Histograms

[TheGoofster]

I've been doing some study recently on this built-in feature that most DSLR cameras have (another feature that I never dealt with using my old SLR camera).
At first I didn't really understand very well what I was reading, but the more I started studying it, the more it started making sense, and the more important is seems to be to better understand and best use the camera.

So, I was wondering how much histograms are used by the photographers here on the DIS? If you do use them regularly, what do you use them for the most?
From what I understand, they have different uses (tonal range, contrast, color range, etc...). Do you find yourself using them for one specific reason, or do you try to take advantage of all the uses of them?

This is something that I hope to get better at (and understand much better) with lots of use.

 

[disneyboy2003]

I must admit that I should probably use histograms a lot more than I'm currently doing. I think I put too much faith into the image on the LCD screen.

I tend to do a lot of photography at night or in dark theaters. So the histogram interprets all that black space and always tells me that my pictures are too dark. Not very helpful.

For me, the histogram is most helpful during the day or in a better-lit situation. After taking a picture and noticing that the picture is "too dark", you never know whether the picture is "too dark" (1) because of underexposure, (2) because you've set the brightness of the LCD screen too low, or (3) because it's extremely bright outside, making it harder to view the relatively-darker LCD screen.

That's where the histogram can help make sure you've got the proper exposure to your picture.

Actually, with digital cameras, you're supposed to slightly overexpose your pictures (everything in the histogram moves to the right) so that you capture the most amount of luminance data (is that correct?). And then in post-processing, you can bring the image back down to the correct exposure. There's a lot of technical reasons why this works, but I'll let someone else explain.

 

[AndrewWG]

Histogram? Yeah, I think my camera has one of those. Honestly, I find that I can never take a "perfect" picture if I rely on looking at that. I am sure it has it's uses but if you rely on that to get the perfect shot, you will most likely be taking several more pics than you really need to since they can be fixed in post processing. As disneyboy said, it depends so much on the situation and surroundings of your photo, it just seems useless alot of the time. Just my experience anyways. I have no idea what button to push to see the histogram on my camera anymore.

 

[boBQuincy]

Looking at things the other way, the image on the LCD is mainly useful to me only to see if someone walked in front of the camera while I was taking the picture. The histogram (and the blinking highlights) is what I use to check exposure. When I was photographing "A Midsummer Night's Dream" many of the scenes were pretty dark. The image on the LCD looked like I had nothing good but the histogram showed a fair amount of data in the middle range (along with a lot on the left side) so I knew I had something to work with.

The three color histogram is even better, we can see if one channel is washed out. Of course keeping the histogram on the LCD means the image area is very small but that's ok, it's the histogram that I really pay attention to. If the histogram does not look good or if the highlights are blinking I usually adjust exposure compensation and try again.
Or just fire off a HDR set!

 

[Groucho]

I had my K20D set to show a histogram on the quick review, but never turned that on with the K-7 as the quick review is not long enough to look at the photo and check the histogram.

So, if I want to see it, I cycle through the view options. However, I rarely look at it too closely when out shooting; I mainly check for general over or underexposure. Knowing that one particular color channel is blown out is fine but honestly, what are you going to do about it? Unless you are carrying around a set of color filters and don't mind slapping them on for very specific situations, I'm not really sure what help it is in-camera.

Now, when post-processing in Lightroom, I do keep a pretty close eye on the histogram. If I'm working on a photo with low constrast (due to a particular lens or shooting through a window or whatnot), I will often bring up the blacks in order to spread out the histogram more, usually until the graph stretches almost all the way to the left. This is a nice way of effectively boosting the constrast and bringing in a bit more "pop". You can also dial back specific colors based on the histogram's color spread.

IMHO you can't be a slave to it, though - some photos leave a bit of blank room on the right and the initial reaction is to brighten them up to fill in that space, but some photos look better more towards the middle. Like everything else, it's a tool not a rule.

 

[pointandshoot]

Camera LCDs and over 40 eyes do not play well together for me.

Use it often to check for blown out highlights and loss of shadow detail. Basically glance at the edges. Also try to shoot towards a brighter end since it is easier to pull back detail in PP.

Other than that, I use it to generally see where the image is going. No such thing as a good or bad histogram in my opinion. It helps me see if what I intended to shoot in terms of exposure is what I accomplished. A data point for me when I cannot tell from an LCD display of the image. A bit easier to read when in bright daylight.

Chuck

 

[wenrob]

When I "chimp" I'm usually looking at the histogram. It depends on the shooting conditions but I generally try make sure nothing is pushing up against the sides and I try to just "kiss" the right side. I personally think the histogram is essential, it really helped me to understand what the heck I was or wasn't doing.

 

[seashoreCM]

All I look for is a mountain against the left side indicating buried shadows, or a mountain against the right side indicating blown highlights. Don't have time to do much more. Often enough I find mountains against both sides in which case I might want to just take more shots with different exposures (bracketing) except I don't know how to merge the best parts of each of them using Photoshop or whatever.

Don't forget, if you are using an automatic camera and you adjust the exposure compensation, you must frame the next shot exactly the same way. Otherwise the different subject matter in the next shot will make the camera choose different settings automatically and then apply the exposure compensation. This produces and apples to oranges i.e. useless comparison with the first picture.

I don't look at histograms as often as I would like because on my camera it takes so many button pushes (like more than two with having to peer at the menu in between) to get to the histogram. Wish cameras had some customizable buttons for the features you use most often, including exposure compensation.

My camera lets me spot meter (point the camera at something to set the automatic exposure) in advance, push the button halfway, then frame the subject, and shoot. So I can bracket exposure to some extent without having to proactively adjust anything else.

When I do postprocessing (which is actualy rarely) I don't use histograms or color charts to white balance charts. I just examine the picture itself. But on some postprocessors I may need to go to the charts to access the adjustments.

Digital camera hints: http://www.cockam.com/digicam.htm

 

[RBennett]

Is there a tip/book/explanation on more info re: histograms? I'll be honest, I've been shooting now for a little over 2 years and I have yet to utilize this. I generally shoot out of "auto" mode so that I can learn more about what I want and what effect it has, so I try to keep it exposed to 0.0 (or whatever I think the shot needs.) But is there a better explanation out there?

 

[disneyboy2003]

Is there a tip/book/explanation on more info re: histograms? I'll be honest, I've been shooting now for a little over 2 years and I have yet to utilize this. I generally shoot out of "auto" mode so that I can learn more about what I want and what effect it has, so I try to keep it exposed to 0.0 (or whatever I think the shot needs.) But is there a better explanation out there?

I think any good Intro to Digital Photography book will already have a section on histograms and how to interpret them. You can probably stop by your local bookstore / library and just read up on that particular topic.

Other good online sources include:

• Simple: http://www.digital-slr-guide.com/how-to-read-a-histogram.html
• Intermed - Advanced: Cambridge in Colour - Understanding Camera Histograms
• Intermed - Advanced: Luminous Landscape - Understanding Histograms

In general, the histogram can tell you whether your picture is properly exposed, underexposed, or overexposed. (it can tell you other stuff, too, but exposure is probably the easiest thing) If your picture is underexposed, as determined by the histogram, you can then use that information to correct your exposure (ex. adding (+) exposure compensation, decrease shutter speed, increase aperture, bump up ISO, etc).

If you're just shooting "Auto", however, can you tell the camera to increase / decrease the exposure? For example, you take a picture in "Auto" mode and the histogram tells you that the picture is underexposed, what can you do next?

 

[jann1033]

in the field, i use it pretty much to check the edges to beware of huge crammed up to the edge mountains but since i read that with most cameras they are set up for jpg and i shoot raw i don't figure they are the be all or end all. i use them all the time in lightroom though.

as far as the auto goes, i think that is where i would use the p mode in canon. it lets you set things like +/-exposure etc but sets the shutter and aperture( i think i don't really ever use it but i think that is what the manual said )

 

[MarkBarbieri]

I had my K20D set to show a histogram on the quick review, but never turned that on with the K-7 as the quick review is not long enough to look at the photo and check the histogram.

I adjust my picture review time based on how and where I'm shooting. If I'm running and gunning (typical soccer game), I keep it short because I'm just going to glance at it. If I'm out on a photo shoot, I set it much longer so that I can take my time to review it. If I'm shooting in a dark theater (like Nemo or FotLK), I turn it off.

Knowing that one particular color channel is blown out is fine but honestly, what are you going to do about it?

I usually only pay attention to the RGB histogram when I'm shooting colorful (especially saturated) stuff. A common example is with flowers. If I shoot a red flower and the red channel is blown out, I back off my overall exposure. The other case that it helps me is when shooting people with garishly saturated clothes. The BW histogram looks OK, but the RGB shows that you've got a problem. The only fix is adjusting the overall exposure.[/quote]

Now, when post-processing in Lightroom, I do keep a pretty close eye on the histogram. If I'm working on a photo with low constrast (due to a particular lens or shooting through a window or whatnot), I will often bring up the blacks in order to spread out the histogram more, usually until the graph stretches almost all the way to the left. This is a nice way of effectively boosting the constrast and bringing in a bit more "pop". You can also dial back specific colors based on the histogram's color spread.

I definitely concur. I frequently spread my histogram (by adjusting black and white points). I do this even on a well shot scene that just happens to have low contrast.[/quote]

in the field, i use it pretty much to check the edges to beware of huge crammed up to the edge mountains but since i read that with most cameras they are set up for jpg and i shoot raw i don't figure they are the be all or end all. i use them all the time in lightroom though.

You are correct, at least for Canon. The histogram reflects the picture after any jpg adjustments have been made. For that reason, if you shoot RAW, I suggest keeping your saturation low. That avoids having your histogram tell you that you've blown out a color when you really haven't. I've also heard that you should try to keep your white balance accurate (even though you can easily change it in post) when shooting RAW because an extreme variance can cause a noticeable luminance shift for some color channels and mess with your histogram.

 

[TheGoofster]

Thanks everyone for you replies. I have a ton of respect for the many different photographers on this board, and I like to hear what you have to say about different subjects.
It is interesting to hear the different opinions about the importance / usefulness of histograms. This is something that I think I need to spend more time studying.
I do appreciate all the responses, it definitely gives me something more to go on.

 

[mrodgers]

I never use the histogram on the camera. The only time I "chimp" on the LCD screen is when the kids are bothering me with "let me see.... let me see...." after every shot. That's the only time I see the image on the screen.

I merely adjust levels in Photoshop, thus I see the histogram there. Rarely do I see it on the extreme ends. I mostly have to pull the white and black points in to spread out the histogram.

The histogram can be a great learning tool. But I've found that once you know your camera in detail and how it shoots (after learning about exposure of course), you shouldn't need the histogram. You will know how the camera will expose the image.

Perhaps it would be different with a dSLR, I don't know as I don't have one. I have a superzoom that is 2 years old and use it 90% of the time in manual. I learned about what the histogram was long after I learned about exposure and learned my camera enough that I knew how the shot would come out like within the limits of the camera itself.