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ISO vs. Shutter Speed

joe cormier , Jun 01, 2011; 08:14 a.m.

I still am very confused over the selection of shutter speed and ISO. I see the following situation a lot. In Wed. Picks there
is a photo of 2 musicians in b/w. It appears to be a daylight shot. The ISO is set to 800 and the shutter speed is set at 1/800
sec. The photo was taken with a 70-200mm 2.8 lens.

My question is what is the advantage of such a high ISO in combination with such a high shutter speed? It has been
suggested to me that under most circumstances the lowest ISO is recommended to obtain the least noise. Would the shot
mentioned have better results with for example, ISO set at 200 and the shutter speed set to 1/250 sec.? As always, thanks
in advance.


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Andrew Garrard , Jun 01, 2011; 08:43 a.m.

Hi Joe. I would guess one of:

a) The photographer wanted a deliberately grainy look, or
b) The camera was set up to capture fast action (which, admittedly, there doesn't appear to be in this shot - assuming you mean the first of this week's) and the settings were an accident, or
c) It just didn't matter - ISO 800 is reasonably low noise on modern bodies, so maybe the camera was set to ISO 800 knowing it would be "okay" (with the expectation that photos would be taken in low light during the same session), and used in aperture priority.

At ISO 200 there would be slightly less noise/better sharpness (depending on the noise reduction) if the only motion to be worried about was normal camera shake, but - especially at the size presented - whether you'd notice the difference is another matter. Maybe something was moving fast enough to justify a 1/800s shutter speed - if the photographer was in a moving car, the settings worked very nicely!

Leslie Cheung , Jun 01, 2011; 08:48 a.m.

My guess is the photographer wanted shallow dof to emphasis the hand by isolation.

Andrew Garrard , Jun 01, 2011; 08:53 a.m.

Leslie - it's not taken at full aperture, but I think the question mark is more about the very high shutter speed than the choice of aperture. I'd not read too much into it (and I like the image).

Rodeo Joe , Jun 01, 2011; 09:02 a.m.

ISO versus Shutter Speed? I didn't know it was a fight, but my money's on Shutter Speed - he's fast!

Seriously; it's not a competition and there's no contradiction in having a high ISO and a high shutter speed. If you need a fast shutter speed as well as some depth-of-field and the light's not bright enough, then all you can do is raise the ISO. Besides, modern cameras like the D700 can give you an ISO of 1600 or 3200 with almost no visible noise. So ISO becomes just another control in your armoury; and if it wasn't meant to be changed there wouldn't be a button for it, would there?

Matt Laur , Jun 01, 2011; 09:05 a.m.

Here's the photograph in question:

The photographer in question (me!) had just been shooting a bunch of people under a very shady tree canopy, and needed enough DoF to get several faces in focus. That called for a high enough ISO to shoot at f/8 while still having a tolerable shutter speed to freeze subject motion (in those conditions, I got 1/250th or so as long as I was at ISO 800). Done with that, I turned around to get a few quick shots of the swing band playing nearby, and liked the look of the stand-up bass's sculptural headpiece, the player's watch, etc, with the sax man out in front of him ... but I didn't like the very busy background, which would have completely swallowed up those details.

So, to control depth of field and isolate the bass player's instrument and hand, I opened the lens up to nearly its widest aperture, and used it at f/3.2. I don't mind doing that with Nikon's 70-200/2.8, because its bokeh characteristics, even with all of that bright, contrasty stuff going on, are something I know and like well enough.

But because I don't usually like auto ISO and was working quickly, the camera stayed at ISO 800 - and no harm done with a D300 as long as things aren't underexposed. And, as a result, and because I almost always shoot in aperture priority mode, the camera's metering system pushed the shutter speed up to 1/800th in that slightly brighter light - which suited me fine, since that bass player was moving the neck of his instrument around like Fred Astaire dancing with a hat stand, and I really wanted to preserve the details of the scratches, the tuning hardware and the rest, with no motion blur.

Peter Hamm , Jun 01, 2011; 09:24 a.m.

I've shot some very use-able stuff accidentally on ISO 1600, even on my old D50.

Nice shot... who cares how you got it...

Bob Cook , Jun 01, 2011; 09:36 a.m.

Very nice photo and a good explanation. I'm just starting to use my D700 more, and I'll try some higher ISO options.
I'm also a bass player (not a musician, just a player), but I always take my watch off when playing, thinking it will make me "faster." Not likely.

Kent Staubus , Jun 01, 2011; 09:39 a.m.

Depends on what you are after. I often shoot at night, and my subjects move fast. I need a fast shutter speed and the only way to get that is to use high ISO (and wide aperture.) I typically shoot at ISO 400 in bright daytime, and ISO 800 most other times. I usually am after fast shutter speeds with some DoF.
Kent in SD

Andrew Garrard , Jun 01, 2011; 10:08 a.m.

Thanks, Matt - mystery solved! (And, again, nice image.)

In case this information helps anyone: up until very recently I used my D700 mostly in aperture priority, with auto-ISO set to keep the shutter speed above 1/focal length. Due to the inconvenience of changing the minimum shutter speed in the auto-ISO settings, with a zoom lens, I quite often ended up with a shutter speed appropriate for the long end of the zoom even when shooting at the short end - my 28-200mm often ended up at 1/200s even when used at 28mm, for example.

It only recently occurred to me that I was actually better off shooting in manual mode with auto-ISO enabled; that meant I could tweak the shutter speed as the focal length of my zoom changed, just by rotating a dial. What I lose is the automatic change of shutter speed once I bump off the ends of my ISO range - but unless I have widely changing light conditions or am failing to pay attention to the in-finder meter reading, it's usually more useful for me, and means I'm not wasting my ISO whenever I use a zoom lens. I'd use auto-ISO less if there was a convenient way to set ISO explicitly one-handed.

I've spent all day with an Eos 300D accidentally at ISO 800 - and you can see ISO 800 on a 300D. But then I also spent a whole evening on astronomy exposures without realising the camera wasn't producing raw images. And I've taken quite a lot of photos without realising the camera was in manual focus mode, as well...

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