Exposure is not how dark or how light an image looks!

If you refer it to me you are mistaken. Not only I shoot and process a lot of MF and LF film myself, I repair and adjust film cameras for my friends. People of my age spent 30+ years shooting film before it became possible to purchase a digital camera.

It depends on the goals of the photographer for the final image.

Mine are pretty simple - get as much light as possible onto the sensor while the shutter is open and within my dof and blur requirements without clipping important highlights.

Try a magenta filter (CC40M) on the lens when shooting at daylight, you will get more red and blue light onto the sensor.

If I need more red and blue light to get the final image I want, I'll keep that in mind.

Here goes optimal exposure ;)

The CC filter trick is a way to get a higher SNR in the final image. I wouldn't recommend it for beginners, though. You may have to make your own color profiles to get the best results. And, of course, the exposures will be longer all else equal.

The definition of optimal exposure will vary greatly among photographers depending on their needs and goals.

There is no one size fits all definition for optimal exposure.

I just simply post what it means for me.

YMMV ;-)

Exposure - amount of light striking the sensor per unit area while the shutter is open.

Optimal exposure - the maximum exposure within my dof and blur requirements without clipping important highlights.

The only point I'm trying to make here is that "optimal" is a peremptory word ;) "Optimized, given the circumstances", if one asks me...

when do you calculate just exposure values only before taking a photograph. or shood i use asa 64 film to shoot a concert tonight ;-)

Sometimes the lighting is unbalanced, often under artificial light. Whenever WB deviates away from around 5000K either the red channel or the blue channel will start to be relatively underexposed. Also, if you are trying to get the background not to blow out in a backlit scenario, then even in broad daylight you could have both the red and blue channels relatively underexposed; conversely, maybe only one or two of the channels is overexposed if you are going for an optimal exposure of the subject in a backlit scene.

I have hardly used my CC40M filter since shooting primarily with a Nikon D300. Nowadays, it's my preferred approach to slowing down my shutter speed by a stop when that's something I want to do, so that filter is still in my landscape kit.

At 5000K with a neutral subject, both the red and blue raw channels will be underexposed wrt to the two green channels, with most Bayer CFA cameras.

Good point. That's why I wrote "relatively;" otherwise I'm "underexposing" practically every time I don't use my CC40M filter, and even more so every time I turn on Auto-ISO.

I was confused by your use of the word relatively. I thought you meant wrt the green channels.

It does if you shoot film.

You may want to refer back to the original post in this thread; the first half of which, discusses exposure as it relates to film.

dprevived.com/t/exposure-is-not-how-dark-or-how-light-an-image-looks/495/post/3288/

I hope film can be discussed on film forums, and not in a casual manner.
dprevived.com/t/odd-film-analogies/1033/
Wrong film paradigm is why we don't have raw histogram and a mess with ISO. It also causes inadequate camera metering and controls.

Returning to the original post in this thread...

OK

OK, exposure and processing have roles to play in shaping the response curve. You could also gain and have excessive contrast in addition to losing it, but it's reasonable so far.

None of this controlled? Well, there's some latitude in the image creation path which precedes making a print, but there is a noticeable impact on the appearance of your final print — including how dark or light — if the exposure is too far off!

How dark or light prints will look is not "determined" at print time. The critical factors in that determination began with the exposure used at the time of image capture and proceeded from there.

You can easily make prints of varying quality, lightness, and darkness from a thin, normal or dense negative. Making high quality prints from a thin, normal or dense negative is not all that easy. Some degree of over or under exposure allows for satisfactory prints; but the greater the degree to which exposure is off (over or under), the worse your print quality will be.

Please don't tell this to beginners as it implies that exposure plays no role as you've worded it in this sentence. How you expose an image; how you process an image; how you print an image; contributes to how dark or how light an image looks! All the links in the imaging chain combine in the end to determine your final image quality.

I'm generally in favor of simplifying explanations for a broad audience, but you can over simplify to the point of information becoming muddled and unhelpful.

Mr. Borg does bring up an interesting point. Suppose you are shooting a landscape where the dominant color is green. Assume you are shooting at base ISO, and have picked the maximum exposure that doesn't blow out important highlights.

On a whim, you look at raw data from the capture. You happen to notice that the green pixels (those behind the green filters in your Bayer Pattern sensor) have a much higher exposure than the red and blue pixels. Perhaps if you increased the exposure by one stop the blown pixels would all be green pixels, and none of the red or blue pixels would be blown.

If your goal is to maximize exposure, you could put a filter on the lens that reduces the green light by one stop, and leaves the red and blue light untouched. You could then open up the aperture by one stop, or use a one stop longer shutter speed.

The net result is that your green pixels stay at the same exposure, but you have increased the exposure in the red and blue pixels by one stop.

By increasing the exposure on half your pixels (25% of the pixels are red, 25% blue) by one stop, you have increased total light captured by 1/2 stop.You are now capturing more total light, and therefore will have a less noisy final image. Yes, you would need to compensate for the filter when processing the raw data, but that's a doable task.

So if your goal is to do everything you can to maximize the light captured, then this is a technique you should consider.

On the other hand, at some point the quality of an image is more than good enough. You reach a point where additional increases in quality do not justify the resources needed to get those increases.

All real world captures have noise. If the noise is low enough, then you may be able to measure the noise, but it won't be visible to the unaided human eye. One can make a reasonable case, that once you reach the point where the noise is not visible, there is little benefit to further reductions in noise.

Perhaps you are shooting without a filter, and your images have no visible noise. You could use Mr. Borg's technique to further reduce measurable noise, but that incremental reduction may not justify the time, effort and resources needed. Of course, whether or not that additional reduction is worth it, is going to depend on the situation. In some situations, you may need to squeeze every drop of performance from your camera. In other cases, you may be able to use a simpler workflow, and still get results that meet your needs.