Sorry if this seems a beginners type question, but a beginner I am and could do with some more help
The learning curve is getting steeper for me at the moment. When I started out, I thought I was getting quite good shot. Then the realisation that in fact a lot of it was luck with exposure and BG's etc has struck and I am now looking at the more technically skilled side of digital photography. ramble ramble
My question is on exposure.
Could you recommend any particular books/sites that explain exposure settings simply yet tackle the technical side of it too?
The sort of questions I would like answered are things like the difference between shooting at ISO 200, f8 at 1/500th and shooting at ISO 400, f11 at 1/500th. Is this a stupid question?
EDIT: Sorry if it seems a vague question, but I felt prompted to ask this after a critique on the UK site stated -
" I've also just been looking at the technical details you've posted. You are fortunate to have made a sharp image with a ss = 1/160s. For a swimming duck you usually need a ss = 1/320s or faster. It is also a mistake with digital to think that a lower ISO-equivalent equates to better image quality. The native sensitivity of the Canon image chips is thought to be 200 ISO-equivalent. I think you should consider shooting at a higher ss and higher ISO"
I am aware that noise starts to creep in at higher ISO's and the DOF factor with aperture and the need for higher SS to freeze action etc, but reading this seems to imply something more technical?
Hope this makes sense.
Regards
Posted by Kent Staubus on March 18, 2006 at 4:50 PM
Not a stupid question at all. In your above example, with f11 you have more in focus (in front of and behind the bird) than you would with f8. With birds, you normally want to blur the background so the bird stands out better. You also can get faster shutter speeds shooting a wider aperatures, which is good for birds. Also, your camare might make slightly higher quality images with ISO 200 than ISO 400.
It's important to separate the terms here - exposure is the amount of light that reaches your sensor. In that sense 1/500 at f/8 is twice the exposure value of 1/500 at f/11.
ISO rating is a measure of sensitivity. When your sensor is set to ISO 400 it is twice as sensitive (and therefore needs half the exposure) as ISO 200.
DOF is a result of magnification and aperture. Assuming the same magnification (same lens focused at the same distance), an aperture of f/11 will deliver greater DOF than f/8. The reason is that out-of-focus areas will be rendered in smaller dots (called circle-of-confusion, or CoC for short).
The image quality difference at different ISOs depends on the capture medium. High ISO film requires larger grains of silver halide, therefore it appears more grainy (duh). Digital sensors have a different problem - the sensor has an ideal/native sensitivity in which it can ccurately measure the amount of light falling on each photosite. If you force it to a higher ISO you are essentially making it "see" less light than it would ideally require and forcing it to guess the proper color/detail based on it. The result is lower image quality (which appears in the form of image noise).
When determining the best setting for a given situation you need to balance your need for shutter speed, DOF, and image quality. Often you can't have the ideal combination of all of them and you need to decide whether mode DOF is worth using a slower shutter or if a faster shutter is worth some added noise etc.
The aperture numbers, f2.8, f4, f5.6, f8...etc. (known as f-stops) are multiples of the square root of two. If you notice, every other one is a multiple of two. They represent a ratio between the area of the aperture and the focal length of the lens. The apertures represented by these f-numbers therefore are equivalent in lenses of different focal lengths. Changing the focal length alone will not change the exposure. The lower the f-number, the larger the aperture. Lowering the f-number by one stop increases the area of the aperture by a factor of two, doubling the amount of light passing through it. (I think perhaps they are called stops because the aperture ring on the lens stopped with a click at each full f-number. Canon EOS lenses don't have an aperture ring.)
To keep the same exposure, you must change the shutter speed accordingly. If you double the area of the aperture (enlarge the aperture by one stop) then you must cut in half the length of time the film or sensor is exposed, that is, you must change the shutter speed from say 1/125th to 1/250th of a second.
You use the aperture and shutterspeed to control elements of the photo - aperture for more or less depth of field, shutterspeed for freezing or blurring motion or to reduce the softness of an image due to camera shake. Sometimes you must compromise, sacrifice depth to stop action, for example.
The ISO rating represents different sensitivities of film or digital sensor. With film you must change the roll of film to change the ISO. With the advent of digital photography you can vary the ISO with each shot. This will allow you to mitigate your compromises between aperutre and shutterspeed. Each ISO number - 100, 200, 400, 800 - is double or half the one next to it. ISO 200 is one stop faster than ISO 100; ISO 400 is one stop faster than ISO 200. (The term faster means it will let you use a faster shutterspeed for any given aperture.) Higher ISOs generally have more noise or grain, though the noise or grain at ISO 400 may be an acceptable compomise if it allows you to use the aperture and shutterspeed that you need to make the photo.
In your swimming duck example, you could have increased your shutter speed by one stop from 1/160th to 1/320th of a second, without changing your aperture, by increasing your ISO rating by one stop. If you were shooting at ISO 100, then ISO 200 probably would have been satisfactory. If you were shooting at ISO 400, then ISO 800 may have had too much noise - that can be subjective. From the comment you received it would seem that the swimming duck was sharp enough at 1/160th, so in that particular case a higher ISO and hence a faster shutterspeed wasn't necessary.
I try to keep my ISO as low as conditions will allow. When I was shooting film I used film rated at ISO 100 and occasionally would push it to 200. I didn't like the look of the grain of higher ISO films. Now with digital, I still usually shoot at ISO 100, or ISO 200 if need be, and seldom at ISO 400.
To answer your question, the difference between shooting at ISO 200, f8 at 1/500th and shooting at ISO 400, f11 at 1/500th would be increased depth of field and increased noise, either of which might or might not be noticeable. But basically, in terms of exposure alone, they would be the same.
Hope this helps
Posted by Jack Graham on March 18, 2006 at 11:11 PM
Graeme,
All of the above is helpful & correct.
However, your question concerned books about explaining exposure. is ( in my opinion ) to get a hold of John Shaw's book: Nature Photography Field Guide . John explains exposure better than anyone I have ever heard ( or read).
Guy's & Kent;s replies were right on too. They "get it".
I recenly purchased my 1st Digital SLR ( Nikon D200). I feel like I can speak for Guy & Kent in saying, " I am glad I learned on film".because sooooooooooo many principles of digital photography is based on the "old fashioned" film principles.
One you master the exposure thing, and you will , you can feel good about making pleasing images. Ir's not really that complicated, just some books and explanations make it that
way. Guy & Kent couldn't have made it better---( a book guy's?).
I still drive around looking for "medium tone". I was in a restaurant last week and the waiter asked me if I was ready to order. I answered " In a few minutes". he asked if I had questions. I replied" Yes--- it the table cloth medium or - 2/3rds.........? It didn't go over too well.
Discussion
6 repliesSorry if this seems a beginners type question, but a beginner I am and could do with some more help
The learning curve is getting steeper for me at the moment. When I started out, I thought I was getting quite good shot. Then the realisation that in fact a lot of it was luck with exposure and BG's etc has struck and I am now looking at the more technically skilled side of digital photography. ramble ramble
My question is on exposure.
Could you recommend any particular books/sites that explain exposure settings simply yet tackle the technical side of it too?
The sort of questions I would like answered are things like the difference between shooting at ISO 200, f8 at 1/500th and shooting at ISO 400, f11 at 1/500th. Is this a stupid question?
EDIT: Sorry if it seems a vague question, but I felt prompted to ask this after a critique on the UK site stated -
" I've also just been looking at the technical details you've posted. You are fortunate to have made a sharp image with a ss = 1/160s. For a swimming duck you usually need a ss = 1/320s or faster. It is also a mistake with digital to think that a lower ISO-equivalent equates to better image quality. The native sensitivity of the Canon image chips is thought to be 200 ISO-equivalent. I think you should consider shooting at a higher ss and higher ISO"
I am aware that noise starts to creep in at higher ISO's and the DOF factor with aperture and the need for higher SS to freeze action etc, but reading this seems to imply something more technical?
Hope this makes sense.
Regards
Kent in SD
It's important to separate the terms here - exposure is the amount of light that reaches your sensor. In that sense 1/500 at f/8 is twice the exposure value of 1/500 at f/11.
ISO rating is a measure of sensitivity. When your sensor is set to ISO 400 it is twice as sensitive (and therefore needs half the exposure) as ISO 200.
DOF is a result of magnification and aperture. Assuming the same magnification (same lens focused at the same distance), an aperture of f/11 will deliver greater DOF than f/8. The reason is that out-of-focus areas will be rendered in smaller dots (called circle-of-confusion, or CoC for short).
The image quality difference at different ISOs depends on the capture medium. High ISO film requires larger grains of silver halide, therefore it appears more grainy (duh). Digital sensors have a different problem - the sensor has an ideal/native sensitivity in which it can ccurately measure the amount of light falling on each photosite. If you force it to a higher ISO you are essentially making it "see" less light than it would ideally require and forcing it to guess the proper color/detail based on it. The result is lower image quality (which appears in the form of image noise).
When determining the best setting for a given situation you need to balance your need for shutter speed, DOF, and image quality. Often you can't have the ideal combination of all of them and you need to decide whether mode DOF is worth using a slower shutter or if a faster shutter is worth some added noise etc.
Guy
Regards, Graeme
The aperture numbers, f2.8, f4, f5.6, f8...etc. (known as f-stops) are multiples of the square root of two. If you notice, every other one is a multiple of two. They represent a ratio between the area of the aperture and the focal length of the lens. The apertures represented by these f-numbers therefore are equivalent in lenses of different focal lengths. Changing the focal length alone will not change the exposure. The lower the f-number, the larger the aperture. Lowering the f-number by one stop increases the area of the aperture by a factor of two, doubling the amount of light passing through it. (I think perhaps they are called stops because the aperture ring on the lens stopped with a click at each full f-number. Canon EOS lenses don't have an aperture ring.)
To keep the same exposure, you must change the shutter speed accordingly. If you double the area of the aperture (enlarge the aperture by one stop) then you must cut in half the length of time the film or sensor is exposed, that is, you must change the shutter speed from say 1/125th to 1/250th of a second.
You use the aperture and shutterspeed to control elements of the photo - aperture for more or less depth of field, shutterspeed for freezing or blurring motion or to reduce the softness of an image due to camera shake. Sometimes you must compromise, sacrifice depth to stop action, for example.
The ISO rating represents different sensitivities of film or digital sensor. With film you must change the roll of film to change the ISO. With the advent of digital photography you can vary the ISO with each shot. This will allow you to mitigate your compromises between aperutre and shutterspeed. Each ISO number - 100, 200, 400, 800 - is double or half the one next to it. ISO 200 is one stop faster than ISO 100; ISO 400 is one stop faster than ISO 200. (The term faster means it will let you use a faster shutterspeed for any given aperture.) Higher ISOs generally have more noise or grain, though the noise or grain at ISO 400 may be an acceptable compomise if it allows you to use the aperture and shutterspeed that you need to make the photo.
In your swimming duck example, you could have increased your shutter speed by one stop from 1/160th to 1/320th of a second, without changing your aperture, by increasing your ISO rating by one stop. If you were shooting at ISO 100, then ISO 200 probably would have been satisfactory. If you were shooting at ISO 400, then ISO 800 may have had too much noise - that can be subjective. From the comment you received it would seem that the swimming duck was sharp enough at 1/160th, so in that particular case a higher ISO and hence a faster shutterspeed wasn't necessary.
I try to keep my ISO as low as conditions will allow. When I was shooting film I used film rated at ISO 100 and occasionally would push it to 200. I didn't like the look of the grain of higher ISO films. Now with digital, I still usually shoot at ISO 100, or ISO 200 if need be, and seldom at ISO 400.
To answer your question, the difference between shooting at ISO 200, f8 at 1/500th and shooting at ISO 400, f11 at 1/500th would be increased depth of field and increased noise, either of which might or might not be noticeable. But basically, in terms of exposure alone, they would be the same.
Hope this helps
All of the above is helpful & correct.
However, your question concerned books about explaining exposure. is ( in my opinion ) to get a hold of John Shaw's book: Nature Photography Field Guide . John explains exposure better than anyone I have ever heard ( or read).
Guy's & Kent;s replies were right on too. They "get it".
I recenly purchased my 1st Digital SLR ( Nikon D200). I feel like I can speak for Guy & Kent in saying, " I am glad I learned on film".because sooooooooooo many principles of digital photography is based on the "old fashioned" film principles.
One you master the exposure thing, and you will , you can feel good about making pleasing images. Ir's not really that complicated, just some books and explanations make it that
way. Guy & Kent couldn't have made it better---( a book guy's?).
I still drive around looking for "medium tone". I was in a restaurant last week and the waiter asked me if I was ready to order. I answered " In a few minutes". he asked if I had questions. I replied" Yes--- it the table cloth medium or - 2/3rds.........? It didn't go over too well.
JG
I'll look into getting that book. Regards Graeme