EV confusion-please help

Discussion in 'Photography Beginners' Forum' started by Kathleen, Jul 22, 2008.

  1. Kathleen

    Kathleen TPF Noob!

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    Understanding those EV digits has really got my head in a spin! I've read several articles, but I'm not one for math & so it is all a foreign language to me-how many stops a digit represents?? Really, I guess what I need, or shall I say must know is where do I set the EV needle for - 2/3 ? I'm metering off of grass, therefore my need to know. Hope someone can help. with thanks
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    I don't think about EV values...I keep it to 'stops'...which can be either aperture values (F numbers), shutter speeds or ISO settings.

    You would adjust the needle away from -0- (exposure compensation) when you are metering off of things that you know are different from middle grey. For example, if you are metering off of a black dog, you know that the dog is darker than middle grey, so you need to dial down the exposure (negative EC). If it's a light subject, then you would dial up the exposure (positive EC).

    Grass is actually pretty close to the reflectivity of middle grey, so when using grass to set your exposure, you wouldn't adjust the exposure at all...which is why it's easy to use grass.
     
  3. dEARlEADER

    dEARlEADER TPF Noob!

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    I think she is getting this from Petersons book.... who suggests if you are photographing a dark subject to meter something green and back up 2/3 stop.....
     
  4. Kathleen

    Kathleen TPF Noob!

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    Yes, Petersons book. A real eye opener for me. I understand the direction of minus or plus stops, but feel rather dumb not being able to understand what each digit represents as far as how many stops. It's all so complicated, so really all I need is where do I set the needle for a -2/3 ?
     
  5. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    That wouldn't be correct. If you meter something green (grass, foliage etc) then those settings would be 'correct' for anything in that light...dark, light or whatever. It's like using a grey card.

    If you are shooting a dark subject and 'metering' off of a dark subject, then you would take away some exposure.

    It's all arbitrary anyway. If you want it darker, then subtract exposure. If you want it brighter then use more exposure.
    With digital, I just shoot...check the histogram...adjust and shoot again.
     
  6. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    What camera do you have?
    Most DSLR cameras have a scale that displays 'stops' in 1/2 or 1/3 increments. So the scale should look like this:
    -2 . . -1 . . 0 . . 1 . . 2
    Each 'click' will be on notch down the scale...three clicks is one full 'stop'.
     
  7. Kathleen

    Kathleen TPF Noob!

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    Canon Rebel. I tried using the grass & just going with what the camera showed as being the correct exposure. But following that rule and not adjusting the EV as Peterson suggests, checking my histogram the photo was under exposed. I don't know if Petersons' advice is correct or not, but it does seem to apply.
    Thanks for the scale, I see it a little clearer now. :)
     
  8. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    If it's a darker subject, it might have a histogram that is bias to the left with 'correct exposure'. This metering technique is an attempt to make the photo look like what the subject actually looks like.

    That being said, 'correct exposure' isn't always the best option for digital photography. With digital, the best result if often to have a histogram that is bias to the right (bright) but without clipping (loosing detail). This gives you the most 'information' in the image. Then you can easily adjust it with software, for great results. This technique is called 'Expose to the Right'.
     
  9. dEARlEADER

    dEARlEADER TPF Noob!

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    (insert troll)

    I've been saying for a while that Petersons Understanding Exposure is mostly out dated and old school. Even the reissue for digital. He has a good way of explaining Aperture etc.... but the other half of the book is based on old metering techniques that are irrelevant with todays metering..... he even admits in his book that matrix metering is superior and the only reason he doesn't use it is because he is an old soggy log....

    Peterson blows.... but you would think he is Hugh Hefner on this forum.....
     
  10. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    I haven't read the book...but I can tell by the questions that get asked, that you are right. A lot of the metering lessons involve metering off of other things. There is nothing wrong with that, that's pretty much what I learned to do. But it can be confusing when people don't understand the theory behind it.

    And now with digital, it's just really easy to use the histogram instead.
     
  11. reg

    reg TPF Noob!

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    That, and the fact that I will *never* forgive him for the deluge of "so i wanna set 2 my storytelling apature, and i think thats like 5.6 on my lens right?".

    He gives really sweeping general ideas that only make things worse for the beginners that read the book, instead of just telling people how to control DoF he does that dumb chit with the storytelling aperture and blah blah blah.
     
  12. JD in Socal

    JD in Socal TPF Noob!

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    Peterson's guideline of -2/3 is accurate if you are photographing dark, lush grass or dense foliage, either of which is supposed to be darker than middle gray. For generic, ordinary playground grass with bare spots it will result in an underexposed image. I think there is some very good info in the book and I recommend it to others. Like anything, it is most valuable when the info is understood and mixed with some experience and experimentation.


    JD
     

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