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PostPosted: Thu Aug 21, 2008 8:28 pm 
I watched the night photography video, great information. But there is no mention of ISO. The camera shows 100 ISO, but I'm sure that can't be correct. Any thoughts on this.


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PostPosted: Thu Aug 21, 2008 10:56 pm 
Welcome to the forum. Let me assure you that your eyes didn't deceive you. Regarding ISO and long exposures at night - you use the lowest ISO available to you so that you reduce resultant noise. After all you're aiming to get a long shutter time. It's handholding in low light where you'd want to raise the ISO to get a faster shutter speed to reduce handshake.

I hope this helps.


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PostPosted: Thu Aug 21, 2008 11:31 pm 
Thank you for your response. But now I'm a little confused. I understand the need for adjusting the ISO for handholding, as well as doing so creates noise, but I thought it was a must in dark situations. And ISO's of 100 or 200 were to be used in sunny conditions. Is all of this wrong? Do I use 100 in a dimly lit room while using bounce flash?


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PostPosted: Thu Aug 21, 2008 11:50 pm 
If you're using a tripod, you can use whatever ISO you wish. You only set the ISO high so it is more sensitive to light and thus letting you ramp up the shutter speed.


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PostPosted: Fri Aug 22, 2008 12:25 am 
Now I'm confused. I understand ISO & sensitivity to light, ( & need for a tirpod) but I guess I've been wrong in my thinking as far as dark situations. What would be a norm for a room as I said? My confusion comes in because I've been told to use 400 ISO & up in these situations.


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PostPosted: Fri Aug 22, 2008 12:45 am 
Kay wrote:
Now I'm confused. I understand ISO & sensitivity to light, ( & need for a tirpod) but I guess I've been wrong in my thinking as far as dark situations. What would be a norm for a room as I said? My confusion comes in because I've been told to use 400 ISO & up in these situations.


You should adjust your ISO as you see necessary. If you are in a low-light area, trying to take a photograph without a tripod, you will most likely need to bump your ISO up so that your shutter speed is fast enough so that you can shoot the image hand-held without worrying about camera shake.

When doing long exposure/shutter speeds, you want to put the ISO at the lowest (i.e. 100) so that during the _____ amount of time that the shutter is open, noise sensitivity is as low as possible. This helps with the image quality and the amount of noise present when the shot is taken.

So for example, if you are in a room and you have your ISO set at 100. You might be getting an exposure value of 1/5th of a second at f/5.6 (example). This is quite risky to shoot hand-held. Even with a VR/Image Stabilization system active. So you bump your ISO up to 400. Now you get a exposure value of 1/30th of a second at f/5.6. Much better to shoot hand-held! This is also great if something is moving. At 1/5th, almost everything that moves will be blurred. Now 1/30th is still a bit slow for moving objects, but you get the idea....

So to sum it up, when doing long exposures, keep your ISO at 100 so that your image does not get too grainy due to more light hitting the sensor.

When you need a faster shutter in low-light, bump your ISO up a bit. This might cause some loss in image quality, but at least you will have the image, no?

When outdoors, you will usually have a sufficient amount of light to shoot with. So I suggest keeping your ISO at around 100.

It all comes down to your subject, and your lighting. Just remember to read your shutter speed, and see what you need to do.

Best,
-Sean.


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PostPosted: Fri Aug 22, 2008 2:17 am 
Thanks so much for the info. While I thought I was doing well on the learning curve, I guess I got a little lost in the ISO. :wink: I guess it is back to the books.


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PostPosted: Fri Aug 22, 2008 2:23 am 
Ah, a thought! I hope in the right direction. ISO & shutterspeed work hand in hand, correct. So, (tripod) using ISO 100 (dark) is great for stationary objects, buildings etc, (longer shutterspeed) but to increase the shutterspeed to prevent the blur of say moving people then a higher ISO is needed. Although sacrificing a no noise picture. I think I've got it, I hope....


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PostPosted: Fri Aug 22, 2008 3:49 am 
Kay wrote:
Ah, a thought! I hope in the right direction. ISO & shutterspeed work hand in hand, correct. So, (tripod) using ISO 100 (dark) is great for stationary objects, buildings etc, (longer shutterspeed) but to increase the shutterspeed to prevent the blur of say moving people then a higher ISO is needed. Although sacrificing a no noise picture. I think I've got it, I hope....


ISO and shutter speed work together to an extent yes. The higher the ISO, the faster the shutter speed will be...

You've got it down pretty well. Just remember that you might not need to increase your ISO to get a fast shutter speed. With enough light, you can shoot moving subjects with ISO 100. Again, it just depends on the shot.


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PostPosted: Fri Aug 22, 2008 4:18 pm 
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Yep, further to what everyone's said, just remember that every time you double the ISO, you can use a shutter speed that's twice as fast. So as everyone's said, if you're on the cusp of camera shake, a small boost in ISO can give you the shutter speed you need to avoid it.

But if you're looking at, say, a 5 second exposure at 400 ISO, then you'd get the same exposure with 10 secs at 200 ISO or 20 secs at 100 ISO.

Since all are way too long to handhold successfully and require a tripod, you may as well go with the 100 ISO option to retain the best quality.


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PostPosted: Fri Aug 22, 2008 7:23 pm 
Just to complement what everyone said, remember that long exposures(>10-20 s) will bring some noise into your pictures as well, even with your lowest ISO settings.


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