more photons you collect the better.

Aside from that, having channels with different sensitivity (i.e. G ending with higher levels in the RAW file) can have some advantage for B&W photography: while G can get clipped in the highlights, you can still 'recover' a nice grayscale gradient from the R and/or B channels there. The G channel will help you in having sufficiently noiseless shadows. Kind of inter-channel HDR that enhances DR for B&W, specially if some strategy is applied to weight more higher SNR channels on each image area.

That is one of the reasons why paradoxically I don't think monochrome sensors are the best option for B&W photography. When the Leica Monochrome has its highlights clipped, there is nothing to do there: pure white, zero information. This is much harder to happen on a Bayer sensor, where you need to severily overexpose to blow the three channels at the same time. Instead monochrome sensors are dramatically digital, right the opposite concept Leica represents. If I had that camera I would tend to underexpose a bit in order not to ruin the highlights, but this would reduce potential DR.

Another disadvantage of monochrome sensors is that you cannot apply software colour filters, which are very flexible and straightforward.

Back to the topic, in general exposing for B&W is less demanding than doing for colour. If you are lucky to have a mirrorless camera you can even previsualize in B&W.

Regards


www.guillermoluijk.com
« Last Edit: August 08, 2016, 10:04:35 AM by Guillermo Luijk »
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luxborealis

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Re: Exposing for B&W digital?
« Reply #14 on: August 14, 2016, 07:25:44 PM »

Should any different in camera exposure settings be used for capturing a RAW file intended for converting and processing as a B&W image than for a color image, or is it just the same as photographing color?

To put it simply - No. Just keep doing what you're doing in colour, then convert to B&W. Do not "desaturated", though. Convert the colour properly from with an editing app like Lightroom.
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Jim Kasson

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Re: Exposing for B&W digital?
« Reply #15 on: September 08, 2016, 10:14:36 PM »

Hi,

In everyday practice, the same exposure will do.

When pixel peeping, technically there could be a (small) benefit from shooting through a somewhat magenta filter, to compensate for the denser Red/Blue filters in the Bayer CFA. That would require less boosting of those channels which would help to reduce noise a bit.

The amount of difference also depends on the final postprocessing, and how image colors are used to change the tonal balance.

Cheers,
Bart

Well, shoot, Bart. I just recommended a CC30M in another similar thread. GMTA?

Jim

GrahamBy

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Re: Exposing for B&W digital?
« Reply #16 on: September 09, 2016, 03:52:49 AM »

Kind of inter-channel HDR that enhances DR for B&W, specially if some strategy is applied to weight more higher SNR channels on each image area.

Ah! Yes of course. Do you know if any existing canned software does this?

That said, when you see something like this shot at ISO 4000, you realise that SNR is often not a priority:

https://500px.com/photo/171748293/huddle-in-the-rain-by-morkel-erasmus?from=following&user_id=10643117
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BartvanderWolf

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Re: Exposing for B&W digital?
« Reply #17 on: September 09, 2016, 06:36:57 AM »

Well, shoot, Bart. I just recommended a CC30M in another similar thread. GMTA?

LOL, pure physics, and creative thinking.

Cheers,
Bart
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BartvanderWolf

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Re: Exposing for B&W digital?
« Reply #18 on: September 09, 2016, 06:58:31 AM »

Hi Bart, your idea is fine (in fact some people use it), when there is enough light to have a good exposure at base ISO. For instance it will produce cleaner shadows in well lit high contrast scenes. But if there is a lack of light (need to push ISO), it would have an overall negative impact on noise. In this situation the more photons you collect the better.

Aside from that, having channels with different sensitivity (i.e. G ending with higher levels in the RAW file) can have some advantage for B&W photography: while G can get clipped in the highlights, you can still 'recover' a nice grayscale gradient from the R and/or B channels there. The G channel will help you in having sufficiently noiseless shadows. Kind of inter-channel HDR that enhances DR for B&W, specially if some strategy is applied to weight more higher SNR channels on each image area.

Correct, although I in principle assume 'correct' exposure, and usually low ISO for ETTR.

You raise a valid point about some potential DR enhancement, being able to choose from different levels of shot noise by channel. I'd add that good Noise reduction software also allows to change the weighting for the Red/Blue and Green bands and the amount of noise reduction.

Bottom line is that there are several benefits to shooting Black and White images as Colour and not Monochrome, and unleash the full potential of tonal control after the fact, during postprocessing. I like Topaz B&W Effects for that, but Googles Silver Efex Pro 2 has somewhat similar capabilities.

Cheers,
Bart
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N80

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Re: Exposing for B&W digital?
« Reply #19 on: September 09, 2016, 08:39:07 AM »

I have mentioned this before but Aperture and Capture One allow you to change Hue, Saturation and Luminance in the color channels AFTER conversion to B&W and in addition to the color sliders within the B&W conversion tool. To me, this seems to offer an even greater level of tonal control compared to only using the color sliders in the B&W tool. It also means you can see the effect of the HSL changes in the B&W image as you change them which is handy.
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