FYI: To noobies: the Histogram doesn't tell you if you are properly exposed or not.
Oct 16, 2013 13:12:20 #
Frequently in the 'hog forums you'll read someone giving someone else advice on how to get a proper exposure and they'll say "check your histogram, the information isn't supposed to be all the way to the left..." or something similar.
But I have to say...this just isn't true at all. Sorry.
The histogram just tells you the distribution of tones within your image...it has no idea what your artistic intent is...it cannot determine exposure...or even help you determine your desired exposure.
Example:
You'll see below 4 images. I set the camera on ISO 400 ss 1/125 and f/2 (the correct exposure for my office)
In them I changed the framing of the coffee bag to include light and dark items but never changed the exposure.
Noticed that the histo and camera meter wanted to change it every time as if the exposure was changing when it really wasn't.
In the first shot I took it where my black backpack was accounting for a "medium" percentage of the overall shot...the light to dark tones are about even...and the histo is "fairly" evenly distributed.
In the second, I pulled back so that the backpack accounts for much more of the tonal range...noticed that now the histo is decidedly skewed to the left.
Should I change the camera's exposure so that the tones are more towards the middle?
Of course not...the exposure (amount of light falling on my coffee bag) didn't change...why should the camera settings change...? because the histo changed?
In the third image the blue wall and the coffee bag are about as "medium toned" as I could get here in my office...but the camera settings didn't change....but the histo did...what does that mean?
Nothing.
In the last image I put the bag of coffee on a shelf in front of my white board....so the histo now shows much of the curve above middle grey....so do I lower the ISO to compensate?
Here is the biggest question: If I hadn't already known that my office is 1/125 f/2 ISO 400 and kept the settings set in one spot...would I have changed the ISO up to ISO 800 as the camera wanted just because the histo said so?
How about down to ISO 200 because the histo saw the white board and wanted to go a stop down?
This is why the histo is useless in determining exposure...(really just one reason) it also can't guess what your artistic intent is either...high key...silhouette...etc...
Just thought I'd explain.
But I have to say...this just isn't true at all. Sorry.
The histogram just tells you the distribution of tones within your image...it has no idea what your artistic intent is...it cannot determine exposure...or even help you determine your desired exposure.
Example:
You'll see below 4 images. I set the camera on ISO 400 ss 1/125 and f/2 (the correct exposure for my office)
In them I changed the framing of the coffee bag to include light and dark items but never changed the exposure.
Noticed that the histo and camera meter wanted to change it every time as if the exposure was changing when it really wasn't.
In the first shot I took it where my black backpack was accounting for a "medium" percentage of the overall shot...the light to dark tones are about even...and the histo is "fairly" evenly distributed.
In the second, I pulled back so that the backpack accounts for much more of the tonal range...noticed that now the histo is decidedly skewed to the left.
Should I change the camera's exposure so that the tones are more towards the middle?
Of course not...the exposure (amount of light falling on my coffee bag) didn't change...why should the camera settings change...? because the histo changed?
In the third image the blue wall and the coffee bag are about as "medium toned" as I could get here in my office...but the camera settings didn't change....but the histo did...what does that mean?
Nothing.
In the last image I put the bag of coffee on a shelf in front of my white board....so the histo now shows much of the curve above middle grey....so do I lower the ISO to compensate?
Here is the biggest question: If I hadn't already known that my office is 1/125 f/2 ISO 400 and kept the settings set in one spot...would I have changed the ISO up to ISO 800 as the camera wanted just because the histo said so?
How about down to ISO 200 because the histo saw the white board and wanted to go a stop down?
This is why the histo is useless in determining exposure...(really just one reason) it also can't guess what your artistic intent is either...high key...silhouette...etc...
Just thought I'd explain.
Oct 16, 2013 13:22:05 #
This is why it is important to "spot" meter critical scenes... The meter is just giving you a guideline , which in & of itself, may or may not be correct. It isn't infallible as it is a "reflective" reading, not an "incident" reading...
Oct 16, 2013 13:24:42 #
Screamin Scott wrote:
This is why it is important to "spot" meter critical scenes... The meter is just giving you a guideline , which in & of itself, may or may not be correct. It isn't infallible as it is a "reflective" reading, not an "incident" reading...
Well...that's what I'm saying...it's NOT a guideline...the information it provides doesn't tell you if you're exposed correctly or not...the ONLY use it is, is to tell you if the scene exceeds your camera's dynamic range capability, and even THEN I'd argue...who cares? What if you blow out a portion of the image that you don't care about?
How about letting some of it fall into black?
It just doesn't really help.
Oct 16, 2013 13:30:57 #
You have to decide what's more important in the scene, the darker or the lighter side of the histogram & not let those ranges go to either extreme side so as to be able to retrieve the detail ...If you are doing a high key portrait, you will want the data to be more to the right side of the histogram, but not all the way over. It's all about understanding your camera, it's meter, & how the histograms values affect post processing
rpavich wrote:
Well...that's what I'm saying...it's NOT a guideline...the information it provides doesn't tell you if you're exposed correctly or not...the ONLY use it is, is to tell you if the scene exceeds your camera's dynamic range capability, and even THEN I'd argue...who cares? What if you blow out a portion of the image that you don't care about?
How about letting some of it fall into black?
It just doesn't really help.
How about letting some of it fall into black?
It just doesn't really help.
Oct 16, 2013 13:32:30 #
I think that the histo that you are showing shows the distribution of the Red, Green and Blue channels. There is another histo that shows dark pixels to light pixels and that would be a better guide as to obtaining proper exposure. AND just what is proper exposure? Who makes that call?
Oct 16, 2013 13:33:02 #
Screamin Scott wrote:
You have to decide what's more important in the scene, the darker or the lighter side of the histogram & not let those ranges go to either extreme side so as to be able to retrieve the detail ...If you are doing a high key portrait, you will want the data to be more to the right side of the histogram, but not all the way over. It's all about understanding your camera, it's meter, & how the histograms values affect post processing
Or let them blow out completely...which goes right back to...the histo is useless for determining exposure.
Oct 16, 2013 13:34:46 #
But not artistic intent...
rpavich wrote:
Or let them blow out completely...which goes right back to...the histo is useless for determining exposure.
Oct 16, 2013 13:35:49 #
I just did an experiment....I'm pretending I'm a noob and I'm letting the camera drive ISO and the exposure.
I took the image of my backpack and coffee...properly exposed at ISO 400 f/2 1/125.
Then I took the same image and this time put the camera on auto iso...it produced a lovely histogram...but check out the washed out blacks and the washed out blue paint on the wall.
The camera chose ISO 1000!
If I hadn't already known what the exposure was and had a reference point, I might not even realized how messed up my photo is...and based on a centered histo...why would I think anything is amiss?
It's useless for determining exposure. (Not that it has no use at all...let's not argue about that but stay on my original point)
In fact..check out the great "centered up" histo! and nothing exceeding the high/low thresholds...if that's the method that I used in deciding if I'd taken a good exposure or not...I'd have produced a crappy washed out image.
I took the image of my backpack and coffee...properly exposed at ISO 400 f/2 1/125.
Then I took the same image and this time put the camera on auto iso...it produced a lovely histogram...but check out the washed out blacks and the washed out blue paint on the wall.
The camera chose ISO 1000!
If I hadn't already known what the exposure was and had a reference point, I might not even realized how messed up my photo is...and based on a centered histo...why would I think anything is amiss?
It's useless for determining exposure. (Not that it has no use at all...let's not argue about that but stay on my original point)
In fact..check out the great "centered up" histo! and nothing exceeding the high/low thresholds...if that's the method that I used in deciding if I'd taken a good exposure or not...I'd have produced a crappy washed out image.
Oct 16, 2013 13:40:48 #
a3dtot
Loc: Houston, TX
Thanks for the clarification. I'm not really a noobie to photography (ie film) but I'm just now really trying to understand my digital camera. I find I struggle with white balance bracketing, some of the metering and with the histogram discussion I was getting a little confused. After reading about histograms I went to my manual and began to study the histogram and I was still confused. Thanks for clarifying this a little for me. If I understand correctly the histogram is showing me the intensities of light in the photo
and as you stated this is not the exposure but simply what is in the photo. I think the histogram may be useful in understanding how it perceives light in a given photo which can be used as additional info about that photo.
and as you stated this is not the exposure but simply what is in the photo. I think the histogram may be useful in understanding how it perceives light in a given photo which can be used as additional info about that photo.
Oct 16, 2013 13:43:12 #
rpavich wrote:
Frequently in the 'hog forums you'll read someone ... (show quote)
You are correct. There are times when the histogram is wrong.
However there is a high degree of correlation between proper exposure and it.
Oct 16, 2013 13:43:12 #
Screamin Scott wrote:
But not artistic intent...
Which is exactly what I stated in the OP...let's not confuse this by getting to side-barred...ok?
I want to keep this conversation on point if we can :)
Oct 16, 2013 13:44:11 #
joer wrote:
You are correct. There are times when the histogram is wrong.
However there is a high degree of correlation between proper exposure and it.
However there is a high degree of correlation between proper exposure and it.
Wrong.
It's not "wrong" or "right"...it can't be...it just "is"...
There is no such thing as a "good" histo or a "bad" histo...a good image could have 90% of the tones jammed all the way to the left and even past!
There is NO correlation between proper exposure and the histogram.
It ONLY reports what you've already done...period.
Oct 16, 2013 13:46:13 #
a3dtot wrote:
Thanks for the clarification. I'm not really a noo... (show quote)
You're on the right track...but not "intensity" only "shades of grey..." that's all.
Oct 16, 2013 14:13:59 #
Many of my images will have the bulk of the histogram crammed up to the left (underexposed side as I shoot a lot of macro with a ring light & a relatively fast (1/200th) shutter speed. This blackens any distracting backgrounds. Thus my subject gets properly exposed, but since there is so much black background, the histogram skews to the left... All about understanding your camera & the way metering works with it......
Oct 17, 2013 08:42:55 #
rpavich wrote:
Frequently in the 'hog forums you'll read someone ... (show quote)
You had better understand a histogram first before you start telling everyone a histogram is useless. You just made the world know how stupid you are. You have a lot to learning to do. You also neglect to say what camera you are using and what lens and focal length. Also shooting at f2, using a 35mm lens,, your DOF at 10' is less than 2 feet. If a longer focal length was used, the DOF would be less. Rather shallow DOF
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