Histograms :-s

[lewtashjosh]

Hi I'm struggling to understand the histogram. I have looked at the tutorial pages on this site but I am still rather confused about them, could someone help maybe I'm over thinking it but just cant grasp it.

Thanks / Lewis

[carregwen]

You are probably making the mistake (that most make) of trying to see some kind of shape that equates to the structure (shape) of your shot. All the histogram shows is a graphical representation of the occurance and spread of something - in this case light tones on a tonal range between pure black (the left side) and pure white (the right side) and everything (if it's there) in between.

Here is a shot created in CS5 with it's histogram. The thin bar on the left is pure black in the shot. The bar on the right is the white in the shot, and the bar in the middle is the middish grey. The height of each bar represents the relative percentage amount that each tone forms in the image. The blacks bar (on the left) is higher because there are more black in the shot. There are only three tones in this shot, so there are only three bars. You have a total of 256 tones, because the tonality has to work in 8 bit mode and binary 11111111 is 256. I deliberately put black on either side to show you that it doesn't matter where the tone occurs, it just matters that it does occur.

If you have some very high bars on the far right and/or left then you probably have some blown/underexposed detail. So, take a shot and chimp it to see if you have any bars in the extremities. A little bit may be OK, depending on the subject, but you don't want too much. If it is too much then adjust the exposure, either via the camera settings, or put an ND grad filter on if it's specific brightness, and reshoot to get the tones within an acceptable range.




Don't make the mistake of thinking that all histograms have to be nice pyramid shapes. here is a very striking and effective shot of mine. The histogram looks rather odd though, because there isn't a great deal of mid tones. It still works though, as a shot. It all depends what you are shooting and what effect you want.

[Peter Ryan]

Great explanation and example Rob. Do you mind if I borrow it for my students - credits will be given?

[carregwen]

Great explanation and example Rob. Do you mind if I borrow it for my students - credits will be given?

No problem, but I just changed the image to make it simpler.

[Peter Ryan]

Thanks Rob.

[Wirefox]

Excellent explanation Rob and I love the stairs.

[carregwen]

Excellent explanation Rob and I love the stairs.

That's good. You can vote for it in the next mini-comp!

[Blazing fire]

Excellent post, carregwen! Perhaps McQ might consider adding a few of your sentences to the tutorial .

Eg

The height of each bar represents the relative percentage amount that each tone forms in the image.
If you have some very high bars on the far right and/or left then you probably have some blown/underexposed detail.
Don't make the mistake of thinking that all histograms have to be nice pyramid shapes... It all depends what you are shooting and what effect you want.

Once again, thank you for your invaluable contribution!

[rob marshall]

Good simple tutorial Photography video tutorials

[Wirefox]

Tense nervous headache Rob? Can I have two IDs too please Donald? One for the cute cuddly happy go lucky me and one for Ansel Adams threads.

What I really want to know is what Carregwen is getting up to when Rob is logged on to CiC. I think maybe Rob has had a visit from Toadslayer's aliens. Stranger things have happend in deepest Wales....Torchwood

[rob marshall]

Tense nervous headache Rob? Can I have two IDs too please Donald? One for the cute cuddly happy go lucky me and one for Ansel Adams threads.

I think you need a third for taking the water out of me. There are no rules to say you can only have one account.

What I really want to know is what Carregwen is getting up to when Rob is logged on to CiC.

Usual stuff, taking more drugs than 'Keith', womanizing with Welsh harlots, indulging in Bacchanalian orgies, and spending quality time in Photoshop. Why don't you try it.

[Katy Noelle]

Tense nervous headache Rob? Can I have two IDs too please Donald? One for the cute cuddly happy go lucky me and one for Ansel Adams threads.

Extreme side-splitting LOL! Snort! Tears!

I'd like two, too, please - I like to talk to myself!

What I really want to know is what Carregwen is getting up to when Rob is logged on to CiC. I think maybe Rob has had a visit from Toadslayer's aliens. Stranger things have happend in deepest Wales....Torchwood

I've been wondering about that, too.... I'm glad that you said it first!

However, if it's the new avatar that you're talking about - headache-wise, that is, I think that it's the new meds in his cabinet (I suspect steroids but, whatever it is - he's subtly becoming more brilliant.... )

For some reason, I've been singing this song to myself lately (since Toadslayer showed up, actually....)

http://www.youtube.com/watch?v=JUMXJ...eature=related

[Donald]

For some reason, I've been singing this song to myself lately

In which case, you need to speak to Rob about getting some of Carregwen's medication!

[rob marshall]

In which case, you need to speak to Rob about getting some of Carregwen's medication!

Who is Carregwen?

[Wirefox]

Usual stuff, taking more drugs than 'Keith', womanizing with Welsh harlots, indulging in Bacchanalian orgies, and spending quality time in Photoshop. Why don't you try it.

I will just grab my anorak and slippers and I will be with you in five (5 days that is...thats how long it takes to get to Cardiff by National Coach)

Actually I have been spending what little time I have on PS (GIMP). Something you said about visiting old images with new skills. Only problem was I discovered I didn't have any new skills. Transpires that I had dreamt it all. It seems I am back to square one wondering what lens to use for a cat licking its **** backdropped with with a pile of washing and a box of Omo. Thats it, can't get any further. I am seriously thinking about a facebook account and a Flickr Group entitled "Please lie profusely about how good my photos are"...wait a minute don't they do that as default? It is either that or jumping of the end New Brighton pier with a 1D around my neck.

[rob marshall]

It seems I am back to square one

You probably never left it...

wondering what lens to use for a cat licking its **** backdropped with with a pile of washing and a box of Omo. Thats it, can't get any further.

You could always try posterizing the shot in GIMP and call it 'Posterized cat licking it's ****'

[Katy Noelle]

Ah.... who needs a cabinet? You guys are the best meds! ("Bats eyelashes and smiles sweetly" smilie!)

[rob marshall]

How did we manage to get from post #1 with Morse's side-kick in Oxford asking a simple question about histograms, to this...?

(Note: Morse is a famous detective character from a TV series of that name in the 1986-2000 period. And I should know as I have just watched all 33 episodes on Love films.)

[Wirefox]

You probably never left it...

You are supposed to encourage me and lie about my talents. I am suffering from photographers block here not delusional ego mania.

You could always try posterizing the shot in GIMP and call it 'Posterized cat licking it's ****'

Genius!!! You have it Watson. I can see the comments on Flickr as we speak.....

"outstanding photography"
"I was physically moved by this vision of creative loveliness"
"can I buy this as a 6fx6ft print?"
"my names Jed and I own a Nikon D3 and a 44 Magnum. I sure sure would like to marry your cat"
"I would love you to join my Upskirt Cat Group..here's a link to a tub of blue smarties and some ladies in the Warrington area who would love to meet you"

[Katy Noelle]

In which case, you need to speak to Rob about getting some of Carregwen's medication!

That will definitely make it worse!