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Internaut
25th April 2016, 08:46 PM
Riddle me this. A photo looks somewhat darker than seen at the point of capture. It exhibits no region of absolute black, and no region of absolute white. Put simply, neither end of the histogram is clipped. Is the photo under exposed?

Beagletorque
25th April 2016, 09:15 PM
Technically no! You can up the brightness I'm post. The camera calculates how much light is required to expose the film plane correctly and keeps the shutter open long enough to gather it (except manual mode!). On average it is correct, but it might not be the same as your eyes.

Sent from my Nexus 5 using Tapatalk

Graham_of_Rainham
25th April 2016, 09:35 PM
A grey card will provide a very good exposure value and neither end will be clipped.

Ricoh
25th April 2016, 11:23 PM
There's no universal correct exposure for a scene, the exposure you choose is personal and it's down to your taste. The camera's brain is set to think a good exposure is 18% reflectance, but it's rare for this setting to be ideal, unless the dynamic range of the scene fits within the dynamic range of the camera's sensor.

I always aim to expose for the key tone in the scene without blowing the highlights. But sometimes the highlights have to suffer. Also it's better to expose to the right simply because most of the digital data is captured at the top end. Also worth noting that the LCD display for chimping is a JPEG representation and in reality the highlights in RAW have some latitude beyond what you see on the camera's display.

Naughty Nigel
26th April 2016, 10:12 AM
Riddle me this. A photo looks somewhat darker than seen at the point of capture. It exhibits no region of absolute black, and no region of absolute white. Put simply, neither end of the histogram is clipped. Is the photo under exposed?

It is difficult to comment without seeing the photograph but it sounds as if the contrast may be too low.

Depending on the contrast (or dynamic range) of the scene it is quite possible for an image to be too dark or too light without being under or over exposed. Adjusting exposure and contrast in Photoshop will quickly and easily provide an image more to your liking.

The difficulty comes with high contrast images, where even with correct exposure you might have clipping at both ends of the histogram. This may be overcome by using a neutral density grad filter, (ideal for landscapes), or taking a series of images at different exposures and combining them into one HDR image.

Imageryone
26th April 2016, 01:13 PM
Quite often the more auto-editing you have switched on in camera eg; grauation, sharpening etc etc, will alter your perceived image. Personally I have everything switched to off, that way I make the decisions, right or wrong :D

Internaut
26th April 2016, 03:18 PM
It is difficult to comment without seeing the photograph but it sounds as if the contrast may be too low.

I wanted to keep the question reasonably abstract, as it's about making sure I understand i) the precise definition of under (or over) exposure and also whether there's a distinction between under exposed and merely a bit dark.

This never happens with my Olympus bodies, btw, beyond the fact that Olympus is known to be conservative with exposure, in many lighting conditions (which is fair enough - once you know that, yuo know what to do).

Bikie John
26th April 2016, 04:01 PM
The key is in the first point:

I wanted to keep the question reasonably abstract, as it's about making sure I understand i) the precise definition of under (or over) exposure and also whether there's a distinction between under exposed and merely a bit dark.

There is no precise definition, as Steve (Ricoh) has pointed out. Normally you want to expose so as not to clip at the highlight or shadow end. You can then sort the mid-tones out fairly easily to suit your tastes (unless you are shooting slide film, which is a whole different ball game - I always thought that slides of birds with white plumage looked underexposed because photogs would keep the exposure down to avoid blowing the highlights).

With some subjects the dynamic range of the subject lets you do this fairly easily. With some it is pretty critical to hit the sweet spot, and in those circumstances it may indeed make sense to talk about "correct" exposure. Some of the time the scene has so much dynamic range that you simply can't catch both ends - or sometimes even hold one end without skewing the exposure wildly one way or the other. Stage lighting can be like that - in those cases you either resort to technical solution like Nigel suggests or use your judgement to achieve the best compromise.

John

Naughty Nigel
26th April 2016, 05:10 PM
I wanted to keep the question reasonably abstract, as it's about making sure I understand i) the precise definition of under (or over) exposure and also whether there's a distinction between under exposed and merely a bit dark.

This never happens with my Olympus bodies, btw, beyond the fact that Olympus is known to be conservative with exposure, in many lighting conditions (which is fair enough - once you know that, yuo know what to do).

I would agree with John and Steve (Ricoh) there is no precise definition for correct exposure, so good judgement at the taking stage becomes highly desirable.

Most of the photography in my day job is technical, so I need to have a clear idea of what I want the viewer to see. If I am simultaneously photographing both bright white and dark blue paintwork I need to decide which is most important to me, as it is rarely possible to get the exposure right for both at the same time; especially in bright sunlight. I therefore need to consider focusing, depth of field and exposure for each and every photograph.

So to sum up I would say that "correct exposure" shows good detail in the point of interest that you are trying to get across. In my case this often means that highlights are burnt out, and/or that there is no shadow detail, or even that I need to take separate photographs of both dark and light coloured finishes. This may be undesirable for a photographic point of view, but it doesn't matter from my perspective as long as I get the point across.

Returning to your question I would say that you should expose for (and focus on) what matters to you. This may mean that parts of the photograph are burnt out or lack shadow detail, but that is not necessarily important, and may even be desirable to exclude detail that would otherwise be distracting.

You may be lucky enough to take photographs that are well within the dynamic range of your camera or film, but these will often appear 'dull' or 'flat' when viewed, and may require 'sweetening to taste'. :)

Edit: I should add that it is not necessarily desirable to capture whites as true white, or blacks as true black, as to do so will usually destroy detail in these extremes of exposure. In practice I would usually lighten blacks and dark blues to show surface texture, whilst bright whites would be darkened for the same reasons.

Internaut
30th April 2016, 05:53 PM
Thanks everyone. Between you, you've answered my question.