Histograms

Bill Pierce

Bill Pierce

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Face it; digital is exposure critical compared to negative film. Digital is like color transparency. Blow the highlights and they’re lost forever. And yet, if you avoid this digital pitfall by always leaning a little towards underexposure, contrasty scenes are going to have less shadow detail than they could. In spite of sophisticated TTL matrix metering, automatic exposure can sometimes still be improved upon by use of the human brain.

There are a lot of ways to maximize the quality of contrasty scenes; spot metering, bracketing and prayer worked well with film, and many folks use those techniques or HDR with digital. I just use the histogram provided by the camera along with manual exposure. More than any metering system I know, this digital-only wondertool can let us see exactly what a given exposure is doing in the highlight and shadow regions of our photograph. (The fact that the histogram often reflects what’s happening in the camera jpeg gives us a little safety cushion if we’re shooting raw.)

And yet I find that even though digital has given us this wonderful tool, not many people use it. It’s time to confess. Do you use this gift? Have you got anything better? Or do you think your camera knows more about exposure than you do?
 
In some ways I did prefer using my old Leica M3 without a meter or at least using only a hand held one. That way I could measure the ambient light and then just rely on my judgment from there on. I found it a very freeing way of shooting. In truth I still did rely on negative films inherent flexibility too. So yes I have (and do) rely on my brain and histogram when one is available.

Shooting digitally I do often shoot slightly to the left. I know perfectly well this is against "the rules" but my view is that "shoot to the right" is good advice only if you are in a studio and have absolute control over the shape of your histogram (studio lighting etc) before you press the shutter. Mostly this is not the case and in real life it will lead to grossly over exposed highlights. I prefer slightly under exposed shadows to blown highlights any day.
 
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The histogram is my most valued tool, both when shooting digitals (rare nowadays) and when digitally post-processing my film scans.


When shooting JPGs, I simply aim for a nicely-spread histogram - with EVF cameras I usually try to overlay a live histogram during shooting. Care is always taken not to blow any highlights, so if necessary I will under-expose and accept the noise-penalty.

With RAWs, I try to follow the ETTR guidelines to maximize detail - not to dissimilar, I'd say, to rating a film at slower than box speed and developing normally. Cleaner, more detailed shadows.

When post-processing scans, I try to make sure I don't clip highlights, and use it in conjunction with the Curves tool as a make-shift "Zone System", for example placing skin-tones at the luminance-levels I desire.
 
I've used Histograms with digital images for over 30 years. Punchcards to process a digital image.

"Clipping" the image was the term used for zero-value pixels and saturated pixels. Saturated pixels: "once it's saturated, the information is lost".

Low-contrast lenses on a Digital camera. That's the trick to compress the radiance of the scene to fit within the dynamic range of the sensor. I did a quick test of a Nikkor 5cm F1.4 against a Summarit 5cm F1.5. The Nikkor clips the image, the Summarit preserves the image.
 
I used it to great excess with digital. Chimp, chimp, chimp. I'd rather have an RGB histogram over the thumbnail if I had to pick. I agree 100% with your comments on exposure for digital. After a while I felt like I was in a straightjacket!
 
That's really about the only reason I use the screen on the back of the camera (other than setting menus, etc.)
Oh, sure I occasionally check an image for focus, framing, etc. But I'm most interested in the histogram. Those clipped highlights are image killers. It's silly to take chances when it is so easy to keep an eye on with the histogram.
 
On my Nikon D300 I use it, just not as often as I should.

On my Canon G11, they did it right, and I always use it. Basically on the G11 you can have the Histogram displayed while you're getting ready to take the photo, and make adjustments accordingly. It makes getting a good exposure, or the exposure you want a snap. I've also found that the G11 also makes a good lightmeter for my film cameras in low-light conditions (specifically I've used it to meter for my M6 TTL).
 
In fact, one of the few things Leica does better than other manufacturers in camera software is that (as far as I know) the digital Ms are the only cameras to display histograms of RAW data, not of the JPG previews.

Also, when zooming and panning the display, the histograms are updated to display only data from the currently displayed region of the image. Nice.

- N.
 
ndnik said:
In fact, one of the few things Leica does better than other manufacturers in camera software is that (as far as I know) the digital Ms are the only cameras to display histograms of RAW data, not of the JPG previews.

Also, when zooming and panning the display, the histograms are updated to display only data from the currently displayed region of the image. Nice.

- N.
Click to expand...

My D700 displays histograms for my raw images. Not sure about other cameras.
 
Bill Pierce said:
I just use the histogram provided by the camera along with manual exposure.
Click to expand...

Yes, I do exactly the same thing. I almost never use the meter. I guess the exposure with the DSLR in manual and use the histogram. Much better results than any auto-exposure scheme like A, P, S... Occasionally I'll use the spot meter or center-weighted meter, but always on M.
 
peterm1 said:
In some ways I did prefer using my old Leica M3 without a meter or at least using only a hand held one. That way I could measure the ambient light and then just rely on my judgment from there on. I found it a very freeing way of shooting. In truth I still did rely on negative films inherent flexibility too. So yes I have (and do) rely on my brain. Shooting digitally I do often shoot slightly to the left. I know perfectly well this is against "the rules" but my view is that "shoot to the right" is good advice only if you are in a studio and have absolute control over the shape of your histogram (studio lighting etc) before you press the shutter. Mostly this is not the case and in real life it will lead to grossly over exposed highlights. I prefer slightly under exposed shadows to blown highlights any day.
Click to expand...

With experience you can learn to bias the histogram to the right without blowing the highlights in most situations outside the studio. But I never shoot jpg, always RAW, which gives you much more latitude.
 
I have a plan to use it on a Nikon D40x/60 as my light meter. I am going back to estimating exposure and then looking at the histogram to see how bad/close/etc I am. If I need to reshoot. Perhaps expose a frame (not sure how to say it digitally) for exposure guidance and then get the shot.

I use it on my GRD III to insure I am not too hot. I do not like it during composition though.

B2 (;->
 
I use it all the time. The way highlights look on digital (the sudden jump to pure white rather than a subtle gradation) really bugs me. The only way I could manage it is with the histogram. I just wish the screen on my M8 was bigger.

fionn1.jpg


Marty
 
I do keep the histogram switched on much of the time. I position it close to the right edge, trying not to spill over the edge.

There are times when one is working too fast to be able to take the time to do all this. That's what Tri-X is for.
 
CCD and CMOS sensors are analog devices, and convert photons to an electric charge. This charge must be digitized, and goes through a preamp into an analog to digital converter. Linear preamps are generally used leading to the A/D.

I've used non-linear preamps between a detector and A/D with some custom circuits to increase the dynamic range of the system. I wonder when Digital cameras will start pushing the overall dynamic range of the system with some non-linear preamps to make it behave more like film.
 
I'm surprised that the higher end folks have not focused on this yet. Higher end being the MF folks and all. I think part of the problem is that the design point they were when initially designing stuff was the computer as output or perhaps Cibachrome. I saw some tricks when I was at a startup for putting multipliers in silicone rather than in software for speeding up transformations and all. Perhaps it is an issue with patents (the old double edge sword thing)? Have A/D chips improved as fast as CMOS/CCDs have? Speed of writing the image may force some concessions in design too. Some pros would be very happy to wait 10 seconds between images to get a wider range of response, others I suspect are quite happy.

B2
 
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