Histograms

[Soothsayerman]

I don't anymore but I used to chimp a lot. I just understood after a while where I could trust my eval metering and where I could not and what would give me a proper exposure. Where I can't trust it, I spot meter zones or I will use the histogram. The histogram is a beautiful thing.

 

[charjohncarter]

I use it, but when I scan negatives and when I do the final post processing. If I take a digital image with one of my DSLRs it is at christmas so I don't care that much.

 

[shimokita]

Q: Do you use this gift?

I use to use this when I got my 30D and 5DII, and it helped, but recently I don't use it as much. I rely more on the image and the feeling I get from the image as displayed on the back screen (5DII). Particularly when I shoot manual mode for "special" situations like pre-dawn or sunset. I have trouble to interpret the histogram in these situations and I am not looking for a "standard/normal" exposure.

Q: Have you got anything better?

The comments and link by "mtargz" was most interesting from a technical aspect and I have to study it a little more in detail. To be honest I am 80%/20% a film/digital person so histograms are not that importaint on a daily basis... but for that 20% it's evolving as mentioned above.

Q: Or do you think your camera knows more about exposure than you do?

In some ways yes... I do rely on the metering system of the specific cameras (for the first shot), but then normally move to manual mode. If I am shooting with flash then the camera has a larger "say" in how I shoot. But it's mostly on camera flash back stage or in a group type of setting.

Note: I don't have the over exposure areas hightlighted.... it's mostly a feeling of what the "test shot" captured.

Casey

 

[Sonnar Brian]

PKR- With the work we did, a Pixel that received 0 photons would be the noise floor. The A/D would get some value because of noise, we would store just that and leave any filtering to software. These days- camera manufacturers are putting the signal processing into the firmware, and I suspect the noise floor gets subtracted out.

Basic rule-of-thumb, the more bits of accuracy in an A/D convertor, the more time required to do the conversion. Settling times take longer with longer bit-length. Write-times and memory requirements go up with longer samples. 16-bit seems to be the norm for RAW these days, but some cameras such as Pentax are equipped with 22-bit A/D convertors. This allows 64times larger values. A non-linear preamp would "squeeze" the analog value into a 16-bitA/D, with a shape to the curve that mimicked film.

My particular project squeezed an analog signal into 12-bits using a Log preamp that otherwise would have required a 22-bit A/D. The latter would not work because those available required too long to settle.

 

[sacundim]

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.

My D700 displays histograms for my raw images. Not sure about other cameras.

I'm not sure you understood ndik's point. Every RAW capable camera I've seen shows a histogram for RAW shots, but this histogram isn't calculated directly from the RAW data, but rather, from the processed thumbnail that's embedded in it. So, for example, the color channels in the histogram have been shifted for white balance, and in-camera constrast curves have been applied.

 

[sacundim]

My Panasonic Micro Four Thirds cameras have live histogram right in the viewfinder. The display could be better, but still, it's the most awesome camera meter ever—you turn the exposure controls and the camera instantly shows you an approximation of how the shot's histogram is going to end up.

 

[mrmeadows]

Isn't it often a whole lot faster to use auto-exposure-bracket than to spend time chimping the histogram to avoid blown highlights?

---- Mike

 

[Bill Pierce]

Isn't it often a whole lot faster to use auto-exposure-bracket than to spend time chimping the histogram to avoid blown highlights?

---- Mike

Not when the specific moment is important. Say, the street, portraiture, sports, a whole bunch of things where it makes more sense to set the exposure and wait for the moment.

 

[Peter Klein]

I use the histogram all the time. With the M8, if I see a likely scene and it's got a large contrast range, I'll take a dummy frame and chimp the histogram to be sure I've got the exposure right. If needed, I switch to manual and set things how I want them.

With the Panasonic G1 it's even easier. The histogram is live, so I don't even need a dummy shot.

But you don't have to "meter" or chimp every shot. Once you know the right manual exposure, you can shoot away until conditions change. That's why those exposure guides inside the film boxes worked. 🙂

 

[rogerzilla]

I use it with film. Scan the film, apply a curves adjustment if necessary because film was made to be printed onto paper with its own sensitometric response, not scanned (Neopan Acros needs an r-shaped curve with my Reflecta scanner) and then adjust the brightness and contrast to fill the histogram window. This usually gets the image pretty close to how it looked and I know I've squeezed the whole tonal range out of the negative. At this point it's sometimes necessary to increase the contrast a bit more and sacrifice either the highlights (often boring bits of sky) or the shadows to get the rest of it looking good. You'd do the same by choosing a particular grade of printing paper and doing a test strip.