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 Post subject: ISO
PostPosted: Sat Jul 02, 2011 12:14 am 
My question is regarding ISO... all the high end cameras like i am looking at D7000/EOS 60D have the ability to increase ISO from 100 to 6400 (plus H1
and H2 equivalent to ISO 12,800/25,600)

Then when reading some tutorials I am reading to keep ISO low as higher ISO's reduce quality

"http://www.dslrtips.com/workshops/How_to_take_photos_at_night ---Increasing the sensitivity will however reduce your picture quality and may still not give you a quick enough exposure to handhold. So stick to using a tripod and a low ISO number for the best quality."
/manual_long_exposure.shtml


1. so whats the point of having such high ISO's?

2. how to correctly use ISO?


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PostPosted: Sat Jul 02, 2011 2:27 am 
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The foundations of correct exposure relies on the combination of 3 things: shutter speed, aperture, and ISO. If you're not familiar with these then you need to google them as they're fundamental to understanding photography.

When you select a higher ISO, the sensor signal is amplified. This means that less light is needed to correctly expose an image. An ISO of 200 needs half the light as ISO 100, ISO 400 needs half the light as ISO 200 and so on...

The positives of a higher ISO are that you can select a higher shutter speed (meaning you're more likely to freeze motion (for sports/action), reduce hand shake (for low light shots or telephoto zoom shots) or can choose a higher f-stop (for increased depth of field).

The negatives are a reduction in the picture quality. A higher ISO increases noise or grain in the image, reduces detail, and can make and image looked muddy.

Gordon's reviews allow you to compare different cameras a different ISO settings. Here's the one for the D7000:

http://www.cameralabs.com/reviews/Nikon_D7000/noise_JPEG.shtml

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 Post subject:
PostPosted: Sat Jul 02, 2011 2:29 am 
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Location: St. John's, NL, Canada
Hi Jazzsingh.

You are correct about keeping the ISO low as it does reduce the quality. The degree at which the ISO reduces the quality will depend on the camera. For example, my D200 at ISO-1600 will produce a more grainy photo than, for example, the D300s at ISO-1600.

ISO will allow you to take shots at faster shutter speeds. So basically, having such a high range on the ISO will allow you to take shots with faster shutter speeds in low light conditions.

As far as how to correctly use ISO - keep it as low as you can. If you're getting blurry photos, then increase it unto an acceptable level. ISO and shutter speed are inversely proportional so the higher you set your ISO, the faster you can set your shutter speed to get a correctly exposed photo.

Hope this answers your question.


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PostPosted: Mon Jul 04, 2011 2:35 pm 
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The reason why it is there is for situations where you need the photograph, and having it is better than not having it.

The consumer DSLRs even have expansion, but you have to enable it within the custom functions.

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PostPosted: Mon Jul 04, 2011 4:00 pm 
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As a sort of professional concert photographer, I can only tell you that high ISOs are NOT a gimmick (well, perhaps the ultra high modes on small snesor cameras). In order to capture enough light, I'm often at ISO 1600, and that's with ultrabright lenses.

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PostPosted: Mon Jul 04, 2011 4:36 pm 
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Yes, not a gimmick.

Basically, treat it like a get out of jail free card, within the limits of the camera you're using.

Keep it as low as possible until you need to increase the sensor sensitivity to maintain the shutter speed and aperture you require. Doubling the ISO will give you an extra stop to play with in either shutter speed or aperture.

I use a preset on my D700 to maintain a minimum shutter speed before the camera ups the ISO automatically - anything up to 6400 is perfectly usable if you're exposing correctly. Very liberating!


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 Post subject:
PostPosted: Mon Jul 04, 2011 6:26 pm 
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That said I almost always prefer a noisy shot over a blurry one.

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 Post subject:
PostPosted: Tue Jul 05, 2011 2:52 pm 
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Joined: Wed Nov 18, 2009 5:23 pm
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Location: Boca Raton, FL, USA
As others have mentioned, my system on using ISO is:

Use as little as you can, but as much as you need to get the shot.

I start at low ISOs, and work the aperture & shutter for the shot - if I can't get the exposure I need or a specific shutter or aperture I need, I'll raise the ISO until I can get what I need. I have no qualms about using high ISO, and routinely shoot from ISO200-1600, and quite often at ISO3200 & 6400 as needed. ISO12800 is rare for me, mostly because my camera is not as good at that ISO, whereas it's still very usable at ISO6400.

I agree too with having a preference for a noisy shot over a blurry shot, so I'll use every bit of ISO I need to for my shot.

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