Using the Histogram

[Herk_Man]

I did a search for "Histogram" on the photography tips and techniques and didn't find a thread dedicated to a discussion of this feature of a camera. My PnS has the ability to display the histogram while shooting.

Am wondering if this feature is useful while shooting underwater, and if so, what I should be looking for. I think the basics are that you want the peak of the white to be near the middle of the histogram.

And how do you read the green part?

Thanks

HM

 

[strobeless]

I did a search for "Histogram" on the photography tips and techniques and didn't find a thread dedicated to a discussion of this feature of a camera. My PnS has the ability to display the histogram while shooting.

Am wondering if this feature is useful while shooting underwater, and if so, what I should be looking for. I think the basics are that you want the peak of the white to be near the middle of the histogram.

And how do you read the green part?

Thanks

HM

The histogram can give you clues as to your exposure.

If all the info is crammed to the right with the left side being blank, then you are over exposed. Flip this scenario around and you are underexposed. The best possible histogram is actually a thick, high, even spread, reading solid all the way across from left to right, with relatively as few peaks and valleys as possible.

Not sure what you mean by "the green part."

 

[PatW]

I don't know about your camera, but most histograms show the white light spectrum. As you know, you "want" your histogram to have a peak in the middle of the screen with it tailing off on both margins. That happy situation is not always possible.

As for the "green", many cameras will display the individual color histograms. The colors in digital photography are red, blue and green. So you might be talking about the green histogram. In underwater photography, red light is absorbed pretty rapidly by water. So a red histogram will be pretty much gone at unless you are at pretty shallow depths. That is why most underwater photography is driven by flash units. The flashes restore the red light and the brilliant colors you get in many marine environments.

 

[M_Bipartitus]

This website might help your understanding a little. It isn't specific to underwater, but has examples of photos and their histograms.

Basically you don't want to avoid peaks at either end and the stuff in between depends on your subject and the style of photo you are trying to achieve.

 

[strobeless]

Where I'm coming from is, I want to capture as high as possible and as straight and even all the way across, that way I can clip the ends and/or pump the mids to create my own peak for the final. The more info you have to work with the better off you are. But I guess I just assume that people are going to rework their levels.

In an underwater situation, most of the time you have the reds pushed to the left and the greens and blues pushed to the right. When viewing the histogram on a camera you mostly likely are seeing the composite histo, so with the G & B being on one side and R being on the other side the composite looks somewhat full all the way across. This gives a good amount of info to work with. After reworking you levels properly, you will have a nice peak in the center and your info will be clipped looking slightly spread out (more spaces slightly showing).

If your capture composite has pronounced peaks at each end and very low in the center, then you are not capturing enough info in each R G and B and you will have a tough time reworking you levels to any satisfactory result.

Unless you shoot with a strobe you will hard pressed to get a seriously full histo underwater. (But then again, I go strobeless.)

 

[M_Bipartitus]

I agree that this works for some situations, but 1) not everyone uses RAW, so there is less flexibility to post-process, 2) you don't always have the option to adjust the contrast of you scene, and 3) sometimes you know what you want the final photo to look like, so you shoot it that way. For example, If I have a black fish in front of a light coral, I'd be hard pressed to get a constant histogram throughout the range. I could, however choose to have a better exposure on one or the other and the histogram will reflect that.

 

[herman]

One point here, some times you DO want a lot on the left side. Remember black and underexposure are more or less the same thing. I often shoot with my subject with a black backgound so I will have and want a lot of the far left hand side filled, how much depends on the amount of backgound I have in the photo. Conversely sometimes a light background or a white subject will push the curve quite a bit to the right. What your curve looks like has as a lot to do with the shade of the objects in the frame. A photo of a white sign with black letters would have a large portion of the left hand side (but before the overexposed line) of the histogram filled, nothing in the middle and a more in the far right "underexposed" section. How much in the right side will depend on the amout of black area the sign has. Put a gray section in the sign and you would add a spike somewhere in the middle of the histogram.

 

[gypsyjim]

I am not an accomplished UW photog, or any kind of photog, for that matter. I did discover for myself, after taking an UW seminar on Photoshop at BTS, that re-balancing the Histogram in PS works wonders for improving the quality of many of my pictures. It is often the only adjustment I use, in that this adjustment "spreads out" a shortened or abbreviated histogram, even pulling a good image from several night dive photos so under exposed I thought there was no image at all!

 

[CompuDude]

There's a lot of good info here on the the topic of histograms (and many others):

Histograms|Underwater Photography Guide

 

[strobeless]

I am not an accomplished UW photog, or any kind of photog, for that matter. I did discover for myself, after taking an UW seminar on Photoshop at BTS, that re-balancing the Histogram in PS works wonders for improving the quality of many of my pictures. It is often the only adjustment I use, in that this adjustment "spreads out" a shortened or abbreviated histogram, even pulling a good image from several night dive photos so under exposed I thought there was no image at all!

Yes, that's more towards where I'm going with this. On dry land you will capture more information shooting an optimized histogram and have excellent results.

But when underwater, especially without a strobe, I approach image capture from a Drum Scanning point of view rather than a Photography point of view.

I treat the subject as if I'm scanning an old faded color photo. So in that situation, I will get less information to work with scanning through an optimized histogram and I'll get more information to work with in my histogram by capturing a large "flat" scan.

I apply that mode of thinking when shooting underwater, especially since I don't like to carry a strobe, and the results are very nice.

Here is an example. I have sort of broad exposure that's capturing both shadow detail and highlight detail and nice flat histo. I could tighten up the exposure to have a much better contrast and detail with an optimized histo, but the photo, nice as it would be, would still be green. At that point I would move to photoshop to balance the levels to bring the natural colors out, but I would be short on information and the color would get noisy and fall apart before approaching something nice.