How do I correct exposure using the histogram?

[FlipsidE]

Ok, so I've read about and think I understand how to read histograms. But, what I don't understand is how to make the exposure corrections based on what I'm seeing. It seems that the histogram tutorials I've read only teach you how to read the histogram and not how to make exposure corrections based on what the histogram is telling you.

If I can tell that the shot is going to be underexposed, how would I correct that? If I can tell the shot is going to be blown out, how do I correct that?

Thanks in advance

FlipsidE

[scottbergerphoto]

If the histogram is to the left, add exposure(slower shutter, wider f stop), If the histogram is too far to the right, decrease exposure (faster shutter, narrower f stop).
Scott

[coarphoto]

this is going to be a very simple answer because i find that if you take a little information at a time you will be more able to use it and build on it so here goes.......

When you look at your histogram if all of the information is stacked up on the right side of it your highlights will be too bright therefore you should either colse down your f stop or speed up your shutter speed. do this until you see the information creep back to the center of the histogram. likewise do just the oppisite if your histogram shows all of the informatrion on the left side of the histogram...

Again this is a very generalized overview practice this and your exposures will improve i promise.

[PacAce]

Adding to what Scott has already said, if the histogram is to the left (under exposed) and you want to move it more to the right, turn the main dial at the back of the camera clockwise for positive exposure compensation. Each segment of the histogram is roughly one stop so you can use that to gauge how much EC you should apply.

Conversely, if the histogram is too much to the right (over exposed), turn the dial counterclockwise for negative exposure compensation. Here you're have to play it more by ear since you can't tell from the histogram by how much you're over if it's blown.

NOTE: the above is applicable only if you are shooting in AE mode. In M mode, the same idea applies but you have to adjust the shutter and/or the aperture manually.

[trustwoody]

Is there a perfect histogram? Or is there a look to a histogram that will cause the least amount of post processing?

[Cadenza]

Hence another advantage of having a live LCD
preview in DSLRs. Canon could fashion an
AUTO "shoot to the right" mode, since with the
live LCD Canon engineers could easily generate
an exposure/aperture algorhythm based on
live histogram readings.

[PacAce]

Is there a perfect histogram? Or is there a look to a histogram that will cause the least amount of post processing?
A histogram is just a graphical representation of the different levels of light in a given scene as taken by the camera and nothing more. It can neither be right or wrong, perfect or imperfect. It is just another tool you can use to determine how your picture was exposed. It is up to you to read it, interpret it's meaning in relationship what you are striving for in the picture and take it from there.

[FlipsidE]

PacAce,

I use a DRebel...there isn't a dial on the back of the cam for EC. I know it has EC ability, but I don't think it's done via a dial on the back. I'll have to look into it.

And to everyone else, thanks for all the advice so far!! :)

FlipsidE

[mdr]

Note that a picture with a lot of dark or a lot of light areas will need to be skewed to the left or the right to show the correct exposure. Therefore, the oposite of above suggestions will need to be carried out to skew the histogram to one side in for example snow scenes.

[ijohnson]

There are some great websites about reading histograms. I don't know any of them off hand but I am sure that someone here will come to the rescue. Otherwise, just search for "reading a histogram".

I use exposure compensation very frequently, based on the histogram reading from the last exposure, however, with my 10d, I have a tendency to go +1/3 for most shots. It seems to work well, unless I am using my 70-200 f2.8. It won't have it. It says "don't adjust for me, I am perfect". All the other lenses need the extra 1/3 in my opinion.

[Jonny]

If the histogram is to the left, add exposure(slower shutter, wider f stop), If the histogram is too far to the right, decrease exposure (faster shutter, narrower f stop).
Scott

Is that how you would do it? Or would you just use the EC function?

[FlipsidE]

There are some great websites about reading histograms. I don't know any of them off hand but I am sure that someone here will come to the rescue. Otherwise, just search for "reading a histogram".

You are correct. There are quite a few websites out there on how to read a histogram, and they seem to do quite a good job on teaching someone how to read a histogram. I am feeling more comfortable reading histograms now. What I'm still not comfortable with (but am learning a ton in this thread) is correcting the exposure based on what I read from the histogram.

FlipsidE

[NGrinerPhoto]

take black paper, a gray card and white paper in that order and make an exposure card. when you take a photo of it and have proper exposure, you will see a spike in middle of the left, middle of the center and middle of the right.

-nick

[Jonny]

What I'm still not comfortable with (but am learning a ton in this thread) is correcting the exposure based on what I read from the histogram.


FlipsidE

I used to have a 300D but i have forgotten so much about it since i got the 20D!!
IIRC i used to shoot a pic and look at the histogram. If the histogram was biased towards the left it was indicating a 'dark' shot and i would adjust the EC to +1. If the histogram was biased towards the right it was indicating a 'bright' shot and i would adjust the EC to -1. What i was trying to achieve was an evenly spread histogram.
Sometimes it is not possible to get one that is evenly spread, sometimes mine look like a ski slope, fading away to the right. But as long as there is some information across the histogram i think that is ok.

With the 300D i think the EC is only accessible in the auto modes (i may be wrong). In the creative modes you use exactly the same display but by adjusting the shutter/aperture you achieve the same results and the marker moves to -/+ values.

i hope this makes sense.

[FlipsidE]

take black paper, a gray card and white paper in that order and make an exposure card. when you take a photo of it and have proper exposure, you will see a spike in middle of the left, middle of the center and middle of the right.

-nick
- This is an awesome way to check exposure. I should probably just go ahead and invest money into one of these (though they aren't exactly cheap). They make them in like 24" x 24" fabric form. And, they work SO WELL!

FlipsidE

[PacAce]

PacAce,

I use a DRebel...there isn't a dial on the back of the cam for EC. I know it has EC ability, but I don't think it's done via a dial on the back. I'll have to look into it.

And to everyone else, thanks for all the advice so far!! :)

FlipsidE
If you haven't found it yet, it's in page 75 of your manual.

[FlipsidE]

If you haven't found it yet, it's in page 75 of your manual.

Thanks!! I'm at work at the moment, so I haven't had time to scan the manual. I appreciate the info :)

FlipsidE

[FlipsidE]

Hmmm...so the DRebel can't use EC in M? Well, that seems rather limiting. Or is it like this with all the EOS DSLR's?

FlipsidE

[Jonny]

Hmmm...so the DRebel can't use EC in M? Well, that seems rather limiting. Or is it like this with all the EOS DSLR's?

FlipsidE

The 20D is the same. In M one dial controls Aperture and the othe controls Shutter speed. I don't really see any need for EC in M when you would just over/under expose by your own settings.

[PacAce]

Hmmm...so the DRebel can't use EC in M? Well, that seems rather limiting. Or is it like this with all the EOS DSLR's?

FlipsidE

Actually none of the EOS camera do. And that's for a very good reason, if you think about it. In M mode, you are adjusting shutter and aperture. You would ordinarily center the "needle" in the meter. If you want to apply an equivalent of EC, all you have to do is adjust the shutter and/or the aperture in the appropriate direction so the the "needle" move to the "EC" spot you want. :)

The reason for EC in the auto modes is because all the camera wants to do is always center the needle in the meter. You can try adjusting the shutter or the aperture and the camera will respond by adjusting the other control so that the needle is back in the middle again. So, you have to use EC to tell the camera to move the needle plus or minus a notch or two.

[FlipsidE]

PacAce,

After I wrote that post, it hit me that using EC in M probably wasn't practical. Thanks for the explaination!

FlipsidE