avoiding this problem.....

[XR3ste]

I use a 400D and would like some good advice on what settings you more experienced users would apply to the 400D to avoid the problem in the Picture, The problem is that the young lads face has been "overexposed" but the rest of the pic is ok. Can anyone help me out on how to avoid this and what settings i could have used. Any help would be most appreciated. Thanks
http://i7.photobucket.com/albums/y251/efiste2/dadnluke1.jpg

[tonydee]

There are two aspects to this... learning to ensure you don't overexpose when taking a picture, and tweaking the resultant picture in post-processing.

To ensure you don't overexpose, you can use the "disp" (display) button on your camera to make overexposed parts of the image blink when you've reviewing them or playing them back. The same button can cycle the display modes to show a histogram (graph) of the brightness levels throughout the image. You want to make sure that the graph trails away to nothing before reaching the right end: there should not be a spike or sudden drop-off from height at the very last pixel on screen.

Your histogram currently looks like this:

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I displayed this using the free "Histogram Viewer" plugin for the Firefox web browser, but you can see histograms on your camera, in the Canon software that came with your camera, and in many other image editing programs including the free gimp ( http://gimp.org ) and far-from-free but category-leading Adobe Photoshop.

In this histogram, the black-grey-white gradient at the bottom in an axis for the brightness of areas in the photo, and the height graphed above that brightness level reflects the surface area inside the image with that brightness level. We can see that your image almost touches the right end of the graph, but doesn't "clip" or spike there. So, you don't have significant area of brightest white - such areas tend to indicate that a some of that area was even brighter in reality but the camera was so flooded with light that it couldn't differentiate the intensities, leading to an (almost) irreversible loss of detail.

As you image captured everything without clipping, you can still adjust the brightness and contrasts throughout the image effectively. The easiest way to do this in post-processing software is using a "curves" adjustment. Any of the software packages mentioned above can do this - I have used GIMP below. Curves is a bit like a histogram in that the camera-recorded brightness is displayed along the bottom, but this time there's an initially diagonal line indicating the desired image brightness on the x axis. You can click on the line and drag parts of it up and down to adjust the contrasts and brightness throughout the image. For your photo, you need to put a point perhaps 10% from the right end of the diagonal line, and drag it down a few pixels until the boy's face isn't over bright, trying a little left and right until it looks best. Then add another point a bit to the left of the first to bring the line back towards the diagonal so the darker parts of the image aren't made even darker.

This will look something like this:

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For best results, always shoot RAW, and you'll have all the subtle detail that the camera recorded available to make sure you get the best result after doing a curves adjustment. JPEG images throw a lot of important information away, and are only really useful if/once everything in image is the way you want it.

Cheers, Tony

[Benji]

The boy's face is closer to the edge of the window and is getting more light than the gent behind him. Using an on camera flash would have evened out the lighting on both faces. If you wanted to use available light only, you have two choices, move the boy back (preferred) or move the gent out.

If you shot this in Raw save the image twice, once with the boy's face properly exposed and one with the gent's face properly exposed, the in Photoshop combine the two so you have both faces properly exposed.

Benji

[Grimlock]

Yup, what these guys said. Some good advise here.


I would personally like to thank TonyDee on posting the Histogram plug-in. This is too cool. :)


Carry on...

[XR3ste]

Thats great advice, thanks so much. This is a photo ive tried to capture a few times and got the same problem, so im determined to learn from your good advice gents, Thanks again!!

[chopper5654]

is there a way we can post the photo with the curves adjusted, tony? i think some of us would like to see the results of what you described.

XR3, you would have to go into your user control panel, under image editing (i think) and click "yes" to allow tony to repost your image. i think it would help us as a learning tool to see your before and tony's after shots.

[tonydee]

Did feel a bit strange not including the result :-). I think I'll hit the sack, but will post tomorrow if XR3ste's enabled "IMAGE EDITING OK" in profile. Cheers, Tony

[XR3ste]

Have changed the option to allow edit, thanks again chaps!!!

[PlaidIsRad]

TonyDee, for someone just getting into processing, that was tremendously helpful. Much thanks. Consider it bookmarked...

[tonydee]

I hadn't saved the results last time, so redid the curves adjustment slightly differently...

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The result:

363245

Notes:

This approach is a little crude in that the entire picture is being affected by the new curve, while it's really only the lad's face and background that we want to work on. We're just lucky that they are so much brighter than anything else that there's room to drag them down in the curves adjustment without too much effect on the other parts of the image. A slightly more sophisticated approach is to simply make a selection around the area we want to modify before using curves, protecting the rest of the image. I would normally do that, but wanted to keep the steps simple.
At each pixel in an image, JPEG's record brightness of each of Red, Green and Blue using a number from 0 to 255. If I select most of the boy's face, GIMP's histogram shows the colour levels are around 248, with a standard deviation of 4.5. All that means is that there's only about 20 brightness levels differentiated across his face. By pulling the curves adjustment down more sharply, each of these input levels may end up 4 or 5 brightness levels apart, which can start to be a visible jump, making his face look like one of those contour maps with rings of successively darker colour. So, I had to try to find a balance between adding contrast and avoiding emphasising the gaps between the output brightness levels. RAW files record brightness levels using numbers from 0 to 4096 (12 bit) or 16383 (14 bit) - depends on the camera model - so there's much more freedom to stretch the contrast during post-processing.

[XR3ste]

A Masterclass, thanks so much for taking time to help me out, Much appreciated, thanks again!! :)