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02/06/2009 01:48:02 AM · #1 |
okay.. so here is my situation.
low light. macro. 1/60 (or so) shutter...aperture. 2.8.
what SHOULD my iso be?
i'm having trouble getting my lighting right, how does the iso affect it?
thanks in advance!
:) |
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02/06/2009 01:54:33 AM · #2 |
| Well, if you HAVE to shoot at 1/60 with f/2.8 then you're ISO is probably going to have to be pretty high. Otherwise, I'd say to keep your ISO as low as possible, especially for macro shots. ISO is basically the "speed" of the "film." The higher the ISO the more you can capture in darker settings, however the film grain is going to be much greater. |
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02/06/2009 02:01:46 AM · #3 |
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02/06/2009 02:04:04 AM · #4 |
| 1600 ISO is probably going to be pretty grainy on the XTi. Why don't you just use a tripod or set the camera on something and lower the shutter speed? |
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02/06/2009 02:11:21 AM · #5 |
well its for an assignment and i can't use the tripod. and i can't go under 1/60.
but it was really low light today, it was rainy and cloudy. I'm going to try again tomorrow. |
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02/06/2009 02:49:04 AM · #6 |
Originally posted by LMA128:
well its for an assignment and i can't use the tripod. and i can't go under 1/60.
but it was really low light today, it was rainy and cloudy. I'm going to try again tomorrow. |
Reflectors are very effective to increase the light for macros. Some aluminium foil will already do. |
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02/06/2009 02:52:37 AM · #7 |
every time you double your ISO you can double your shutter speed for the same aperture.
eg if the "correct" exposure is
ISO 400 1/30 f/2.8
then to get a shutter speed of 1/60 you would need to set the ISO to 800
ISO 800 1/60 f/2.8
of if the "correct" exposure is
ISO 400 1/125 f/2.8
then to get a shutter speed of 1/60 you would need to set the ISO to 200
ISO 200 1/60 f/2.8 or you could reduce the aperture by one stop and keep the ISO at 400
ISO 400 1/60 f/4
Basically you want to have the ISO as low as you can for the shutter and aperture you want to use |
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02/06/2009 02:55:29 AM · #8 |
| If you have to shoot at f2.8 and you want a slow shutter speed like 1/60 you're going to need a low iso, the more light you have the lower the iso you'll need to get that slow shutter speed. Certainly iso 100, maybe 50 if your camera will let you :) |
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02/06/2009 03:10:37 AM · #9 |
| Not sure.. but doesnt XTi show an exposure meter telling you if the scene is under/over exposed based on the chosen metering mode? I am referring to the scale thingy in the view finder. Then you can go into Manual mode and tweak the settings to see that scale. |
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02/06/2009 03:54:26 AM · #10 |
If you set the camera on manual, set the aperture at f/2.8, and rotate the shutter speed dial, when the pointer in the viewfinder's in the middle of the scale the exposure is correct, more or less. Start with the camera at ISO 100. If the shutter speed drops below 1/60, then set it at 1/60 and start changing the ISO upwards to 200, 400, whatever, until the needle centers.
R.
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02/06/2009 04:38:31 AM · #11 |
Originally posted by LMA128:
well its for an assignment and i can't use the tripod. and i can't go under 1/60.
but it was really low light today, it was rainy and cloudy. I'm going to try again tomorrow. |
You always want to aim to have as low an ISO number as possible - the lower the ISO, the better the image quality.
If you are shooting outdoors, at F2.8, you should be getting loads of light in, even if it is cloudy and rainy. With a shutter speed of just 1/60, I wouldn't have thought you would need to push the ISO too high?
If your assignment is to take the pic with the aperture and shutter on these settings, then take a picture of your chosen scene at all the available ISO's and then compare how your results come out. Easy enough with digital...
On one of your posts you say you are not allowed to go below 1/60. Do you mean you can't have a slower shutter (Lower number) or a faster shutter (Higher number)? |
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02/06/2009 06:01:26 AM · #12 |
Speaking from experience, ISO 800 and ISO 1600 on the 400d/Rebel XTI are pretty unusable unless you are intentionally going for a noisy look...
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02/06/2009 07:20:57 AM · #13 |
| Lots of good advice here, but I'd try to keep the ISO as low as possible, and if you can't use a tripod I'd try to get some more light on the subject. Try a reflector (even aluminum foil on cardboard can help) or a flashlight or whatever else you can find. |
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02/06/2009 07:36:31 AM · #14 |
| Just an additional FYI... if you go the aluminum foil reflector route, make sure you crinkle the foil up, otherwise the reflected light will be very harsh. You can also use white paper. |
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