Histogram help

I will be back on Guam for a few days and once again I will put the S2 through some more testing. I will try underexposing the background (water) in hopes that that will give me nicer blues. I would like to use the histogram feature while underwater so that I can see the results without relying on the camera monitor brightness.

I hope that a few of you knowledgeable types can give me a crash course in what type of histogram I should be trying to achieve. A few screen shots showing "good" and "bad" would be quite helpful.

Again I will be trying to underexpose, therefore please take this in consideration.

Thanks in Advance

Chris

Hi Chris,

The histogram will depend on what kind of subject you are shooting. To give you an example, photos with a lot of the pixels in the highlight areas (high-key) will look significantly different than a shot that has a very dark background with most the pixels in the shadows to midtones (low key). These are some examples from Photoshop histograms, but the same rules apply to the histogram you see on your camera LCD.

No matter what, you want to avoid blowing out your highlights, so made sure your histogram doesn't run off the right side of the scale. A histogram that doesn't reach all the way to the right side is not necessarily bad and gives you a little room for correction in Photoshop if necessary. This was typically the way I used to scan slides for prepress, a little flat, then make the final adjustments in Photoshop. If you're shooting for perfect histogram, it would not crop off any pixels in the highlights or shadows, but this isn't always possible, especially if you've got any sun in the shot. I'll see if I can dig up a few bluewater histograms also.

Does the S2 allow you to view different color channel histograms? I shoot with the D100, so only have one combined histogram to view when shooting.

Hope this helps.

Bonnie

You don't want this...

A histogram like this will be better, but depends on your subject.

Bonnie

Thanks for the reply. I will try to keep the histogram from reaching the right side of the scale if not just a bit more left of it. I have to actually check the camera and see what it produces.

My main goal is to reduce the strong cyan cast that ends up replacing what is normally bright blue (in film shots). the (good) blue water shot in your post adds a lot of detail but the brighter areas still appear greenish. This is exactly what I am getting unless the shot as been severely underexposed, The underexposed shots preserve the lighter blues, but I pay the price by the loss of too much shadow detail. Robbing Peter to pay Paul!

What little close up shooting I did do, turned out very nice, but I make my money shooting divers that visit Guam on holiday most of which include lots of blue water in the background.

Thanks again for the help.

PS: I checked out your site, and I am very interested in some of those workflow courses. Nice and affordable!

Kindest Regards

Chris

Generally speaking, a histogram that runs off the right is a ruined shot. I check each shot and if I see the histogram touch the right I shoot it again. Avoiding that situation is mandatory (at least on the D100).

Level of exposure will not effect color in a digital camera as it can in film. If you desire to avoid cyan water in the type of shot in Bonnie's example, you will need to correct it using a filter or PS. Underexposing it will just give you dark cyan. The camera can only record what its lens sees, and in this case it sees cyan water.

I believe that (some) rules of exposure are different for digital and film. With film, the level of exposure effects color saturation and color balance. With digital, it only effects SNR. Exposing strobe vs. ambient works the same way, but with digital there is no advantage to overall underexposure.

Thanks Craig

You mean the CCD records cyan, My eyes see blue

Filters would work for silhouettes but I think they would have and adverse affect on the strobe illuminated subject in the foreground (unless you added a filter to the strobe to compensate for the lens filter, ).

I may just have to re evaluate how I compose the shots, I.E. taking the sun out of the shot. I will try all options.

Digital makes this cheap!

Chris

You can get away with unfiltered strobes provided the subject is monochromatic (like sharks). Reef scenics are more problematic.

I wanted to experiment further with this but had no wide angle opportunities on my last trip. In any event, I wasn't trying to turn this into a filter advocacy thread. I just wanted to mention that digital does shift color with exposure as film sometimes can.

It's interesting to read up on how brightness and saturation interact and how that differs with hue. I'd provide a link but I no longer have one. Still, the eye is at once amazingly versatile and incredibly inaccurate.

The histograms posted are not ideal in terms of obtaining the highest possible final image quality - they show what the histograms of the final adjusted images should look like, but do not show the types of histograms you want at the capture stage.

You want to see a histogram that has content as far over to the right as you can get without over-exposing. This will provide the maximum amount of shadow detail. This doesn't matter so much if you are going to be using the image pretty much as shot,

but if you plan on doing curves adjustment, or various forms of dodging and burning,

you want there to be as much shadow detail as possible available for you to "bring out".

This will produce an image which appears over-exposed when viewed in the lcd, and when imported without adjustment. However, when you adjust the exposure, you will

end up with an image that has more shadow detail present then if you had taken the

"proper appearing" exposure at first.

The problem you had with the weird water colors came from over-exposing one of the color channels. I don't have the same camera as you, so I can't tell you exactly what the histogram will look like as you approach overexposure in the blue channel. What I would suggest is setting up something blue-ish to take a picture of on land and watch what your histogram and over-exposure indicators look like as you approach over-exposure.

Really, I thought the histograms looked OK except the one intended to be bad. The first three were clearly corrected histograms.

At first I didn't believe the last example was overexposed in blue. Sure enough, it is (and green may be as well). As a result, the image may well be more cyan than it should be.

Anyone know photoshop's luminosity model? Green contributes far less than I expected.

I'm headed to Guadalupe tonight for some Great White shark diving over the next five days. I'll do some experimenting with the D100 histogram. I believe there will be a number of S2 cameras on board too. I'm interested to see how the histogram as it appears through the LCD compares to those in Photoshop and how they both represent the resulting images. Report in a week.

I recently read a user report on the 14n. The reviewer said that the 14n should be shot to expose shadows rather than highlights and that it took getting used to. That suggests to me that the 14n's histogram function does not work as you'd expect. Of course, the reviewer might simply have been wrong, but a careful inspection of the different cameras' builtin histograms might prove interesting.

I may be only to get in about 4 dives or so but I will try to do as much experimenting as possible. This time I remembered to pack the RAW converter software

I will be back online in about 24 hours from my home on Guam. I will try to post some of the shots while I am still on Guam, hopefully with your assistance I will have more success than the first attempt.

Getting ready for the long drive to Tokyo. The drive is twice as long as the flight!

Again Thanks for the detailed help

Chris

I recently read a user report on the 14n.

Craig - Do you have the link to that report?

You want to see a histogram that has content as far over to the right as you can get without over-exposing. This will provide the maximum amount of shadow detail.

This is my understanding also. But as mentioned you are flirting with overexposure blowouts. Also if using this technique you need to shoot in RAW and optimise the image in a RAW conversion program.

Here is a good (despite coming from Luminous Landscape Craig B) ) article on this issue:

http://www.luminous-landscape.com/tutorial...ose-right.shtml

You mean the CCD records cyan, My eyes see blue

This to my way of thinking may be more than a throwaway line.

Where I shoot the background water is usually green. Some slide films, notably Fuji's, make it bluer which makes it look nicer to the eye; a little exotic.

Are you all sure that it's the CCD that lies and not the "Disneychrome" we are used to shooting?

I found this comment on the 14n at the DPReview forum. It turns out it's not a review or report. Just an initial impression from a new owner. There is a response and mention of some previous comment or thread saying the same thing. The claim is that you can (and should) overexpose with the 14n. I doubt it. There has to be more to it than this.

http://forums.dpreview.com/forums/read.asp...message=6490896

Well, I finally had a chance to do a little bit of experimenting with blue water histograms. Here is what I found when comparing histograms from the D100 and S2 to Photoshop.

The Guadalue trip was nothing short of amazing. I'd highly recommend it to anyone who wants to get in the water with Great Whites.

Thanks for the link and article Bonnie

Great job, Bonnie. It's good to know the relationship between PS histograms and the in-camera ones. I take it that you prefer the blinking highlights to check for overexposure or was the consensus on the trip to trust traditional film exposure rules? In any event, your advice to not run the exposure up to the righthand limit looks wise at this point.

On a separate issue, the 14n redefines the right side of the in-camera histogram to include a 2-stop "keepout" zone to avoid highlight clipping. The RAW conversion tools don't show this region (although it's there), making the 14n even more infuriating to figure out the correct exposure!

Thanks Bonnie

Great article

Quite detailed and easy to understand, even for a digital beginner like myself.

Chris