What does the correct amount of exposure look like?

[dxin]

<p>I know that a flash meter is a good tool to determine the amount of exposure.<br>

But ultimately we always judge the exposure perceptually. However we adjust exposure, before taking the picture or during post processing, we do whatever we can to make the picture <em><strong>look good</strong></em>.<br>

<br />Here is a picture I took. The meter measures a F4.5. I adjusted the camera to F2.8 and the picture looks good on the camera's screen. But when I loaded it to my computer, I still found it a little dark.<br>

Then I post processed it to +0.7EV to make it look good on the computer, but at the same time it looks over exposed on the camera.<br>

<strong>My question is, what does the correct exposure look like?</strong> A quick answer might be, <em>which of the following pictures you think looks better?</em><br>

How do you determine the total brightness of the picture? Meter? Histogram? What if the it looks perfect on the meter and histogram but the picture is just a little bit darker/brighter than you want it to be?<br /><br>

Any input will be helpful. Thank you.<br /><br>

<br>

<img src="http://www.freeimagehosting.net/newuploads/ulh3p.jpg" alt="" width="698" height="471" /></p>

<p><img src="http://www.freeimagehosting.net/newuploads/8fusz.jpg" alt="" width="696" height="460" /></p>

[User_6502147]

<p>You might want to use 18% grey card. Check that against the meter and histogram. Also, hope you have your monitor calibrated properly. Most DSLR's have pretty accurate histogram, but not all. Anyway, once you get the tweaks out of the system, you should know where you stand. Some of the built-in camera light meters can read little off, so you always have that to deal with, but this too can be corrected.</p>

<p>Anyway, just make sure you read the "appropriate" surfaces correctly....you can point the spot on the darker surface and the resulting pic is overexposed. Just saying....</p>

<p>Les</p>

[dxin]

<p>I'm not sure the images are displayed. I just reloaded them.<br>

http://i502.photobucket.com/albums/e426/d_xin/R0040078_01_zps0146ff35.jpg<br>

http://i502.photobucket.com/albums/e426/d_xin/R0040084_zpsd8ee3b1a.jpg</p>

 

[howard_m]

<p>there's nothing calibrated or magic about the brightness of the camera's back display. I think I have mine set quite low. Like TV's, they're always too bright from the factory. Of the two images I see in this thread, I'd say both are wrong, top is too dark and bottom is too bright by about 0.5 stop. The fact that it's all metallic and shiny doesn't help the analysis.</p>

[SCL]

<p>Don't use the screen on the back of your camera to accurately determine how the picture will look, either in print or online...it just isn't accurate enough or calibrated. Your assessment should be done either thru the histogram on your back screen, or through proper post processing software on a calibrated monitor.</p>

[Tim_Lookingbill]

<blockquote>

<p>Then I post processed it to +0.7EV to make it look good on the computer, but at the same time it looks over exposed on the camera.</p>

</blockquote>

<p>Not sure how you are seeing a post processed image both on your computer and camera. Or are you saying you are equating editing software's added .7EV to increasing exposure incamera? If the latter, the two can't look the same not just because of camera LCD calibration but the fact you're increasing exposure on cooked and gamma encoded jpeg pixels after they left the camera's linear sensor and processor. They will never look exactly the same nor will they deliver pleasing results for reasons explained further.</p>

<p>Even if you were increasing exposure through a Raw converter on the linear data each converter exhibits variances with their version of the exposure slider where some act more linear over others. See the emulation posted below of curve type exposure on gamma encoded data compared to applying a linear curve which exhibits more clarity (better look) at the sacrifice of blown highlights which I've indicated with the red arrow. </p>

<p>In addition electronic sensors don't respond linearly and/or the same to any given lighting characteristic the more exposure is increased where the mids and upper mids lose clarity of detail the closer to full saturation of the sensor so a tone curve is applied to prevent premature highlight blowouts which renders a flatter response which you can see in the sample emulation below. </p><div></div>

[frode]

<p>I usually distinguish between exposure and presentation. You cannot adjust exposure in post processing. Exposure depends solely on the exposure time and aperture. Some will also include ISO, but strictly speaking ISO is not part of the exposure. It is the sensitivity (for film) or gain (for digital cameras).<br /><br />When it comes to the exposure you are the boss, the one that have to evaluate the scene and decide what is the correct exposure. With respect to light, a correct exposure will normally be the one that is judged by you to capture all important details in the scene. That is the parts of the highlights that you deem too important to burn out and the parts of the shadow details that you deem too important to be drowned in noise or grow completely black. A wrong exposure is consequently the one that do not capture the details you want to capture. In some cases you cannot have it correct in both ends. You will have to prioritize what is most important. Is it the sunlit snow on the mountain top or the dark green conifers in the shadow of the valley? You decide. Or you will have to fall back on other techniques, such as graduated neutral density filters or HDR. There are also two other aspects of exposure, and that is exposure time vs. movements and aperture vs. depth of field, but you asked about light, so I'll leave those out.<br /><br />For presentation, you are also the boss. You decide whether the image is going to be presented light, dark or somewhere in between. You may even decide to burn out the highlights you managed to capture in the exposure. There is no law claiming that you must present all the details you captured or are able to capture. You decide. It depends on what you will show or communicate. The same image may be presented in several different ways. What you cannot do however is to decide afterwards that you want to present the details that you (consciously or not) decided to burn out in the exposure. In this case you would have to conclude that your exposure was wrong.<br /><br />Remember though that when you look at the camera's screen, you look at a JPG representation of the RAW image, not the RAW image itself, and the RAW image will quite often (almost always) have more details in the highlights and shadows than the JPG will show you.<br>

<br /><br />Have a look at this (random googled example) page:<br /><br />http://www.mora-foto.it/en/tutorials-gimp/high-key-low-key.html<br /><br />You see an example of a single image presented in three different ways, high key, low key and what is termed "normal". None of them are wrong when it comes to how light or dark they are presented. But look at the finger tips of the model. They are burnt out, even in the darkest image. It is of course easy to do this on purpose in post processing, but I doubt this was done on purpose (but it might have, I am not the one to decide). If it was my image I would have deemed it as wrong exposure (overexposure). Those highlights are important enough to me that I would have "darkened" the _exposure_ (smaller aperture, shorter exposure time) to obtain some details in the finger tips. Lower ISO to obtain more "headroom" for the highlights is of course an alternative, as well as changing the lighting.</p>

<p>Cheers<br>

Frode Langset<br>

(I hope this was at least of some help. And excuse my English, it is not my native language)</p>