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08-17-2009, 02:34 PM   #1
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iso vs shutter speed vs arperature

What is the balance that is generally preferred?


For example... iso 800, F22, 1000/s

or iso 200, f22, 500/s

I'd be using a tripod... for both those examples.

I know a larger stop, the more infocus everything would be due to depth of field (correct?)

but aside from noise, is there any real reason why one would choose an iso setting over another and just use shutter speed to compensate?

08-17-2009, 03:38 PM   #2
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Aperture controls DOF, yes.

Shutter speed is used to stop (or show) motion. You would therefore select the ISO that will give you the shutter speed that gives you the effect you are looking for. If I'm trying to freeze fast moving action, then chances are I'm going to use a high ISO to get a fast shutter speed. But if I want the subject to show motion, I'll use a low ISO to get a slow shutter speed.

In your example, what is the subject? If it's a typical landscape, then I would actually use f/22, ISO 100, 1/250 instead of either of the other two.
08-17-2009, 03:53 PM   #3
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The subject is a portrait of a car and a person. Both subjects in frame.

I'm going to be shotting about 15 of these for a local car dealerships website, so I wanna make sure I do it right the first time... seeing as how it's my first paying job. :P
08-17-2009, 03:56 PM   #4
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F/11 or 16 should do it for you in Av mode.

08-17-2009, 04:00 PM   #5
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Hi there.
If you're using a tripod, shutter speed doesn't matter much unless you want to capture the sense of motion, like a waterfall (usu. a slow shutter speed) or moving car (high shutter speed with panning).

Consider making the choice of settings a serial one: start with Av (how much depth of field do I need), then Tv (how fast/slow do I want my shutter to be open), which then determines ISO depending on your lighting conditions.

You would always want to keep ISO as low as possible to limit noise, and only boost it up if you require the extra speed (ie. faster shutter speed, or smaller aperture which means higher f/ value).

Hope this helps.
08-17-2009, 04:02 PM   #6
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Just saw your reply.
Will you be using fill flash? Are you taking the portrait in full-sun/indoors?
This changes how you'd approach the shot.
08-17-2009, 05:50 PM   #7
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I'm shooting outdoors during the early afternoon (12:00 - 2:00)
08-17-2009, 07:31 PM   #8
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Then you wouldn't have to worry about ISO - just keep it at 100, set to Av mode and have f/8 or so set for the shoot - the camera should do the rest - though if you find slight under-exposure (my guess is this will happen because of high contrast), which you'll need to compensate with a small boost in EC.

But I'd also suggest a fill flash of some sort (wireless or even on camera) to boost the light on the subjects and avoid the midday sky from killing the look of the image, though this is another skill in itself. If not considering fill-flash, perhaps a circular polarising filter with camera oriented away from the sun to deepen the blue in the sky may help.

All the best in that.

08-17-2009, 09:02 PM   #9
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Heres a preliminary of what I shot today.

I'm shooting in Raw+, so I get both.

Might give you a better idea of what I'm working with.
08-17-2009, 09:10 PM   #10
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QuoteOriginally posted by Wired Quote
What is the balance that is generally preferred?


For example... iso 800, F22, 1000/s

or iso 200, f22, 500/s

I'd be using a tripod... for both those examples.

I know a larger stop, the more infocus everything would be due to depth of field (correct?)

but aside from noise, is there any real reason why one would choose an iso setting over another and just use shutter speed to compensate?

Wired,

OK, here's are the basic ideas.


What you control

You control three SETTINGS on your camera: aperture (same as f-stop), shutter speed, and sensitivity or ISO. Metering mode and exposure compensation aren't "settings" in the normal sense, although they're important too.

You also control several other things that aren't "settings" but are really important factors in a good photo: the focal length of the lens; how far you stand from the subject or center of interest in the photo; where you point the camera and how you frame the shot; when you click the shutter (somewhat less obvious than you might think and worth mentioning). You control the focal length either by choosing a particular focal length prime or by adjusting your zoom. Distance from the subject is very important for depth of field. I'm going to ignore all of these (although I will come back to distance from subject).

Now, back to the settings.


Aperture

A larger aperture DECREASES depth of field - it doesn't not increase it. By "larger aperture," I am thinking literally of the open part of the aperture. F/2.8 is larger than F/16. Remember, THESE ARE FRACTIONS. 1/2 is larger than 1/16th. Depth of field isn't exactly the same thing as "focus" as you seemed to imply. Just because you use f/16 doesn't mean that you don't have to focus the camera carefully! You can have lots of depth of field - but still have the entire camera out of focus OR blurry because you didn't hold the camera still while shooting.

NOTE about aperture that it's not the sole determinant of depth of field. Focal length and especially distance from the subject really make a big difference, too. If you're shooting at 40mm from a distance of 3 ft at f/2.8, depth of field will be quite shallow: you might be able to get the person's eyes in sharp focus and have their ears somewhat blurry. Using the SAME lens and focal length and the SAME APERTURE but stepping back 15 ft, you'll have quite a bit of depth of field. So when you think "large aperture = small depth of field," keep in mind that this is relative to a given distance from the subject.

In the kind of photography that I do now (portraits and weddings), aperture is usually my first consideration, for one of two very different reasons. I shoot a lot in low light and therefore find myself needing to open up wide to f/2.8, or f/2 or f/1.8 or even f/1.4 depending on the lens I'm using, because I need to get as much ambient light as possible to take a photo at a reasonably fast shutter speed. When there's more ambient light, especially if I'm doing a formal portrait, I may have the luxury of setting aperture simply for depth of field. And if light is good, I'm not always looking for wide apertures like f/2.8: sometimes I want the opposite.

NOTE that you don't usually want to stop down much past f/11 or f/16. You get more depth of field, true, but at some point most lens begin to be harmed by lens diffraction. Another consideration is that most lenses have a sweet spot somewhere in the middle of their aperture range. SO if you aren't primarily concerned about reducing depth of field and you just want the sharpest, clearest image possible, you will often find it somewhere around f/5.6. (This varies from lens to lens!)


Shutter speed

If the subject is static - say, a mountain landscape - and if, further, you're using a tripod, then shutter speed may not matter too much in itself. You can worry then about the aperture (for depth of field) and set the shutter to whatever it needs to be for a correct exposure.

But if the subject is moving (and the subject is ALWAYS moving slightly, unless it's a mountain), then you want a fast shutter speed to freeze movement. Sometimes it's nice to find a shutter speed that's in the middle somewhere, where you can freeze parts of the photo and not others. I took a picture last night of my dog. The dog's body wasn't moving much and the slow shutter speed (1/20th sec) was sufficient to freeze the dog's body, but not her tail - and the blurry tail is a nice effect. (Picture here.) Usually if you're shooting sports, you want a fast shutter speed to freeze movement - say, 1/500th sec. Shooting a waterfall, the common approach is to slow the shutter speed so that the water gets a smoothed-out, flowing look.

Shutter speed can also be used to diminish the influence of camera movement. This matters mainly if you're shooting handheld, and is most important when the focal length is longer.


It's never really either one or the other

Often either aperture or shutter speed will be your FIRST consideration. But it's always important to be aware of BOTH shutter speed and aperture.

You would not want to set the aperture to f/16 for maximum depth of field and fail to notice that this meant your shutter speed was now set automatically to 1 second, because your picture will almost certainly be blurry either from subject movement or camera shake!

Conversely, if you're trying to freeze action while shooting a football game, shutter might be your first priority, but if you're too close to the action and shooting with a wide aperture, you might not have enough depth of field to get the whole line in focus as you want. But remember that distance from the subject increases depth of field for the same focal length and aperture; since you're usually shooting sports and (say) ballet from a distance, you usually have a good bit of depth of field even at your widest aperture.


ISO or sensitivity
The noise produced by high ISO photos occasionally lends an element of "mood" to a photo. But it is as close to a hard and fast rule as you get in photography that, other things being equal, you want the ISO to be as low as possible. LOW ISO = less sensitivity. Noise is not the only disadvantage of higher ISOs: more noise necessarily means less sharp details. Be aware that you can more easily ADD noise in post production than remove it. I shoot a lot between ISO 400 and 1600, in fact, the average ISO of my shots is probably around 500-600. That's because I do so much low-light photography and I don't have any choice. If I had a choice, I'd rather shoot everything at ISO 100-200.


Responding to your specific examples

You said you'd be shooting in early afternoon, and the examples you asked about all included f/22. I'd stay away from f/22 unless I had no choice. As I said above, most lenses begin to produce noticeably inferior results due to diffraction when the aperture gets very small. So increase the shutter speed. ON K10D/K20D you can go to 1/4000th sec which is pretty good for nearly any kind of shot.

The other thing you should do, if you're worried about getting the absolutely maximum depth of field, is read about hyperfocal distance and learn how to calculate it. It's not simply the case that "f/16 produces N ft of depth of field". It depends WHERE you focus.


Hope this helps.

Will
08-17-2009, 10:20 PM   #11
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Will, that did help, but it went into the basics a lil more than I needed.

I guess I got my aperture larger/smaller mixed up a bit. But I got the general idea for shutter speed/ISO. Which is primarily what I was trying to figure out if there is a benift of shotting for priority for shutter over ISO when you got lots of light to work with (outdoors for example).

I usually shoot with aperture priority primarily because I also do mostly low light work... I also will commonly use ISO 800 and then set shutter accordingly.

But outdoors is a new world to me... and so instead of having a wide open aperture, I thought closing it up to get MORE things in focus (which is what I ment), and since I'm pretty much shooting two subjects, both I want in focus... I'm assuming a smaller aperture would help in that manner.


So in a nutshell, for my current task... I would be better off setting ISO to 100/200 range (does the 200% D-range feature really make a huge diff?), set my aperture for something wider than I currently am, and then set shutter accordingly for proper exposure.


The shot taken above was shot at iso 800, F22, and I can't remember which shutter speed off hand...
08-18-2009, 03:18 AM   #12
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D-range attempts to preserve highlight detail in high contrast situations - have a read about it in the manual.

Bottom line is keep ISO as low as possible in every shot as long as the shutter speed is fast enough to handhold or freeze action if required. Otherwise, if needing a slower shutter speed or if using a tripod, you have more room to manoeuvre and keep ISO low.
08-18-2009, 06:54 AM   #13
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If you are shooting at noon time, it doesn't flatter the subject as it produces shadows under the eyes or brow because the sun is just above subject.
You should bring a reflector for fill light of the subjects face.
From your example, you can already see the shadow under the eyes and it doesn't look good.
Put in a fill flash or a reflector would be more desirable.
It also makes you look like you know what you are doing unlike just lugging or using your basic flash.
More gadgets..looks more pro..hehe
Good-luck on your first project!
08-18-2009, 06:58 AM   #14
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If you are shooting dark colored cars too (they can be reflective), be aware of your reflection on the car (you might not be aware of it at times until it's too late).
You might just end up in the pictures you are taking.
Anyway, mine is a bit off topic but kinda related so I hope my posts are ok.
08-18-2009, 07:29 AM   #15
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QuoteOriginally posted by Wired Quote
Which is primarily what I was trying to figure out if there is a benift of shotting for priority for shutter over ISO when you got lots of light to work with (outdoors for example).
As I said, there is (almost) ALWAYS a benefit to dropping the ISO as low as you can get it.


QuoteQuote:
I usually shoot with aperture priority primarily because I also do mostly low light work... I also will commonly use ISO 800 and then set shutter accordingly.
Have you tried using auto-ISO? If you use Av or (on the K10D/K20D or K-7, P = hyperprogram), auto-ISO will help you keep the ISO as low as possible. If you're used to shooting in M, then switch to TAv.


QuoteQuote:
But outdoors is a new world to me... and so instead of having a wide open aperture, I thought closing it up to get MORE things in focus (which is what I ment), and since I'm pretty much shooting two subjects, both I want in focus... I'm assuming a smaller aperture would help in that manner.
Yes, but don't go anywhere near f/22 unless you're desperate! I've shot thousands and thousands of pics in the last year and I'm pretty sure not even 1% of them were at f/22.

When I want more depth of field I either (a) step away from the subject and/or (b) calculate the hyperfocal distance and/or (c) stop down the aperture, but almost never beyond f/11 or f/16.


QuoteQuote:
So in a nutshell, for my current task... I would be better off setting ISO to 100/200 range (does the 200% D-range feature really make a huge diff?), set my aperture for something wider than I currently am, and then set shutter accordingly for proper exposure.
Again, you will almost always be better off keeping the ISO at 100-200, if that low ISO allows you to get the aperture and shutter speed that you require. I would have taken that shot of the guy and the car at ISO 200 or perhaps 100. (Probably 200, because I usually leave the d-range feature enabled.)

Does D-range make a huge difference? Not in my experience. I use it anyway, because there's also not a lot of difference between 100 and 200, most of the time, especially if the light's good.


QuoteQuote:
The shot taken above was shot at iso 800, F22, and I can't remember which shutter speed off hand...
Well, it's definitely not a disaster! I'm a firm believer that whatever works is okay, at least in theory. But let's talk theory about how this photo could be made even better.

Looks like a sunny day, so let's start with the "sunny 16" rule: in bright sunlight, at f/16, ISO should be the same as (the reciprocal of) the shutter; for example, f/16, ISO 200 and 1/200th sec.

Now that shot doesn't look like it's a BRIGHT sunny day, and I would not have felt the need to stop the aperture down further than, oh, f/11. So I'd probably have shot that around f/11, ISO 200, and 1/200th sec. If that produced an underexposure, I'd adjust the shutter a little first, and then perhaps open the aperture to f/8, before moving the ISO higher than 200. The car wasn't moving, the guy wasn't moving, you didn't need a fast shutter for this shot. And f/8 is already going to give you a fair bit of depth of field. According to the DOFMaster online, shooting 35mm focal length at f/8 at a distance of 15 ft from the point you're focusing on will give you depth of field extending about 10 ft in front of the subject and 35+ feet behind. Except that the background even beyond that distance is NOT in this case going to blur badly - this isn't f/2.8 at a distance of 2 ft! And if it was terribly important to have the Ramada Inn sign in the back of the shot tack sharp, too, well, I think I'd take the trouble to calculate the hyperfocal distance before stopping down past f/16.


In summary:
  1. Always keep ISO as low as possible, preferably 100-200, never higher than 400. Main exception: there's not enough light to get shutter speed fast enough to take the shot without blur.
  2. Avoid the lens's smallest apertures - don't go beyond f/11 or f/16 unless you're desperate.

Will
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