the operation is designed to imitate/simulate the use of the physical exposure controls you have on a camera. If you insist on being pedantic about the “exposure” being what takes place in the camera than call it post-exposure or something. If there was any other exclusive terminology for this adjustment already in existence we would have heard it in this thread already I guarantee it.
luminance, the term you seem to prefer in this situation, could just as easily refer to the light falling on the subject in the scene you’re photographing (much like exposure refers to your camera settings in your mind) rather than being some derivation of the brightness of pixels in your editing software. Added to that, some image editing software has “luminance” sliders which may operate quite differently to “exposure” sliders.
English is just one of those languages I’m afraid, we don’t have jargon for everything under the sun - specificity often gives way to practicality.
Just a meta note about that. Mainly from work I’ve experienced that some folks like discussing things to the roots (sometimes in circles, though) and other folks don’t like non-productive discussions and would rather “get things done”. So I try to tolerate both sides …
True, I got the definitions mixed up. Luminance still applies to the light at a point in the scene after it has bounced off the subject though - i.e. incident metering measures illuminance, reflected metering measures luminance.
Either way an increase or decrease implies a change in the power of the light source just as much as it does some arbitrary gain function in software.
Fortunately, if someone posts a thread looking for assistance in how to increase the luminance of their photo in darktable, I’ll know given the context that they’re not trying to figure out how to make the sun brighter. Likewise if they were to ask about how to increase the exposure of their photo, I’m not going to recommend booking another holiday to Iceland so they can try the shot again at f/4.
Well. according to the Wikiepedia-article on luminance it “describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls within a given solid angle”. So I actually think you were right in the first hand.
That’s part of my problem, there are such a lot of technical terms that are almost alike …
And as already mentioned above, one thing that complicates this is the difference between perceptual terms (which could be brightness or lightness) and non-perceptual terms (which I now tend to believe is luminance) – and when is it appropriate to use one or the other?
I don’t think we need to go to Iceland or the sun for finding an answer, though. If there may possibly be different sources/causes for such an amendment, does it matter? E.g. a decrease in my potential energy happens anyhow independent from whether it’s caused by escalator or me falling down.
In the Exposure module we find this main slider, by many regarded as the pillar of image processing, labelled “exposure”. A fairly straight forward mechanism that we all understand.
However, “exposure” is what happened previously in the camera, (the density of light hitting the camera’s sensor, based on the illumination level, shutter speed and aperture value used). So I wonder what is really the correct term/description of what this slider adjusts?
I don’t use darktable but there is an amazing number of people who think “exposure” means how bright a post-processed image is!
I am with you and have actually hacked the “Exposure” slider label in my raw converter to read “Brightness”.
I certainly agree that having so many terms is complicated and often difficult, but personally I think we’re better off with the simple - perhaps less specific terms - we have in the current interfaces, than we would be trying to come up with even more terms to properly delineate all these different ways of interpreting brightness (as long as someone on the back end knows what’s going on).
While I’d like to think that I, and everyone else on this forum, takes much greater interest in what’s happening under the hood of their editing software compared to most photographers out there, at the end of the day it doesn’t really matter if I understand exactly what any given slider is doing and why it was designed that way, I really only care about how my final photograph looks on screen and in print.
Really!??? To me that’s as if ‘white balance’ was taken to refer to someone with white clothes balancing on a step ladder. I fail to see any connection whatsoever.
That sounds critical which wasn’t my intention, I’m just shocked into incredulity.
My take on all this is that exposure is the correct term. As has been said already, it’s the same effect as adjusting ISO in camera, and as such also simulates a change to in-camera exposure.
As far as I’m concerned there’s no room for improvement, regardless of beginners or professionals.
It’s completely and utterly the correct term…
And I know the original question was not about changing the name of the control - I don’t think I can help with that question though.
Really!??? To me that’s as if ‘white balance’ was taken to refer to someone with white clothes balancing on a step ladder. I fail to see any connection whatsoever.
That sounds critical which wasn’t my intention, I’m just shocked into incredulity.
My take on all this is that exposure is the correct term. As has been said already, it’s the same effect as adjusting ISO in camera, and as such also simulates a change to in-camera exposure.[/quote]
Sounds like all those “exposure triangle” articles where we are told that ISO changes the sensitivity of the sensor!
[quote]
As far as I’m concerned there’s no room for improvement, regardless of beginners or professionals.
It’s completely and utterly the correct term…
So, what are the units of exposure in your obviously non-technical world?
ISO says exposure Hm = lux-seconds at the sensor - totally unaffected when people waggle the so-called exposure slider.
Just give me everything in stops (EV) please. Doesn’t need to be made any more complicated than that.
I plug “1” into the exposure module and its practically the same as had I gone up three clicks on the ISO dial of my ISO invariant camera. Perfect. What more could one ask for.
My experience as a newcomer to dt, was indeed that I met lots of new specialized terms that I have strived to understand and internalize. (May be it feels more heavy than it really is, from also starting to read many advanced discussion here on the forum, and I further realize that a native English speaker may have a better comprehension of some of the terms at the outset.) Just recently a new color module was released which introduced even another term for a dimension of color (“purity”), apparently because it was felt to be more precise and something different from chroma, saturation and whatever terms already in use. I’m aware that this can be seen as a reflection of there not being one unified model/theory for light, colors and images, and that the landscape of vision studies fractures into many different fields, and these fields do not agree on much of anything. – But, actually, that dt seemed to be an image processor that aimed at “being scientific”, appealed to me.
Yes, but there is a necessary linking between those two parts: How we use those sliders to get to that “final” photograph. Many of the relevant terms have an inner connection, which also may reflect a connection between functions they relate to. So I feel that learning and understanding these terms increases my understanding of image processing and aids my skills development with dt. When making notes and writing about image development I also like to know that I use precise wording.
This topic certainly produced some interest and different points of view, which I like to see on this forum.
I don’t own a Fuji camera but I really like them because of the models with invariant ISO. So in the camera you set the aperture, the shutterspeed and nominally the ISO. But the ISO can be effectively changed by adjusting the exposure slider in DT and other programs. The ISO can be changed from 100 to 1600 ISO without any compromise to noise. Bloodly amazing stuff. I look forward to when all sensors can produce images that do this. Then the exposure slider’s name will be less controversial because that is what it truly is doing.
OK, point taken. I guess I was asking for an uncompromising reply.
And yes, my world is largely non-technical. I can at least handle the quoting system in this forum though. (hint hint)
I guess I should have prefaced my opinion with the disclaimer that is is only my opinion.
Carry on everyone! I’ll bow out of this discussion, as it’s over my head.
[edit: not suggesting that I don’t like this kind of discussion - it’s all educational!]
I think the issue with this is that brightness is perceptual. When I think about it more your preceding comment is well taken that initially exposure as a part of the capture process is determined by a combination of settings, then in place of film there is the ability of the sensor to have the DNR and fidelity to record this faithfully as best it can given the limitations of each sensor. After the necessary processing the analog light signal ends up as a digital value that gets passed to the software. If we agree that the camera will do a good job during this capture then we have a value that is representative of what you asked the camera to capture (the exposure)… This value is passed along in the various steps of the post processing and at the input into the exposure module that value is doubled with each + EV step. So to me this is a gain or perhaps relative exposure adjustment. I say relative if you assume exposure is given by the initial value provide by the camera ie as it was exposed from the scene by setting iso, f-stop, shutter speed. So using the slider is changing the image in a predictable way from 0 (the captured exposure of the image) to new values that are altered relative to this initial exposure… Overly simplistic maybe ??
My thoughts against brightness is that it is a perceived attribute and so a 1 EV relative change introduced by the slider might be perceived as more bright by some than others even though they are both looking at pixel data that has been doubled… along with this are the nuances around perceived "brightness’ in an image
So personally if there was a need to align the slider “name” or terminology to its function for me exposure gain or relative exposure would seem to be appropriate if you were willing to limit the notion of exposure to be what happens in the camera as a result of the capture settings used…
From the article you link to: “Brightness is our perception of luminance”.
So if the perceptual aspect is problematic, why not rather going for the underlying luminance?
(They go on to talk about the freaking Exposure Triangle, so take that with a grain of salt…)
That the slider that alters the image values does so in a scale similar to the energy relationship of light in the scene is just fortuitous. It alters the measurements in a way changing the actual Cambridge exposure would, but with very different consequences.
“exposure” in software is a misnomer, one that you just need to understand in order to talk to people…
Seriously? It was designed and written by a human, do you really think they chose to use that scaling on a whim and the shared relationship is nothing more than a convenient accident?
Maybe the author is around and confirm or otherwise themselves, but it was surely implemented that way quite deliberately.
This kind reasoning is an etymological fallacy. “Exposure” has a lot of meanings, and you will not find them all in a (general) dictionary.
For better or worse, the meaning used by Darktable is established now in the world of digital photo processing. Most people understand it, and if they do not, there is always the manual.
Incidentally, almost all modules in Darktable feature a lot of technical concepts, using common words with a highly specialized meaning. Eg various color dimensions in Darktable also use everyday words, but if you want to figure out “purity” in this context from the Cambridge Dictionary, you are facing a difficult task.
