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reducing overexposed images in posts

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reducing overexposed images in posts

Postby SSSdave » Wed Sep 28, 2016 9:54 am

The number one problem that inexperienced photography members have posting images not only in the HST community but on all Internet boards and to social media sites is overexposed images. Its absolutely epidemic and many people who do so don't seem to care probably because they see so many others do so. But it doesn't need to be that way even for least savvy computer users. One can see many poorly exposed images posted in our HST threads so I will make a simple input herein to help those who haven't figured it out themselves yet.

All digital cameras, even the most automated ones will have Exposure Compensation controls because that is one of the most important settings for taking pictures. More expensive digital cameras may have sophisticated exposure analysis software that in their AUTO mode figures out the correct settings such that one does not need to regularly manually adjust Exposure Compensation. However the majority of cameras do not and instead may have a list of special SCENE modes one can select. However not many people will bother to change from standard AUTO mode into one of the special Scene modes simply because say they are taking a picture in the green forest on one shot and then about bright granite the next. And that results in lots of overexposed captures.

The way digital camera sensors work, it averages exposure values in either zones within a frame or more classically a central zone in the lens frame. For many subjects, the range of scene brightness values is beyond what a camera can capture. The default Exposure Compensation, aka EC, value is always defaulted to zero 0 and if such a subject is shot, the result may be shadowy elements darker than what our eyes see, bright objects much brighter than what our eyes see, and middle range brightness elements exposed well. The solution is to change the EC to a lower underexposed value. The setting are often in 1/3 Stops thus a setting of -1/3 is the first lower setting and -2/3 the next. I often recommend to people that wish to remain in their AUTO mode and that don't want to bother adjusting compensation for each subject to use -2/3 and let it set there.

The result of setting EC to -2/3 will however cause many captures to be a bit dim. That is only an issue if one posts images directly from camera memories without any post processing at all that of course is the way some post. Even the simplest photo processing applications allow one to adjust the brightness and contrast of captured images so to do so should be trivial even to the least computer knowledgeable users. Actually anyone that post images on the web probably is already using some application because resizing images down to monitor dimensions is a necessity before posting. Almost all experienced users tend to underexpose a bit with all their images because post processing such images to a perfect level is simple. Alternatively it is impossible to fix overexposed elements in camera shots because the information in bright elements was clipped thus never captured.

There will be situations where setting to -2/3 will result in overly underexposed photos so there is value for any digital camera users to learn some basic about exposure. For instance a person standing about a bright white granite area or in front of snow is likely to come out looking very dark because the sensor is tricked into thinking the scene is bright so compensates the opposite direction reducing the exposure. Thus the optimum EC level might be at +1/3 or +2/3. Likewise conversely making an exposure of an evenly dark subject may result in an unnaturally bright capture thus a setting even below -2/3 may be optimal. The wisest strategy in such a situations is to take a test shot, review the capture, and then readjust if necessary to find the sweet spot. In any case these more extreme situations are uncommon so just using -2/3 will alone be a HUGE improvement over the standard zero default setting. Many cameras have Histogram displays that will show if there are any clipped overexposed elements but otherwise just keep brightest elements at a reasonable level. There are many Internet sites that will go into more depth about the above.

So set your Exposure Compensation to -2/3 and the perform minimal post processing bringing up brightness levels for shots that need such.

http://www.cambridgeincolour.com/tutori ... tering.htm



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Re: reducing overexposed images in posts

Postby Goat » Fri Jun 09, 2017 3:24 pm

Thanks for the info Dave. Here's a dumb question from a learning beginner. Say you have some darker foreground, a hemmed in lake in shade, and a bright background, a beautiful ridge line blasted by sunlight. How would you use exposure compensation in this case? Would you risk loosing information in the dark area by turning it down?
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Re: reducing overexposed images in posts

Postby maverick » Fri Jun 09, 2017 3:37 pm

Hi Goat,
Either use a neutral density filter or use exposure blending (which is what I prefer). Here is one of many video's on exposure blending:
https://www.youtube.com/watch?v=lQhtqGLglww
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Have a safer backcountry experience by using the HST ReConn Form 2.0, named after Larry Conn, a HST member: http://reconn.org
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Re: reducing overexposed images in posts

Postby Jimr » Fri Jun 09, 2017 4:38 pm

Goat wrote:Thanks for the info Dave. Here's a dumb question from a learning beginner. Say you have some darker foreground, a hemmed in lake in shade, and a bright background, a beautiful ridge line blasted by sunlight. How would you use exposure compensation in this case? Would you risk loosing information in the dark area by turning it down?


Since you asked the question, why not start here with furthering your understanding. I suggest starting with understanding dynamic range and camera sensors. This is a concept that needs to be understood. Once you get comfortable with this, you will start to "see" that a scene may have too large of a dynamic range to capture with one exposure without blowing out either the highlights or shadows. Then start learning what tools your camera avails you. Can you vary how it determines exposure? Evaluative, center weighted, point? Does it give you control of the white balance it uses? etc. Then you can start playing with exposure bracketing, either manually or as a setting on your camera. Then you can start learning about blending. Does your camera give you the option to shoot in RAW format? This is more than enough to start with.
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Re: reducing overexposed images in posts

Postby maverick » Fri Jun 09, 2017 4:43 pm

What camera are you using Goat?
I don't give out specific route information, my belief is that it takes away from the whole adventure spirit of a trip, if you need every inch planned out, you'll have to get that from someone else.

Have a safer backcountry experience by using the HST ReConn Form 2.0, named after Larry Conn, a HST member: http://reconn.org
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Re: reducing overexposed images in posts

Postby Goat » Sat Jun 10, 2017 3:30 am

I have a newly acquired RX100. It can shoot raw and adjust white balance, but I'm not sure what method it uses for determining exposure. I've started digging into the concepts of bracketing. Lucky for me I also have CS5 on my computer at home, though it would be more useful if I knew how to use it. I also have the book Understanding Exposure on order.
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Re: reducing overexposed images in posts

Postby fishmonger » Sat Jun 10, 2017 7:52 am

I shoot RAW with Nikon DSLRs, usually -0.7 on the dial for exposure compensation. There are many more f-stops of recoverable dynamic range in the shadow areas than highlights so the risk of blowing out stuff is reduced. In critical situations when I really want the shot, I bracket and usually shoot a -1.3 fstop as well, rarely anything above actual exposure.

The rest is then all handled in post by adjusting everything base don the histogram, white and blackpoint (if applicable).

Auto white balance is ok as long as snow is in the picture, but in the deep green woods, all that goes off the charts towards magenta. I generally make slight corrections to white balance in post as well.
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Re: reducing overexposed images in posts

Postby SSSdave » Mon Jun 12, 2017 4:13 pm

Your camera software controls are very similar to my A6000.

http://docs.esupport.sony.com/dvimag/DS ... slist.html

On this contents page for the RX100, the following will be of most interest for exposure control:

Aperture Priority
Manual Exposure
Scene Selection
DSIP (Display Contents)
Exposure Comp.
ISO
Metering Mode
DRO/Auto HDR

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