Tutorial Everything you need to know about exposure theory but were afraid to ask 101.

Excellent summary - a good reminder of the basics and a good read on flash use for me as a relative newcomer

Thanks very much!
James
 
Just one comment:

Any given amount of light is called a “Exposure Value”, or EV
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Surely it's a Light Value or LV. EV is purely a function of shutter speed and aperture. It cannot be related to a light level until it is associated with an ISO number.


Steve.
 
Steve Smith said:
Just one comment:



Surely it's a Light Value or LV. EV is purely a function of shutter speed and aperture. It cannot be related to a light level until it is associated with an ISO number.


Steve.
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Steve... I know. This is a beginner's tutorial. I explain ISO later when they've got their head around reciprocity between shutter and aperture. They'll go away and google "EV" and that will be a first hit result with tables helping them to understand.... if they Google "LV" they'll be taken to insurance websites.

I appreciate your proof reading :).... bust sometimes, it's best to leave the absolute facts until later. It's for the same reason I've played a little fast and loose with the "facts" regarding depth of field too.


Remember the intended audience.
 
It's an excellent tutorial and the EV/LV thing doesn't detract from that. I raised the point though because it's not just a beginners' mistake to think EV is a measure of light level. Many more experienced photographers make the mistake too - possibly from a misunderstanding early on in their photographic learning. It doesn't help that some light meter manufacturers use EV in place of LV in their instruction manuals!

However, if you are going to follow it up with a piece on the relationship between EV, LV and ISO, then this can only be a good thing.


Steve.
 
Thanks for taking the time to do this @Pookeyhead. Much appreciated and will be kept for reference when I forget what im doing :rolleyes:
 
Steve Smith said:
I raised the point though because it's not just a beginners' mistake to think EV is a measure of light level.
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I do understand your concerns Steve.... but you have to strike a balance between being easy to read and accessible, and being pedantically correct from the outset. If a beginner can read that through in one sitting with their camera in their hands and come out of the other side understanding shutter speeds and apertures and see a marked improvement in their images, then producing someone who may at some point in the future confuses EV and LV is a small price to pay :)... because ultimately... that's more important, and knowing the difference between EV and LV doesn't actually matter that much, or have any influence over how good a photographer they are :) If they're interested, they'll learn the difference themselves, later, when it's just not something to get in the way of learning far more important things.


Steve Smith said:
However, if you are going to follow it up with a piece on the relationship between EV, LV and ISO, then this can only be a good thing.
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I've [with colleagues] just rewritten an entire degree course... doing any of more of this for pleasure seems like masochism right now LOL. Maybe another time. :)
 
I was very interested to read the section about flash, I've never used a flash before and have just started taking photos of my wife's 40s lindy hop dancing group who do demos in theatres and halls and museums etc. Previously I used the same techniques I use for my ice hockey photos (where flash is forbidden, so high ISO, wide aperture), but after talking it through with a few people on an airshow forum I am a member on, they all said flash is definitely the way to go if I want to improve, which I definitely do. This has given me a good place to start as I have zero experience with flash whatsoever.
 
Flash is useful, but if you're in a big venue, with high ceilings, and nothing to bounce flash off, then you may be better off with fast lenses and high ISO, as direct to subject on-camera flash looks awful in the vast majority of cases.

Grant W said:
I was very interested to read the section about flash, I've never used a flash before and have just started taking photos of my wife's 40s lindy hop dancing group who do demos in theatres and halls and museums etc. Previously I used the same techniques I use for my ice hockey photos (where flash is forbidden, so high ISO, wide aperture), but after talking it through with a few people on an airshow forum I am a member on, they all said flash is definitely the way to go if I want to improve, which I definitely do. This has given me a good place to start as I have zero experience with flash whatsoever.
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Pookeyhead said:
Flash is useful, but if you're in a big venue, with high ceilings, and nothing to bounce flash off, then you may be better off with fast lenses and high ISO, as direct to subject on-camera flash looks awful in the vast majority of cases.
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I might stick to what I know then and having just bought a 17-55 f/2.8 lens it should become a little easier rather than messing about with stuff I don't know about (at the moment).
 
Just dropping in my 2d! Brillent Dave! I have been trying to encourage my wife to get into Photography. No matter how i tried to explain those basics to her, she kept telling me "I dont get it" i showed her this the other night and after reading through it a couple of times she said "Ah now i understand" (Me gutted :)) but i think thats great feedback for you!
Apparently i didnt explain it very well :eek:.
The boss wants to know if you are going to write any more items.... To be fair, i think you have got the balance Bang on. Get the basics right first, clear and concise without all the heavy technical information with excellent use of analogies and illistrations. Good Stuff.

As Bryn says i'll read this when i loose the Plot!

Well Done i think you've done a excellent job. If she starts taking better photo's than me i'll blame you.
 
Really useful thank you! Every time I read over these essential 'fundamentals' (something I've done many times) I never fail to learn new things...
 
As a beginner, this thread has been really useful in understanding the basics of photography. Thanks!
 
kennysarmy said:
But why does a small hole (large aperture) have a greater depth of field ?
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Sorry.. don't check this thread much and you didn't quote or tag me, so I got no notification.

The effect is caused by the Circle of Confusion. All lenses can only focus on one point, and any point on front, or behind that point is defocused. To make things simpler, assume you were photographing a minute point of light.. a genuine point light source. At wider apertures (smaller f numbers) it will only appear as a point at the distance it is focused at. Move it (or the camera) even slightly in front or behind the point you are focused upon and that point light source will become soft, and start to take on the shape of the aperture it is passing through. For normal scenes this is just represented as softness. This is because light passes through the entire lens surface, including it's edge and spherical aberration (something present to some degree in all lenses) prevents all light rays from all the lens's surfaces being focused precisely in one point. Stopping down forces the light to pass through the centre of the lens more (the more you stop down the more this happens) and spherical aberration is thus reduced. As a result, the circle of confusion for out of focus objects becomes smaller, so we get the impression objects on front, or behind the lens are now sharper.

Cambridge In Colour have a good page with diagrams that help understand this here.

http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

I've no idea what level you're at, so if you're an absolute beginner, that link may be a bit overwhelming, but the diagrams really help illustrate what I was saying in a way typed words really can't do very well.
 
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Great thread. Really helpful to have all of these points in one place and with great explanations
 
Excellent thread! Like a few other people commenting here, I'm also starting out and found this thread very informative. Much appreciated!
 
You're welcome
 
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