Help please with understanding the "Understanding Exposure" book.

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nigpd

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I have been avidly reading Understanding Exposure since getting it for Christmas. I'm finding it a great read especially as I'm new to DSLR photography and have only had my 450D a couple of months.

However, there is one aspect that I'm having trouble getting my head round and I'm hoping that someone will be able to help.

The author writes about different types of exposures, "telling a story exposures" using small apertures, "isolating exposures" using large apertures and "dont care exposures" using mid range apertures.

The author decides on what type of shot he wants to take for the correct creative exposure, and chooses the appropriate aperture setting. He then takes a meter reading from the approprite part of the view and adjusts the shutter speed to give the correct exposure, recomposes and then takes the shot.

I am trying to work out how to put the above routine into practice using my 450D and get some sort of repeatable way of working when taking these types of pictures.

Do I set the camera on aperture priority, then set the appropriate aperture, then use partial metering on the appropriate part of the view, set exposure lock, recompose, focus, then take the shot?

I have a mental block on this aspect of the book and putting it in to practice, so would appreciate any help.

Thanks in advance for your help

Nigel
 
I haven't read the book yet (it's on the way) but it sounds like the author is using the camera on manual mode in this example, since he is adjusting both the aperture and the shutter speed.

I think he means he focuses on the subject and takes a light meter reading, adjusting the shutter speed until the exposure is balanced on the 0 mark on the light meter and recomposes. This way (as with using AV mode), you can control the depth of field and tell the story (small aperture / small DoF) or isolate your subject (shallow DoF). Doesn't sound like he was using the Partial Metering mode unless the book says the background was very bright, in which he prob would.

If you are new to the camera and the way exposure works I recommend putting the camera in manual mode and experimenting with some of the things he does in that book. Then switch to AV mode and use the same settings, you will soon see that it actually doesn't matter what manual mode you use; you can achieve exactly the same thing in each, when you become accustomed to using the camera in manual mode you can start using other modes for speed since you will know what kind of shot you want and how to get it.

I am sure other more experienced people on this site can advise further.

P
 
Once you understand what the different settings do you will know what sort of aperture f number, shutter speed, iso and even metering mode will work best for the shot you want.

The quickest way to learn what does what is to use manual mode. Once you know what everything does you may (like me) choose to let aperture priority take care of the shutter speed for your chosen aperture for most shots. So I'd suggest learning how to do it in manual then either stick with manual or use your preferred mode once you really understand things.
 
The author is perhaps making this a bit confusing because all he's really doing is controlling depth of field, with the lens aperture. This is a separate operation from setting the exposure, which is controlled not only by the lens aperture, but also by the shutter speed and ISO setting. Two quite different photographic procedures. It's just that the two operations are usually combined, because they both involve adjusting the lens aperture.

To work this way, you must first secure the lens aperture (either a story telling one, or an isolating one, or an it doesn't matter one) in Av or Manual mode. How you then go about balancing the other exposure settings (using spot, partial, evaluative etc metering) is irrelevant in this case.

Does that make sense?

Richard.
 
I'd have thought the first bit of understanding exposure was to understand the three elements that create your photographic image... aperture size, shutter speed and film/sensor sensitivity.... and how in terms of increments we measure those by they relate to each other and then the particular nuances seen in varying each.
 
im going through the book myself just got it!and reading the chapter over and over to make things clearer. also i have refered back to the manual of the camera 450d a lot of times and am now making more sense of it all. but still im only used to it and every thing takes time
 
Thanks for all the help and useful comments guys.

I'm currently re-reading this part of the book again and will practice using the various exercises in the chapters about the 3 types of exposure.

hopefully it will become clearer
 
nigpd said:
I have been avidly reading Understanding Exposure since getting it for Christmas. I'm finding it a great read especially as I'm new to DSLR photography and have only had my 450D a couple of months.

However, there is one aspect that I'm having trouble getting my head round and I'm hoping that someone will be able to help.

The author writes about different types of exposures, "telling a story exposures" using small apertures, "isolating exposures" using large apertures and "dont care exposures" using mid range apertures.

The author decides on what type of shot he wants to take for the correct creative exposure, and chooses the appropriate aperture setting. He then takes a meter reading from the approprite part of the view and adjusts the shutter speed to give the correct exposure, recomposes and then takes the shot.

I am trying to work out how to put the above routine into practice using my 450D and get some sort of repeatable way of working when taking these types of pictures.

Do I set the camera on aperture priority, then set the appropriate aperture, then use partial metering on the appropriate part of the view, set exposure lock, recompose, focus, then take the shot?

I have a mental block on this aspect of the book and putting it in to practice, so would appreciate any help.

Thanks in advance for your help

Nigel
Click to expand...

And by time time he has done all that. The blue tit, he was going to take a picture of, has been and gone.:D:D:D
 
As daftbugger says "i cant help but think you may be over complicating things when you mention 3 types of exposures ... there is only 1 type of exposure , the correct 1"

Being a bit cynical, I think a lot of books are actually less than helpful when they over-complicate what are really quite simple concepts. Of course they have to do this, or the book would only be two pages long :suspect: Once you get past the confusing jargon (f/numbers, stops, fast/slow/wide/small/high/low apertures) and grasp the fact that the lens aperture, shutter speed and ISO enjoy a simple reciprocal relationship in setting exposure, what is actually being discussed falls easily into place.

How difficult can you make exposure? It's just using various camera controls to ensure that the sensor receives the correct amount of light, and the correct amount is always the same, regardless!

I've had a go at it here. It's a sticky burried on this site.

http://www.talkphotography.co.uk/forums/showthread.php?p=1122264#post1122264

Please let me know if you find it either helpful or unhelpful. I'd really appreciate the feedback :)

Thanks,

Richard.
 
daftbugga said:
http://www.uscoles.com/exposures.pdf
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I was going to make one of these from scratch today! You've just saved me an afternoon's worth of work!

With respect to the 'Understanding Exposure' book it does go through Shutter Speed, Aperture and ISO and then on to the '3 exposures'. These are the way the author works and quickly decides on the type of shot he is taking, not a be all and end all. I found it the most useful book I've ever read on Photography (I REALLY like books and have quite a few!). What it is missing is a detailed explanation of how to take a meter reading in different situations, I think this is where the OP is getting confused.
 
daftbugga said:
OI HoppyUK

you spelt my name wrong
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Sorry! That's makes two daftbuggas then ;) And thanks for your comments.

That uscoles link above is a good one! With the tables/dials it explains the thing which I believe baffles most people, and that is the halving/doubling relationship that exists between f/numbers, shutter speeds and ISO.

Once you understand that f/4 is actually twice as large as f/5.6, which is twice as large as f/8, and that therefore f/8 is also half the size of f/5.6, it's a heck of a lot easier work out that f/8 at 1/125sec provides exactly the same exposure as f/5.6 at 1/250sec. ISO just adds to the permutations available, as ISO100 needs twice as much light as ISO200, and so on. And while this makes exposure options far easier and more extensive, if all it does it add furthjer confusion to the situation, you're stumped.

Here's an idea for some helpful webby developer type person - take the uscoles tables and turn them into an active graphic on here, where you can set the correct exposure and instantly see all the variables, and with an ISO button to automatically ring the changes there. It would make a great sticky :)

Richard.
 
HoppyUK said:
Here's an idea for some helpful webby developer type person - take the uscoles tables and turn them into an active graphic on here, where you can set the correct exposure and instantly see all the variables, and with an ISO button to automatically ring the changes there. It would make a great sticky :)

Richard.
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That sounds like a challenge to me - i'll have a think now!
 
GrantT said:
What it is missing is a detailed explanation of how to take a meter reading in different situations, I think this is where the OP is getting confused.
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Exactly where my confusion stems from. In the chapters on aperture, the author talks about adjusting his shutter speed until a correct exposure was indicated in the viewfinder. How does my 450D do that I keep asking myelf?

Apologies as I may have not worded my thoughts correctly when I said three different types of exposure... I more properly should have said three different types of aperture setting, ie telling a story, singular theme and who cares.

I undersand that there is only one type of exposure, the correct one, and the author of Understanding Exposure talks about six correct exposures, being combinations of aperture and shutter speed, versus the one creatively correct exposure.

Its just the adjusting shutter speed till a correct exposure is indicated that I dont get
 
Try this. Compare exposure setting to filling a glass with water.

You need a certain amount of water to fill the glass. Same as you need a certain amount of light for the correct exposure.

The tap is your lens aperture, and you can either turn the water on hard (wide aperture, low f/number) or just a slow trickle (small aperture, high f/number).

And you can leave the tap on for a short time (high shutter speed) or for as long as you like (long shutter speed).

You can fill the glass either by turning the tap on hard for a short time, or slowly for a long time. The glass still gets filled the same.

Changing the ISO changes the size of the glass. A low ISO number is a big glass needing a lot of water, and a high ISO is a small glass, needing less.

At all times, the camera knows the size of the glass, it knows how much water comes out of the tap as you turn it, and it knows how long you can turn it on for.

The only variable the camera doesn't know is how bright the sun is shining - that's the water pressure in this analogy. Lots of light is high water pressure which will gush out of the tap fast, even if it's only turned on a little, but if it's darker then the water pressure is low and it will only trickle out even when the tap is full on.

In exposure metering, the camera measures the brighness of the light, the water pressure, and because it knows exactly what all the other factors are, it then presents you with a combination of camera settings - how hard to turn on the tap, and for how long - to fill the glass exactly, and give you correct exposure.

I just thought that up. Does it make things any clearer? Sure exposure settings can get confusing, but the concept is actually very simple. Like filling a glass.

The important thing to understand about camera settings is the halving and doubling relationship between all the exposure controls. 1/125sec is obviously twice as long as 1/250sec, and ISO 100 is half as sensitive to light as ISO 200. Less obvious is that f/4 passes twice as much light as f/5.6, which passes twice as much light as f/8.

That is what exposure setting is about. Exposure metering (measuring how bright the sun is, the water pressure in the analogy above) is a different thing. That is when spot, evaluative, and centre-weighted etc methods come in as all scenes are a bit different and some ways work better than others.

Phew! :D

Richard.
 
Hi Richard

thanks for your reply. its a superb analogy and one that makes the concept of exposure easier to understand.

at this early stage of my photography I guess its all about practice, making mistakes, understanding what's happening in camera and going out and trying again.
 
I purchased this book about 3 years ago when I was starting out and it was the best money I have ever spent on "kit" I still go back to it now but it helped me out no end !! I also spent alot of time getting to know my camera's settings better after I read it.
It does encourage to experiment with settings and I find Manual exposure so much easier now.

Dean
 
nigpd said:
Exactly where my confusion stems from. In the chapters on aperture, the author talks about adjusting his shutter speed until a correct exposure was indicated in the viewfinder. How does my 450D do that I keep asking myelf?
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In the viewfinder and on the lcd screen there is a scale from -2 to +2 with marks at each third ( e.g. -2 . . 1 . . 0 . . 1 . . 2 ).
When the camera is in semi auto modes (Av and Tv) this represents the exposure compensation that you have set (hold down the button marked AV and move the wheel behind the trigger).

In full manual mode (M) this scale changes to show you what the camera thinks is correct exposure - so stick it in manual, pick an aperture and shutter speed and press the shutter halfway down, if the indicator appears at 0 on the scale the camera believes you've got the exposure correct, if the indicator appears to the left it thinks the image will underexpose, to the right it thinks the image will overexpose.

If you are in Av (aperture priority) mode the camera will select a shutter speed that gets what the camera thinks is a correct exposure (i.e. aiming for zero on the scale if it were in manual). In Tv it will move the aperture to reflect the shutter speed you've set.

All very good, but the trick here is that what the camera thinks is correct isn't always right! In Av/Tv modes I almost always have -2/3rds exposure compensation set otherwise (especially in winter) I get blown out skies etc If I shoot in manual I normally aim for -2/3rds instead of 0 on the scale.

I'm sure that part of my struggles is that I should use the other metering modes more often, especially in high contrast situations. Its a whole new world when you start switching metering modes, I have to really stop and think before taking a shot when switching!

I'm currently reading the book too, the "triangle" logic that he talks about is built in to the camera, so I think half of it is a case of understanding how the camera decides what is correct metering, then see if you agree - if so, click! if not, make the necessary tweaks to get what you want. Comes down to what someone else said - you are smarter than the camera, all it can do is have a good guess.
I've found if I want to take a shot in low light the semi auto modes sometimes make the image too light, so I leave ISO alone, check what aperture/shutter the shot was taken at, switch to manual and stop the aperture down half or a full stop and go from there.

I'm as much of a rookie at this as anyone else, so any corrections to my waffling are welcome :)
 
HoppyUK said:
Try this. Compare exposure setting to filling a glass with water.

<rest snipped, but I'm quoting the whole post>

Richard.
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This is quite possibly the best analogy I have come across for explaining exposure. :clap: & :thumbs: to that man!
 
RichardtheSane said:
This is quite possibly the best analogy I have come across for explaining exposure. :clap: & :thumbs: to that man!
Click to expand...

Thank you RTS, and also nigph for your kind comments. Glad it works :) I've just thought of a bit more:

Make it a beer glass with a pint line. If the camera's automatically selected exposure setting accidentally fills the glass over the line, that is over-exposure, and if it fills under the line that underexposure. Adjusting the exposure compensation to plus (+) will add more water, adjusting it to minus (-) will take some away when you shoot the next picture.

Is your glass half full or half empty? Can't help with that one :D

Cheers,

Richard.
 
HoppyUK said:
Is your glass half full or half empty? Can't help with that one :D
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My glass is always half full when concerned with photography. I'm finding it a fascinating hobby both mentally and physically. Learning new stuff, doing something creative and also getting off my a**e is a perfect combination.

Each time I go out, I'm armed with new knowledge from the forum to try out. Why oh why didnt I start this sooner?

thanks again for the help Richard
 
In support of the OP, this was exactly the same query I was going to make regarding the book so you are not the only one who came away puzzled about that particular part of it nigpd!!

The advise is very useful to me as well - thanks everyone!
 
Brilliant thread that has explained and clarified the exposure issue wonderfully. Well done to HoppyUk and Crafts for simplifying the matter so succinctly :clap:
 
Suvv said:
Not sure of this helps?
http://dryreading.com/camera/index.html
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I've been looking all over for that! Well found! I think it's very good :) And I've bookmarked it for future reference.

What do other other people think? I would love to develop a series of graphics like that for a brilliant sticky on here, to also explain focal length, angle of view, depth of field, perspective, viewpoint etc. I reckon we could do it even better and would be happy to give it a go, if anyone fancies tackling the web-graphics side.

Let me know :)

Cheers Suvv,

Richard.
 
lucasthekopkat said:
In support of the OP, this was exactly the same query I was going to make regarding the book so you are not the only one who came away puzzled about that particular part of it nigpd!!

The advise is very useful to me as well - thanks everyone!
Click to expand...

I'll Third that too - and as previously said that water analogy is very good!
 
nigpd said:
Do I set the camera on aperture priority, then set the appropriate aperture, then use partial metering on the appropriate part of the view, set exposure lock, recompose, focus, then take the shot?
Click to expand...

How does one set exposure lock? On a Canon 400D in particular?

Thanks
 
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