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Old Jan 29, 2007, 10:46 AM   #1
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According to various reviews, it seems to me that all but the most expensive DSLRs have similar RAW picture quality at ISO 100-400 settings regardless thesensor's nativeresolution. However, at higher ISO settings differences between cameras become more and more visible.

As a novice, I would like to know what are the typical available light shooting situations when higher ISO settings are needed in order to getsufficiently exposed image when shooting:

1) out of hand whithout any kind of shake reduction
2) even with a tripod

In order to narrow my question I'm adding a list of lenses I intend to use:

a) 50/1.8 prime,perhaps 85/1.8
b) 17-50/2.8 (Tamron, perhaps)
c) not to expensive telezoom

Action shooting is not a point of my interest. I intend to postprocess chosen RAW images with computer software for the best results and make calendar sized prints not too rarely, so that's why I'm asking this question, mainly. It will help me to choose the right camera for me.

THANKS in advance!
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Old Jan 29, 2007, 11:02 AM   #2
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mirkoc wrote:
Quote:
As a novice, I would like to know what are the typical available light shooting situations when higher ISO settings are needed in order to getsufficiently exposed image when shooting:

1) out of hand whithout any kind of shake reduction
2) even with a tripod

In order to narrow my question I'm adding a list of lenses I intend to use:

a) 50/1.8 prime,perhaps 85/1.8
b) 17-50/2.8 (Tamron, perhaps)
c) not to expensive telezoom

Action shooting is not a point of my interest. I intend to postprocess chosen RAW images with computer software for the best results and make calendar sized prints not too rarely, so that's why I'm asking this question, mainly. It will help me to choose the right camera for me.

THANKS in advance!
Unfortunately there is no simple answer to your question of WHEN DO YOU NEED HIGHER ISO.

The general answer is: you need higher ISO in order to get faster shutter speeds? You need faster shutter speeds typically for one of two reasons (or both):

1. To freeze motion

2. To compensate for camera shake (i.e. subject isn't moving but you can't keep the camera steady).

So, let's take one extreme: completely stationary subject with enough light for SOME type of decent exposure and you're using a tripod. In this case you would still use a lower ISO value - the camera isn't going to move (assuming a good tripod and remote release) and your subject isn't moving. So even if your exposure takes 3 seconds - so what?

You've already ruled out the other extreme - action photography which requires fast shutter speeds around 1/500. So forget about that.

Which means we're left with the grey middle ground - shooting SOMETHING that ISN't actioin but could still be a person, animal or other animate object.

Now, if you are hand-holding a camera and not employing IS technology the GENERAL rule of thumb is you need 1 / focal length shutter speed to hand-hold and get a steady shot. So a 50mm lens would require 1/50 shutter speeds to hand hold. This is just a general guideline - someone very steady may be able to hand-hold that lens at 1/15 while someone not very steady may require 1/200.

Now, even if you can hand-hold at 1/15 either becase you're very steady, using a tripod or have IS if your subject can move: say an infant or animal - 1/15 may be too slow because the subject doesn't hold still long enough.

Now, ISO, aperture and shutter speed all work hand in hand. For each doubling of ISO, you can double your shutter speed or 1/2 your aperture. Let's say for the sake of argument we fix aperture at a value - f4.0 just for this discussion.

If you have a proper exposure at ISO 100 of 1/15 at f4.

If you increase the ISO to 200 the shutter speed will increase to 1/30

Set ISO to 400 the shutter speed will increase to 1/60; at ISO 800 ss = 1/125 and at 1600 ss = 1/250

Now - what shutter speed do your REALLY need if you have a subject that isn't moving fast but still moving - like a child? Tough call.

So what are you planning on shooting? And why is it that using a flash is not an option in these shots?

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Old Jan 29, 2007, 11:21 AM   #3
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Thank you JohnG!

My main interest is landscape photography (sometimes without a tripod), some portraits and macros.

As for the flash, though I'm not refusing to use one, out of my not too big experience, I believe that images generally look more natural whithout one (please, correct me if I'm wrong).

P.S. I liked your comment on the canoe tipping probability with a camera in it.
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Old Jan 29, 2007, 12:13 PM   #4
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Well for landscape and portrait work I would advise against high ISO due to loss of detail. In fact, for portrait work you'll want to use flash in most instances - if for no other reason, than as a fill flash to remove harsh shadows.

I would also say that if you are serious about your landscape work, you should plan on using a tripod as much as possible. It's your best friend. Besides providing stability, it forces you to slow down and think more about what you're shooting.

I don't shoot macro, but my GUESS is that you don't want to be using high ISO there either as macro is usually about fine details. And, again, depending on what you shoot (animate vs. inanimate) a tripod is your friend. But, I'll defer to those that actually shoot macro to chime in on this one :G


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Old Jan 29, 2007, 12:50 PM   #5
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Well, yes, it's about detail loss at high ISO. According to what I've read online there is a wide spread opinion (it doesn't make it thruthfull one automaticaly, though, and I do not wan't to jump into conclusions) that Canon sensors are better at high ISO.

I'm thinking of buying Canon 400D or Pentax K10. I like K10D very much (so do many Nikonian and Canonian pros too I read) but I'm still waiting for the review at Steve's Digicams to decide. K10D looks more serious camera and I like that. But when I look at both as a system including lens choice, it's getting even more dificult for me (am I wrong in believing that Canon has better earlier mentioned specific lens optins?). Here in Croatia there is also a better backup service for Canon (so they tell me) and I'm also not sure how available are old lenses from Pentax. Do my considerations seem important? Should I listen to my unexperienced inner voice and go for the Pentax? Regards in that directon would be VERY helpfull.

Mirko
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Old Jan 29, 2007, 1:43 PM   #6
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JohnG is absolutely right that detail is king in landscape photography. This is why many serious Pro landscape shoots still use medium or large format (when possible - ones that hike usually don't.) Its because you can make really big prints from them and that the detail is just stunning.

Higher ISO images have less detail. I think we can say that is a fact. I've read several times that Canon has better higher ISO settings than Nikon as well. But I'd go with JohnG here, if you're taking landscape shots you are almost certainly going to care more about detail than shutter speeds.... so you'll use mirror lockup and a remote release (or a timer) and use lower ISO values.

Noise reduction software works during post processing - but its better to get the data up front. And you can, since you're not stopping action.

I don't know about the Pentax lens selection. Canon's is quite good. But then again, I'm baised as I've got 2 Canon DSLRs and have researched them more. They are a bit weak on the wide angle lenses - but they do have good ones, just not as many as people might like.

Eric
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