metering /focusing help

[Aunt Flo]

Hi guys (nervous)
Ok here's a newbie question - no laughing at the back though!

I've been browsing a couple of photography books at the library (I should really rent them out). I like what I read about ISO, shutter speeds & aperture, but I'm missing something really basic, maybe I should have just stuck to one book?
Anyway my problem is with focusing & metering. - one book uses the term focus when discribing a picture taking scene, but the other book calls it metering.

scenario 1.
Person in the garden. Using Spot focus, half press shutter button on the person and then recompose. take shot.

scenario 2.
Ocean Sunset. meter for the brightest part of the sky near the sun by half pressing the shutter button, recompose. take shot.

So do I have to half press the shutter button the meter the scene or not? Or is half pressing the button just focusing on the subject only? I notice the shutter speed/aperture info in the lcd screen changes constantly anyway, just by moving it a little bit.

My Nikon D5100 arrived yesterday just need to get my head around a few silly things.

Thank you!

 

[Tringa]

Hello and welcome to the forum.

Half pressing the shutter release activates the auto focus on your camera (some cameras allow other buttons to be used for focussing but in general this applies to, as far as I know, all DSLRs).

The meter works all the time you have the camera switched on. As you have seen the speed and aperture can change constantly.

However, the exposure may be locked to the focus point, so the meter reading is taken from what you are focussed on, which is what I think is being alluded to in your second scenario.

Hope this has helped and has not caused more confusion.

Dave

 

[HoppyUK]

Welcome Flo

What half-pressing the shutter release basically does is wake up the camera, assuming it's switched on. And usually by default it will activate the AF, start the metering, activate the image stabilisation (Nikon's VR) and wake up the flash if that's dozed off too. Though all these things can usually be switched individually too.

Focusing a metering are two completely different operations, though they're usually done simultaneously. Tip: if you want to understand exposure, learn to read the histogram (not hard) and have blinkies enabled. That's the highlight over-exposure warning that flashes black/white on the LCD.

 

[fatmarley]

In simple terms, exposure is how bright or dark your picture will be. Imagine you lock the exposure on something bright like the sun, you then move the camera to take a picture of the whole scene. The camera will think "OMG that's bright!" and let less light in, and as a result you get a darker overall picture.

 

[Suvv]

As others have said half-pressing the shutter button will lock the focus allowing you to focus on something specific, recompose and take the shot.
With many cameras you can also set the half press of the shutter button to lock the exposure as well, allowing you to expose for the sky (or land), recompose and take the shot.
With the D5100 I believe that it is in the Custom Menu, option c1.
The D5100 also has an AE-L/AF-L button Custom Menu option f5. You can set this button to lock the focus and exposure or lock just one of them while it is pressed. You can also set it to lock and hold the exposure so that you do not have to keep it pressed.
FWIW I use my shutter button half pressed to lock focus and have the AE-L/AE-F button set to lock and hold exposure. This allows me to focus on one thing, expose on another and take a re-composed shot with those settings.

 

[Aunt Flo]

Thank you everyone, It's a bit clearer now. Need to get out there and practice. Will post a few shots to see what people think. I've been reading through a few older posts too and have come to the conclusion that the book by Brian Peterson (Understanding Exposure) might be worth reading and so have ordered that.

Thanks for helping
Flo

 

[HoppyUK]

Thank you everyone, It's a bit clearer now. Need to get out there and practice. Will post a few shots to see what people think. I've been reading through a few older posts too and have come to the conclusion that the book by Brian Peterson (Understanding Exposure) might be worth reading and so have ordered that.

Thanks for helping
Flo

That depends who you ask He will tell you precisely zero about the histogram and blinkies, which are the two greatest gifts handed down by the Gods of Digital.

 

[tijuana taxi]

As ever where Mr Peterson is concerned I echo Richard's comments, histogram is the best guide you have for getting the exposure right (apart from your own eyes)