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Discussion Starter · #1 · (Edited)
In an earlier thread, discussing camera lenses I suggested that the OP set her camera to AV (canon's designation for Aperture Preferred mode), and then set the aperture at F:5.6 (the lens under discussion's wide open setting at max zoom). I did not, however elaborate on why I would choose those settings. Below is the explanation of my thinking when making that recommendation.

Exposure is controlled by the relationship between shutter speed and aperture (the opening in the lens that controls how much light can pass through in a given amount of time). At any given ISO it takes a specific quantity of light to give you a proper exposure. That light can enter the camera over a short period of time through a large opening, or over a longer period of time through a smaller opening. Stopping action takes a fast shutter speed (large opening, short period of time). Shutter speed controls period of time, aperture controls size of opening. In order to be sure that I am getting the fastest shutter speed possible that will give me a proper exposure under the available lighting conditions, I want to be sure that the opening in the lens is a big as possible, therefore, I shoot action on AV and set my aperture wide open (lowest number on the aperture scale).

If you shoot P (program) (as many folks do), the camera doesn't know what you are trying to do so will use an algorithm that adjusts both shutter speed and aperture in alternating steps to give you a correct exposure; it won't know that you are trying to freeze a dog running at nearly 30mph, so may not choose a wide enough aperture to give you a high enough shutter speed. As an example, if your camera (set on P) decides that the correct exposure can be obtained with the following settings: 1/100 sec at F:16, that shutter speed is too slow to stop action. You would get the same amount of light to the sensor with the following settings: 1/1000 sec at F:5.6 or 1/2000 @ F:4, or even 1/4000 @ F:2.8. Program won't give you any of those settings. When I am shooting action, I ALWAYS, AWAYS shoot AV so I can choose a wide aperture thus achieving the fastest shutter speed possible under the prevailing lighting conditions.

You might think that if you need a fast shutter speed to stop action you should use TV (canon's designation for the mode that allows you to set the shutter speed) and then set the shutter speed high enough to stop the action and let the camera choose the aperture. However, let's say that you determine that when your dog is running full out across in front of you, you get perfect action stopping at 1/2000 sec and luckily the light is sufficient to give you a correct exposure at 1/2000 sec at F:5.6 (which just happens to be your lens's maximum aperture). Perfect. The Gods are smiling on you today. Then (alack, alas) as you shoot, a cloud passes over the sun reducing the light such that you need to be at F:4 (a full stop bigger than your lens is capable of) at 1/2000 sec to achieve a correct exposure. You are going to be under exposed (drat!!). If you had set the camera on AV and chosen F:5.6 (wide open) when the light was perfect you would have been at 1/2000 and all your shots would stop action, but when the cloud reduced the light, the shutter speed would slow down a bit (now F:5.6 @ 1/1000) but still probably stop action most of the time and also achieve a proper exposure.

That's why I shoot action in AV, set my aperture (almost always to wide open) and let my shutter speed "float".
 

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Great post. I for one have a lot to learn about operating that Canon. Can you make this thread a tutorial for taking high quality pics??? :p:p:p
 

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I agree with HPL, and that's how I shoot too.

One addition to that and one reason you may not want to go wide open if you don't need to in some situations.

If you have a camera or a lens that is not as high end, the auto focus may not be quite as fast and you might get lots of shots where you just miss the focus (dog coming toward you with head blurry and tail tack sharp).

A wide open aperture is going to give you less depth of field - That means the range of distances from the lens that will be in focus. If you close down the aperture a bit, you get a deeper in focus area, so if you miss the focus a bit, you're less likely to end up with the head of the dog coming toward you out of focus and the tail tack sharp. The trade off is you need more light to get the shot, or a higher ISO setting.

Good equipment and experience will lessen that as an issue, but it's something to consider. It's also something to consider from an artistic aspect. Usually, I prefer that the subject be in focus and everything in the background blurred out. A wide open aperture (low aperture number) is how you get that. If on the other hand, you want the gun station in the background to be in focus as well as the dog 20 yards closer to you, then you need a higher aperture.

One other consideration is ISO Setting. If you get familiar with your camera, you'll get a pretty good idea of how high you can go on this and what the tradeoffs are. If you go with a 100 ISO setting, you're not going to get much grain. If you go with 2000, you're going to get a lot more grain - probably too much - it makes your shots look grey and you can't get them very sharp at all. You can improve some of this with post processing noise removal, but that's never as good as it could be if you didn't have to deal with it. Once you know your camera, you can make decisions on the ISO that you know will give you a good enough shot for your purposes. If I can, I shoot at 100, but often light doesn't cooperate that well - to give you the high shutter speeds and a 100 ISO. So knowing how high you can go and still get a nice shot is important, and that depends on the camera body generally.
 

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Some great info from HPL and Jerry. Just to add little to the ISO..... I shoot Nikon, and find the Auto-ISO to be a very useful feature. I also shoot aperture priority, but I typically like to shoot working dogs in the f/4-f/8 range. It gives a little more depth of field than a wide open f/2.8, and even the best Nikon and Canon primes are usually a touch sharper stopped down a stop or two. Blurred background, while directly related to aperture and depth of field, is also very much a function of distance between subject and background. An isolated dog at a relative close distance, will have a blurred background when shot with a telephoto lens, even at a smaller aperture.

By shooting Auto ISO with Aperture priority, you can still set your aperture, but it also allows you to set a minimum shutter speed, and a maximum ISO value. The camera will float the ISO to reach shutter speed. What I find is the camera will usually select a lower ISO than I would have set, because I always tend to bump ISO to be sure my shutter speeds stay up.

All this assuming you have decent light. There are times where f/2.8, ISO 6400 won't cut it!
 

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Thanks to all you folks. This kind of info is priceless. My lovely wife had bought me a Canon Rebel T3 or T3i (can't remember which) and being a novice, the camera's been spending the majority of its time in the full AUTO mode. Now I have some understanding how to go about selecting and using some of the other functions.

David
 

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Discussion Starter · #6 · (Edited)
I would not disagree with anything Jerry or Mountain Duck have said. I should say that I am shooting cameras that are about 3 generations old and so don't have the ability to let my ISO "float" and most of the time I don't feel that I get acceptable quality for my purposes with my equipment above 400 ISO. That being said, the newer equipment is apparently capable of producing very good results with low noise at higher ISOs which allows one to shoot at tighter apertures which lets you fudge on the focus some.

When it comes to the effect of ISO on picture quality (and actually when it comes to image quality overall) to some extent, what constitutes "acceptable quality" depends on what the intended end use is. Computer monitors really have very poor resolving ability compared to your camera sensor or photo printer so if you will never do anything with the image but share online, you can get by with lower quality than if you intend to make big prints or want to have it published in a magazine or calendar or such. If you are going to print the images, the larger the print, the higher quality the original image needs to be. What looks sharp at 4X6 may prove to be completely out of focus and loaded with noise at 16X20 (or even 8X10).

In the discussion about shutter speed vs aperture, it was pointed out that tighter apertures although requiring slower shutter speeds can help with focus by increasing depth of field (the area between the closest point of acceptable focus and the farthest point of acceptable focus). The wider the aperture (lower F:#), the shallower the depth of field; also the closer you are to the subject, the shallower the DOF, and the longer the lens the shallower the depth of field at any given distance and F:number.

When photographing moving subjects, the direction of movement has a significant effect on what it takes to get a sharp image. Subjects moving across the frame will require higher shutter speeds to stop the action than those moving at the same speed directly toward or away from you. You may need more depth of field to reliably achieve accurate focus on one moving toward or away than you would for one moving across the frame. So, if the subject is moving across the frame, one might want to select for shutter speed (still AV, but very open aperture) and if moving toward or away one might select for depth of field (again AV but tighter aperture and slower shutter). All these considerations should factor into what camera settings you choose. I find that the AV mode is the one that best allows me to make these decisions. I should also say that I went back and looked at the meta-data for the photos I have recently posted of my dog running and pouncing in the water and all of those shots were shot wide open. When I shot those images I had a 300mm F:2.8 L series lens on loan and actually shot those images at F:2.8, many at 1/4000 to 1/8000 of a second. Those shutter speeds are well above what is necessary to freeze the dog so I probably could have shot the images at F:4 or even F:8. I shot over a hundred images in each session to get fifteen or twenty (per session) that I thought were worth saving and perhaps had I had a greater depth of field, my average would have been higher.
 

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Hugh, Wow, that is a ton of good info. I, however tend to set my aperture according to what I want the image to portray. That said, each lens shoots best (sharpest focus) at certain aperture settings. Love the way you are teaching the masses! Keep up the great work.
 

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Discussion Starter · #9 ·
Hugh, Wow, that is a ton of good info. I, however tend to set my aperture according to what I want the image to portray. That said, each lens shoots best (sharpest focus) at certain aperture settings. Love the way you are teaching the masses! Keep up the great work.
Thanks Tony!
I completely agree with you, with an understanding of all the ramifications of various shutter speed/aperture combinations, one can make better decisions. It has been my experience that often having a basic formula helps many folks move up from Auto to one of the more advanced modes. Once folks start taking control of some of the settings, they may begin to understand how different shutter speed/aperture combinations affect the look of a photo.

I also went back and looked up the tech data for the photo in your avatar and you don't say what mode you were in, but the exposure was wide open F:2.8 @ 1/2000 sec using a much better camera than what I shoot, but the same lens that I used for those shots of my dog running on and pouncing in the water.

Do you remember if you were focus tracking on that photo or if you pre-focused on the dummy?
 

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Pre-focused on the dummy Hugh.

Thanks Tony!
I completely agree with you, with an understanding of all the ramifications of various shutter speed/aperture combinations, one can make better decisions. It has been my experience that often having a basic formula helps many folks move up from Auto to one of the more advanced modes. Once folks start taking control of some of the settings, they may begin to understand how different shutter speed/aperture combinations affect the look of a photo.

I also went back and looked up the tech data for the photo in your avatar and you don't say what mode you were in, but the exposure was wide open F:2.8 @ 1/2000 sec using a much better camera than what I shoot, but the same lens that I used for those shots of my dog running on and pouncing in the water.

Do you remember if you were focus tracking on that photo or if you pre-focused on the dummy?
 

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Discussion Starter · #11 ·
Great post. I for one have a lot to learn about operating that Canon. Can you make this thread a tutorial for taking high quality pics??? :p:p:p
Pre-focused on the dummy Hugh.
If I can find some water, I may go give that a try this weekend. The stuff I have previously posted was focus tracked.

To acknowledge James' request, will also try to shoot some stuff showing the effect of varying shutterspeed and aperture (all shot in aperture preferred, of course).


Now if we can get Todd Caswell and some of the other good shooters to join in....
 

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I forgot to mention, Hugh, that I use Hyperfocal distance for that set up.
 

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Discussion Starter · #13 ·
Tony,
I deleted some stuff from my inbox so give it another try please.

HPL
 

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Discussion Starter · #15 ·
Hyperfocal distance is the point at which if you are focused, you have the maximum depth of field at any given F number (not sure about the grammar in that sentence). If you are focused at the hyperfocal point, everything from that point to infinity will be acceptably sharp and the area of acceptable focus will also extend (I believe) about 1/3 the distance back toward the camera. The hyperfocal point gets closer as the F# goes up. The formula for calculating the hyperfocal distance is HF = lens length in mm squared divided by the (f# times the acceptable circle of confusion (often something like .03mm). Once you do the multiplication and division, you add the lens length back to that number. Clear as mud?

It is explained on numerous sites on the net.
 

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Interesting.

So would the reason you use that distance because you're going to get tack sharp focus on the focal point, and everything beyond that will be in acceptable focus, and even in front a bit?
 

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Discussion Starter · #17 ·
Interesting.

So would the reason you use that distance because you're going to get tack sharp focus on the focal point, and everything beyond that will be in acceptable focus, and even in front a bit?
Well, actually, the hyperfocal point is used most frequently by landscape photographers. If you plug numbers into the formula, you will soon discover that when using a telephoto lens, the hyperfocal point is quite distant. If you were using a 300mm lens on a digital SLR and had the lens set at F:4, the hyperfocal point is around 3900 (yes, 3900!)ft. (this is based on a circle of confusion of 0.019mm)

300mm X 300mm = 90,000mm divided by (4 X 0.019) = 1,184,210mm = 3886 ish feet

If you focus on the hyperfocal point your depth of field will extend from 1943ft to infinity (not particularly useful as far as I can see).

That means that the hyperfocal distance is pretty useless when using a telephoto, however landscapes are often shot using wide angle lenses at very tight apertures.

If you are using a 24mm lens stopped down to F:16, the hyperfocal distance is about 6ft. If you focus at that point, the area of acceptable focus will be from about 3.15ft to infinity. For a landscape photographer, that might be very useful.

Just so you don't think that this is stuff I deal with all the time and was able to just pull out of my mind, I went back and found a DOF calculator on the net http://www.dofmaster.com/dofjs.html. It's a cool site and will calculate DOF for just about any camera/lens/F:#/distance combination.
 

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So how does Tony set up that shot?
 

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Throw a bumper out there and focus on the bumper, pin the shutter untill the dog is out of focus and do it again.... and again and again.
Dig. photog is a game of #numbers and shutter clicks. Hold the button down and let it ride............ The main reason photography has been cheapened in the past few years. But it is what it is...................
 

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Discussion Starter · #20 ·
So how does Tony set up that shot?
I believe to some extent what Todd said. he has explained in an earlier post that he positions himself and the deke and then has someone run the dog for him. Search for his posts. There are several and they are very informative.

I believe that Tony misspoke when he referenced the hyperfocal technique. I believe that what he meant was that he prefocused and pre-checked his depth of field finding a point that would allow both the deke and the point where he anticipated the dog being to be in acceptable focus.

Perhaps he will clarify.

For the photos I have posted, I used the focus tracking method where I focused on the dog as he started his run and let the camera maintain focus, then, as the dog approached the target zone, I depressed the shutter release and let the drive shoot a string of frames. Perhaps less elegant, but very effective.
 
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