[barondla]

The Pentax A 15 f3.5 ultrawide has a built in filter turret. Is there any advantage to using these in B&W mode vs shooting color and applying filtration digitally in post processing?

Thanks,
barondla

[torashi]

No. Just for b&w film. Taking them in color and applying filters in post saves you the stops you lose by using the filters in the first place. And you have more options (e.g. more tonalities), can compare yellow versus orange versus red, et cetera.

[torashi]

The only reasons I could think of to use them this way would be to use pictures straight out of camera, or if you were learning the b&w process, getting familiar with the effects and practicing.

[photoptimist]

There's no real big advantages, but there may be a couple of minor or subtle differences.

1) The physical filter helps you pre-visualize the effects because you can see it in the view finder.

2) The physical color filters will manipulate the spectrum of colors in ways post processing can't and lead to somewhat different results than can be achieved with post-processing . For example, the orange filter will probably darken yellow-green objects to create stronger green-orange contrasts than will post-processing.

3) Another slight difference might be file size. Shots taken through the physical filters will probably have slightly smaller file sizes owing the the darkening of some of the color channel.

That said, post processing offers more flexibility to tweak the RGB->BW conversion. A physical filter effectively means that your camera never collects full-DR data on the filtered colors. For example, if you use an orange filter, the blue and green channels will be quite dark and not recoverable without noise.

[JensE]

2) The physical color filters will manipulate the spectrum of colors in ways post processing can't and lead to somewhat different results than can be achieved with post-processing.

For regular daylight photography, I normally value the flexibility of choosing "filtration" (i.e. channel mapping to b/w value) higher than 2., but the option does help with specific filtration such as near-infrared (e.g. >650nm) or astro or ND filters - if you can find the respective filter or have them made.

[aaacb]

Depending on your camera, the bw jpeg setting allows to set a digital color filter, which helps preview the change in tonality.

[johnha]

Using the in-lens filter is likely to significantly reduce your effective resolution. The Bayer filter in front of the sensor registers Green, Red, Green, Blue across the sensor, a Red filter will (depending on strength) reduce the sensitivity of the Green and Blue pixel positions the camera needs to interpolate the remainder.

Mono processing in camera will give much better results than a filter on the lens.

---------- Post added 01-05-20 at 05:59 PM ----------

Here's an example with 100% crops from a 645D using the P6x7 35mm Fish-Eye with and without the red in-lens filter (without conversion to mono):

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Last edited by johnha; 01-05-2020 at 11:08 AM.

[dms]

I have a different take on it. There is a difference making a decision on the spot vs. later at the computer. I think making the decision on the spot is better--what you see involves an emotional response that is missing later. If the scene is not moving why not take the picture w/ filter, and then one w/o the filter.

[BigDave]

Keeping in mind, that unless you have monochromatism (you only see B&W), then B&W is really an abstract imaging technique. We only see in color, usually, and understanding how something looks in B&W is becoming a lost art. You can do a B&W JPG and play with the filters, but you will have much better control of the situation if you do this in the editing stage. As has been mentioned, the camera always records in color, but then you task the image to becomes B&W in the JPG.

Personally, I never use the B&W setting. I do the B&W conversion while editing, and I always start with the RAW/DNG file. I will play with the brightness and contrast of the image anyway, so converting to B&W is no big deal. I also do not use Auto WB, and I do use filters for warming and cooling, especially graduated filters, from time to time to save steps in the edits.

[stevebrot]

The Pentax A 15 f3.5 ultrawide has a built in filter turret. Is there any advantage to using these in B&W mode vs shooting color and applying filtration digitally in post processing?

Thanks,
barondla

Based on personal experience...

If you are shooting B&W film, use the lens' built-in filters.

If you are shooting JPEG digital using the "BW/Monochrome" custom mode, use the in-camera filter adjustments (info button) for that mode.

If you are shooting RAW and processing in post to B&W, do your spectral curve adjustments in post.

Yes, I have tried using B&W filters for digital capture and even with fixed white balance, it really does not work very well. Of course, YMMV.


Steve

[stevebrot]

I have a different take on it. There is a difference making a decision on the spot vs. later at the computer. I think making the decision on the spot is better--what you see involves an emotional response that is missing later.

What one sees in the viewfinder when a filter intended for B&W film is in place provides few clues as to what to expect from even a B&W film capture. As for missing the emotional response, the image below was captured full color with the intent to process to monochrome. I used a polarizing filter to increase contrast in the sky at capture. In PP I bumped gold-tones in the trees and grass and decreased blues. The effect is much the same as if I were using a minus blue (Wratten #12) at capture to a panchromatic film.




Steve

[kypfer]

One has got to remember that the physical coloured filters are adjusted to respond to the way black & white film reacts to daylight, which is different to the way the human eye or the sensor in a DSLR interprets it, so simply putting a piece of coloured glass/gel in front of (or within) your lens will not give the human viewer an impression of how black & white film would have responded.


Best practice seems to be to ignore the filters completely and rely on digital processing to deliver an image that you find pleasing ... the only exceptions to this would seem to be where ONLY the infra-red or ultra-violet portion of the spectrum are wanted and "normal" light might mask the result. In these cases the usual i/r or u/v pass filters would be fitted to the lens (or internally to the camera), bearing in mind that even then, the sensor may have a different response to the appropriate film so the results may only be an approximation of what might have been achieved with film.


Obviously YMMV

[JensE]

the infra-red or ultra-violet portion of the spectrum are wanted

... or if only certain parts of the spectrum are unwanted, such as in "light pollution" filters for the night sky, blocking the orange sodium emission (and some potential other narrow bands) of classic city lamps. Or, even more specialized filters are used, when only other visible parts of the spectrum are wanted, such as the emission lines of Oxygen (OIII), Hydrogen (H-alpha) and Sulfur (SII) for deep sky photography. As noted earlier, none of those are normally relevant for daylight use.

[dms]

What one sees in the viewfinder when a filter intended for B&W film is in place provides few clues as to what to expect from even a B&W film capture. As for missing the emotional response, the image below was captured full color with the intent to process to monochrome. I used a polarizing filter to increase contrast in the sky at capture. In PP I bumped gold-tones in the trees and grass and decreased blues. The effect is much the same as if I were using a minus blue (Wratten #12) at capture to a panchromatic film.




Steve

My thinking is the emotional response to the moment--the visual one, sounds, emotional state, etc. can cause one to choose (for example) a red filter vs. a milder yellow one, and that state of being will pass after taking the picture. Later at home w/ computer your thinking about what is the right feeling will be different. I am assuming the effect of B&W filters on the image (previsualize I believe is what Adams called it) is something one has--for the purposes of my post--or can/will develop; but whether rudimentary or advanced, I still feel the choice(s) one makes when confronted with the scene is likely to be different (for emotional reasons) than that hours later.

[kypfer]

A second thought on the way the human brain/eye perceives a b&w rendition of a colour image :- "back in the day" I remember the suggestion/recommendation that one might view the scene through a dark purple filter the give to human brain a representation of how a scene might look in monochrome. A piece of transparent purple cellophane was mounted in a cardboard frame and held to the eye for assessment purposes. If one has access to a source of such material, it might be worth the effort