Quarkcharmed
Senior Member
How do you know it's less than desired?
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Underexposure: How to do it right?
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ThrillaMozilla
Veteran Member
Let's see if I can explain it another way.
* With reversal film (slides), an image that was too dark would indeed indicate underexposure.
* For ordinary prints from a photoprocessing lab, underexposed images would probably NOT look too dark. They would simply be lacking in contrast and too noisy. The negative would actually look too light. The dark parts of the image in the positive would look too light in the negative, with no detail or too little detail.
* With digital photography, the appearance of underexposed images depends on the camera settings and any editing that may have been done. Even jpegs straight from the camera may or may not appear too dark, depending on the ISO setting. Depending on how dark they are presented, they may or may not appear noisy.
tony field
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My lady friend, an excellent photographer and artist, refines it this way:
Over exposure happens if my skin turns red after sunbathing. Under exposure happens when my skin remains white after sunbathing.
chrisfisheye
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From your link: https://expertphotography.com/underexposure-vs-overexposure/
"If your histogram graphic is showing a spike at the left or right edge this represents high contrast. You have underexposed and/or overexposed pixels. There will be no detail visible in the extremely dark and/or light parts of the image."
Sorry but he refers to lightness... Histogram is about lightness.
The problem is that in the links you may send, they can start by saying that there is not enough light hitting the sensor. Then you continue to read and you realise that they talk about lightness. Always the same story !
Michael Fryd
Forum Pro
If you insist on the answer in the form of a link: https://www.dpreview.com/forums/post/66354581
By the way here's an example of a situation where two photographers can desire different exposures in the same situation:
Consider a model at the beach with the sun setting behind her. Both photographers want to maximize exposure Photographer A wants in image where the model is a dark silhouette, and the ocean waves have good detail. Photographer B wants good detail in the model, and the background to be blown out. Each photographer has a different "correct" exposure. The exposure that is best for Photographer A would be an "under exposure" to photographer B.
Michael Fryd
Forum Pro
With digital it's far more complicated.
Remember, "exposure" is the light reaching the sensor while the shutter is opened. The three primary factors in exposure are:
- The light coming from the subject
- The aperture
- The shutter speed
If the camera produced JPEG looks dark, the exposure may have been correct, but the ISO may have been set too low. A dark image may just be a result of "under ISO", not under exposure.
chrisfisheye
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In your last case I prefer to use the term under/over lightened because it is more a comopromise with lightness.
Ok in your case it will certainly be about exposure because you shoot during a sunny day . So if this is about exposure this is indirectly. The compromise you make is in fact more about lightness.
You could have the same scenario at higher ISO in low light At high ISO you have less dynamic range so you may choose between the dark or bright part and it will not be about exposure.
Michael Fryd
Forum Pro
There is a difference between increasing exposure and increasing ISO. Both will result in a lighter looking camera-produced JPEG, but the one with the higher exposure will have less noise. Thus the two are not completely interchangeable.
If you want to use custom tone curves to higher shadow or highlight detail, you will find that changing exposure is not the same as changing ISO.
But the bottom line is that the best "exposure" for a give situation depends not only on the situation, but the intentions of the photographer. Furthermore, Exposure is not the same as image lightness. This is trivial to show, as the same exposure will yield different lightness depending on the ISO setting.
chrisfisheye
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Spot on !. This is the impossible question...
For instance, you shoot in low light, of course you would like a clean image but you can not. Is it undereposed just because you wish you had more light ??
"Exposure less than desired" is more than ambiguous, I don't know what this really means...
chrisfisheye
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You did not get the point.
No, it's not. A histogram is a graph that shows the frequency of numerical data using rectangles.
ThrillaMozilla
Veteran Member
Michael, you don't have to explain this to me. I was adding to what you said. Did I not just post a link to the Wikipedia article on exposure? Did I not just refer specifically to the first sentence in said article, which specifically mentions your points 1, 2, and 3? And did I not say "Depending on the ISO setting..."?
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ThrillaMozilla
Veteran Member
If you're trying to make a point, just say it. Otherwise, you're just trolling, and you're not contributing anything to this thread. And when you say "Where are your links?", etc., that's an argumentative attitude that is trolling.
Underexposure is exposure that is too low to give an adequate signal/noise ratio. "Exposure" is well defined. What is deemed adequate is left to the photographer.
You gave us an incorrect definition for exposure, and as far as I can tell, you don't understand what it is. You also don't seem to have made an effort to find out.
Quarkcharmed
Senior Member
That's because Michael Fryd hasn't defined the 'desired exposure' well.
But it's pretty simple if you measure it in relation to the camera output. You don't really know the 'amount of light per unit area', but you know what output you desire.
If you get blown out unrecoverable highlights - the image is overexposed. If it's too dark and has unrecoverable shadows - it's underexposed.
If you want an out of camera jpeg without further editing, your definition of under- and overexposure will be even stricter.
chrisfisheye
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Exactly
I agree.
I mean this is how this should be defined imho and how this is understood by almost everybody, so my opinion is that it is better to keep it this way. Otherwise it creates so much confusion !!!
Quarkcharmed
Senior Member
If your goal was to get a jpeg without further editing, then the exposure was too low for the given ISO.
If you shoot raw and say use 'ISO invariance', the images will look dark initially but they won't be underexposed as it'll be what you expect to adjust in postprocessing.
So again these 'under' and 'over' are measured in relation to the desired output.
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ThrillaMozilla
Veteran Member
Gentlemen, do you remember the OP? He wants to know how to make his pictures "look more dramatic and let the colors pop in the dark."
Have you completely forgotten?
Have you completely forgotten?
Quarkcharmed
Senior Member
No, I answered the OP 's question on the first page, and there were other answers, although I suspect the OP didn't pay much attention to any of the responses.
Michael Fryd
Forum Pro
"Desired Exposure" is simply the exposure desired by the photographer.
Consider someone who claims they won't date someone who is "too short". Would you challenge them to provide a link to a precise definition of "too short"? The answer is that in this context "too short" simply means shorter than the person desires.
When it comes to art, you don't always get a precise technical definition.
Not universally true. I frequently have properly exposed images with blown highlights. It is not unusual for an image that includes the sun, or a light bulb to have the sun or light bulb blown out.
Perhaps you meant to say that a properly exposed image doesn't have any of the important highlights blown. Bit that's just kicking the can down the street. Now you need to precise definition of "important highlights" other than "highlights the photographer cares about".
Similarly, a properly exposed image can have unrecoverable highlights. I have a number of images where I want the model to appear as a dark silhouette. In these images it is perfectly acceptable for the model to be in deep shadow with no recoverable highlights.
There are even times when a photographer may want to have a certain level of visible noise in the image.
Again you've kicked the can down the road. What's your definition of a JPEG that doesn't require further editing? A JPEG that's exactly what one photographer wants may be too dark or too light for another photographer.
A lot of photography consists of creating art. You're going to have a hard time finding a precise definition of the exposure that's artistically best.
Now we can carefully define our goal to come up with a precise definition. For instance we define the correct exposure as one that doesn't blow any highlights, or one that maps the mid tone grey to a certain output level when the camera is set to a particular ISO. However, these are all artificial metrics and don't necessarily correspond to the exposure that the photographer wants.
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The bottom line is that it's a fool's errand to find a precise definition for an artistic choice.
chrisfisheye
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I almost always wish my pictures had more exposure, so all my pictures are under-exposed then ???
Do you have to take into account that you could not have more exposure because otherwise your image would be blurry ??
Is it necessarily a user error ?
You see how fuzzy your concept is.
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