Histogram advice

Reading a comment to a photo on another site this comment was made

Otherwise, unless you are deliberately going for low-key, you should always make sure some pixels in the frame reach the 255 level(Histogram reaches the right hand side at the 255 level).

Is that good advice?

Mike

Not really. A value of 255 is pure white, in other words blown out highlight.

The object of the exercise of photography is to produce striking images and many of these do not obey such technical constraints.

I think there is a lot of misunderstanding as to what the histogram does and although it's a useful tool I very rarely look at it. If the image looks right, then it is right, regardless of the histogram.

This is a example.
[IMG]http://i486.photobucket.com/albums/rr227/TTKPhotography_2009/Histogram.jpg[/IMG]

Left:-Under Exposed, Middle:-About Right, Right:- Over Exposed.

Sorry it's small

You might learn a lot about the histogram from here.

You're right, but only up to a point. What needs to be asked is whether or not a shot is exposed correctly to show what the photographer wants to be shown.

For example, let's take a sunset with trees in front. This could be exposed to show a dark brooding image, a bright subset with trees in silhouette or to show detail in the trees letting the sky become very light. Depending on what was wanted from the shot all three exposures could be "correct".

If the key issue is general average snapshots then the situation is different and any camera on matrix metering mode will try to produce something that gives an average sort of image.

There are whole books on the subject of exposure....

Ya know what? I reckon that's about the best advice I've ever read about exposure!

Graham (who's switched off the histogram!)

In summary I think the consensus is that the guy giving the advice wasn't right - he appears a rather an arrogant chap.

I know what John means in a way if looks like you wanted it to be then it is right but I usually do look at the histogram to make sure nothing dumb is going on that will need attention in post processing.

regarding TTK's examples - is the black camera shot actually under exposed or simply an image with lots of black?

Of course my man would have you adjust the exposure to have something right up the white at 255.

Thanks guys.

Mike

There is actually a valid argument for 'exposing to the right' and that is to preserve as much shadow detail as is possible without blowing out whites/highlights. Exposure can always be reduced in post-processing to make the image look more like what was originally required.

I read that too - I read it as a way of exploiting the additional dynamic range at the right of the histogram apparently. I tried it and found it to be a bit awkward to use and really didn't seem to make that much difference.

YMMV as they say!

Mike

Exposing "to the right" can be fine in many cases, but sometimes can result in washed-out images that no amount of post-processing can fix. At least that's my experience with Silkypix - my favourite RAW program. This is even when no highlights were blown.

I read an article encouring the technique shortly before going on holiday this year and I thought I'd give it a go. Frankly, it ruined quite a few of my photos.

Not dissimilar to my experience - a technique to use with caution I think.

Mike

I just make sure the histogram doesn't go beyond the right hand edge and not worry too much about getting right up to the right hand edge. If you are shooting RAW (which you are), there are plenty of levels left to play with. I then have room to brighten, darken, or whatever the image a great deal in the software. Once the histogram has gone past the right hand edge, its blown and there is nothing left to do.

As to it "looking correct" in the preview, actually I disagree. Often pictures which are mainly dark but with some bright parts will look awfully under-exposed on the preview but post processing (e.g. the shadow highlight tool in CS3) will pull masses of lovely detail out of the shadows. Also, judging the exposure on the LCD is greatly affected by how bright you have the screen set and the ambient light. I have long abandoned trying to judge if the exposure is "correct" by looking at the image and just glance at the histogram.

On a related note, I have been wandering around New York for a couple of days. We had a couple of beautiful clear blue sunny days but the range of EVs from the sky to street level was so extreme that it was well out of the dynamic range of the sensor. I did think about HDR but (a) the lack of tripod here and (b) the traffic and people rather counts that out. It was easier the day it snowed!

Best wishes, Kris.

I would disagree too. I was referring to the final image looking right, regardless of anything else. The image looks right when it conveys what the photographer intended.

You certainly can't properly judge exposure from the camera's screen.

Sorry, I misunderstood you I am glad we agree!

Best wishes, Kris.

I gather (from the martin Evening cs3 book) that the on camera histogram is often based on jpeg capture only. If you are shooting in RAW it will not provide an accurate guide to the true potential of the image you have captured.