mattblaze,
@mattblaze@federate.social avatar

nerditry:
I make mostly (but not exclusively) B&W images (at least for my fine art work). Is it worth using a dedicated monochrome sensor?

Most digital cameras are designed to record color, using a special mask in front of the sensor called a "Bayer filter". This allows color information to be derived from the raw sensor output, which otherwise would just record brightness. But the Bayer filter can also reduce effective resolution of the image a bit.

So what's the tradeoff?

mattblaze,
@mattblaze@federate.social avatar

The advantage of capturing in color even if you're ultimately producing B&W images is that you can do all the color contrast filtration in post-processing rather than with optical filters at the time of capture.

This is a big deal. The color filters used in traditional B&W (e.g., "red 25") eat a stop or two of light and can degrade the image if they suffer any optical defects. More importantly, you're stuck with the filtration you used at the time of capture, with no ability to tweak it later.

mattblaze,
@mattblaze@federate.social avatar

If you capture in color, on the other hand, you make all the color contrast filtration decisions in post, and can tweak it to your heart's content without destroying any information. Modern image software like Capture One and Lightroom makes this easy as part of the B&W conversion process.

But there are still reasons you might want to use a dedicated achromatic sensor and optical filters, at least for some images...

mattblaze,
@mattblaze@federate.social avatar

The first reason, as mentioned, is resolution. For a sensor with a given number of photosites, the Bayer filter reduces the maximum resolving power of the sensor. The effect is fairly small (the Bayer filter is a very clever and highly optimized design), but can be visible depending on the particular contrast and color characteristics of the subject.

I've tested this myself. I'm fortunate to have both the color and achromatic versions of the sensor back for my main camera (PhaseOne IQ4-150).

mattblaze,
@mattblaze@federate.social avatar

In my experiments, I found that for some of my lenses (at the widest end of the spectrum), there's no noticeable difference on any image. These lenses are right at the edge of the resolution capability of the sensor, and just don't project any more detail on the sensor than what the color version can resolve.

But for other lenses (the more moderate focal lengths), the difference is visible, though it depends on the color mix of the subject. The achromatic images are generally a wee bit sharper.

mattblaze,
@mattblaze@federate.social avatar

Honestly, though I care a lot about sharpness (my work involves high resolution large prints, after all), the difference is sufficiently small that it's not generally worth the added hassle and reduced flexibility of having to filter at capture time. I usually just use the color sensor and filter in post, for general photography.

But there's another reason to use the achromatic sensor: capturing outside the visible spectrum.

mattblaze, (edited )
@mattblaze@federate.social avatar

Along with the Bayer filter, most cameras also include a second filter in front of the sensor: a "high pass" ("IR-cut") filter that removes infrared light. This is important because IR, which is plentiful in direct sunlight, focuses at a slightly different plane than visible light. If you don't filter it out, many images (especially in daylight) would be blurry and generally unsharp.

But there's no requirement that the IR-cut filter has to be directly attached to the sensor...

mattblaze,
@mattblaze@federate.social avatar

Many achromatic sensors (which omit the Bayer filter) also omit the IR-cut filter. If you shoot in daylight or in settings where IR is present, you have to add an IR cut filter to the lens to maintain sharpness.

But this also opens a range of new flexibility. Instead of an IR-cut filter, you can instead use a filter that cuts out visible light and passes only IR. This allows you to make (monochrome) images of the infrared spectrum, which can have a dramatically different look.

mattblaze,
@mattblaze@federate.social avatar

IR photography is its own speciality, and requires some practice and experience to predict what you're going to capture (since we can't see IR light with our eyes). The contrast is generally higher. Clear skies (which scatter little IR light) often appear dramatically dark. Vegetation is often dramatically bright. Sometimes the effects are artificial and gimmicky, but it can be used to very interesting effect.

mattblaze,
@mattblaze@federate.social avatar

Anyway, a special camera isn't required for general purpose B&W digital photography, and shooting in color has important practical advantages. For some subjects, an achromatic sensor will produce a sharper image, but that has to be weighed against the less flexible postprocessing capabilities of the raw images. But for IR work, an achromatic sensor opens up a lot of new capabilities.

mattblaze,
@mattblaze@federate.social avatar

I should also mention that I'm only considering technical tradeoffs here. You might decide you want to use an achromatic sensor because you prefer the traditional B&W workflow or to maintain compatibility with a particular film or whatever, and that's absolutely legitimate. I'm discussing here only how the choice of sensor affects the final image.

mattblaze,
@mattblaze@federate.social avatar

It's also worth noting that almost everything mentioned here about workflow applies equally well to the question of whether you should shoot with color film to make B&W prints.

reinoudk,
@reinoudk@mastodon.nl avatar

@mattblaze

From an artistic point of view, when photographing in colour, you'll have to think in colour. When photographing black and white, you'll have to think monochrome, contrast is prime.

Having a disappointing colour picture and think, well this might be better in monochrome, is probably not giving you the best results.

When shooting monochrome, use B&W film. And when you can afford it, a camera with a monochromatic sensor.

(When I used slides, post-processing wasn't even possible.)

mattblaze,
@mattblaze@federate.social avatar

@reinoudk Well, that's not my experience at all. As I discussed, the benefits of a monochrome sensor are very limited, and the creative flexibility provided by having color information available in the raw file (or negative) is a big advantgage.

I suppose there are arguments about "artistic purity" one could make here, but I think those are mostly gatekeeping bullshit.

promovicz,
@promovicz@chaos.social avatar

@mattblaze @reinoudk It would be nice if cameras has B&W color filter simulation. It's not like all B&W is the same... and here, a monochrome sensor may just complicate things?

mattblaze,
@mattblaze@federate.social avatar

@promovicz @reinoudk Many digital cameras can display a B&W preview image (or process the jpg as B&W), but preserve the color information in the raw file so you can make different filtration choices for the final result.

promovicz,
@promovicz@chaos.social avatar

@mattblaze @reinoudk Yes - but it might be nice if they could also preview color filters - like a red filter for sky contrast. Then again, as you say: it's all in the color picture, and I think it's fine to do this sort of thing in post. Film photography would have also had a color preview (!).

mattblaze,
@mattblaze@federate.social avatar

@promovicz @reinoudk Oh, totally agree that that would be nice. But I feel lucky that you can preview in B&W at all.

mattblaze,
@mattblaze@federate.social avatar

@promovicz @reinoudk Ansel Adams would get a rough preview of the tonality and contrast of a scene he was considering photographing by looking at it through a yellow filter. He even had one made with lanyard for carrying around his neck.

promovicz,
@promovicz@chaos.social avatar

@mattblaze @reinoudk Yes... that's where I'm aiming at. My family has a cinema background, that's why I'm into those things... 😅

robpike,
@robpike@hachyderm.io avatar

@mattblaze @promovicz @reinoudk It was more of a dark greeny yellow, Wratten . I hung one around in my neck during my large format days.
https://www.rubbermonkey.com.au/Kodak-3-x-3-No-90-Dark-Gray-Amber-Wratten-2-Optical-Gel-Filter

dan131riley,
@dan131riley@federate.social avatar

@promovicz @mattblaze @reinoudk This is way out of my price range, but it seems like this ought to be possible with a digital camera tethered to a laptop, or even an tablet or phone? (Maybe the Phase One/Capture One kit?)

promovicz,
@promovicz@chaos.social avatar

@dan131riley @mattblaze @reinoudk yes - my old little Canon 1000D could do it on Linux, but model support can be an issue with the required tools. i used that setup for macro, and it‘s also very cheap. 😁

mattblaze,
@mattblaze@federate.social avatar

@dan131riley @promovicz @reinoudk I think you can do that with Phase One Mobile (at least apply a pre-set B&W conversion including filters at the time of capture).

CStamp,
@CStamp@mastodon.social avatar

@mattblaze @promovicz @reinoudk "It's not like all B&W is the same"

B&W has always been an art form, not just stripping colour. Folk shooting it know about colour saturation vs colour tones. Just shoot an image of a playground painted in primary colours. Use of filters to accentuate blue skies or other colours was/is a thing.

If you use software that converts colour to b&w, there will be an area with filter choice, that allows the person to convert as if the image was shot with that filter.

promovicz,
@promovicz@chaos.social avatar

@CStamp @mattblaze @reinoudk Absolutely! But whether it's important to shoot in this or that mode is, I think, up to the artist.

You could stick color filters in front of a color camera, and use B&W preview - and it would end up being much the same as doing it with film photography, with more modern tooling.

CStamp,
@CStamp@mastodon.social avatar

@promovicz @mattblaze @reinoudk Ah, got it. Interesting. There is a preview that shows all the colour channels. I guess there would have to be enough of a demand for camera manufacturers to add that as a preview feature. For now, photographers need to do what they've always done when shooting b&w, understand what they are shooting, though at least now they can see if and where they are clipping.

mattblaze,
@mattblaze@federate.social avatar

@CStamp @promovicz @reinoudk I find the in-camera preview (and histogram) helpful for figuring out if I got the exposure, framing, and focus, but when it comes down to critically evaluating contrast (and adjusting filters), I really want to be home with a large monitor in a comfortable chair.

dan131riley,
@dan131riley@federate.social avatar

@reinoudk @mattblaze I think this had some merit back in the days of film, when I'd have to think about whether I had tri-x or k64 loaded. With digital sensor, I'll compose based on what I want in the final product. Having a color sensor has a lot less to do with the composition than it used to, and converting a "disappointing colour picture" is not the normal use case. You don't have to think in color just because your camera sensor is.

mattblaze,
@mattblaze@federate.social avatar

@dan131riley @reinoudk Yeah, I don't know any serious photographer who doesn't visualize in advance what they're trying to capture. And almost no one uses a dedicated achromatic digital camera, yet excellent B&W digital photos somehow continue to be made by photographers around the world.

mattblaze,
@mattblaze@federate.social avatar

To be clear (I even mentioned this), you should absolutely make your photos with whatever process and workflow works for you. I'm just discussing some technical tradeoffs of a very specific photographic question - how to make digital B&W photos - in this thread.

Maybe you think "real artists" should only be using some particular equipment and method. Maybe I think you should teach your grandmother to suck eggs.

CStamp,
@CStamp@mastodon.social avatar

@mattblaze LOL. Whenever "real (whatever)" or purists start talking, I love to point out that the famous Lincoln portrait is his face on someone else's body. 😃

mattblaze,
@mattblaze@federate.social avatar

@CStamp I didn't know that!

resuna,
@resuna@ohai.social avatar

@mattblaze

> teach your grandmother to suck eggs.

Vintage 'splaining.

florian,
@florian@owo.ff15.eu avatar

@mattblaze can you explain why the effect is small? Naively I would assume that removing the filter would double the resolution in each axis. Is that just a matter of the sharpness being limited by the glass in front of the sensor anyways or is there some smart software doing something similar to subpixel rendering on rgb screens?

mattblaze, (edited )
@mattblaze@federate.social avatar

@florian It has to do with the fact that most light hitting the sensor is not a single pure red, green, or blue, and so you can use adjacent photosites to interpolate approximate RGB value of individual pixels (this is called "de-mosaicing"). But there's no free lunch. Interpolation doesn't always work perfectly, especially when you have images that consist of sharp transitions between exact primary colors.

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