Posted by Tom Hilton on October 3, 2011 at 7:27 AM
I'm an old (film) dude, so I'm always thinking the lowest ISO is the best way to go.
I have seen that ISO's of 200 - 400 are the optimum for the lowest noise...
so should I be using 100 - 200 or 400 .... my prints go to 20x30 so I'm looking for sharpness also.
Thanks for amy suggestions...
Tom H
Posted by Jim Bullard on October 3, 2011 at 8:35 AM
Digital cameras have a native or best ISO. It's usually low but not necessarily the lowest. It usually around 100-125 in my experience.
Tom, while in practice sensitivity (ISO) has a similar effect in digital capture as it does with film, it helps to understand why in order to pick the optimal setting. The simple answer to your question is that each sensor has an optimal setting. For Canon DSLRs, it is generally ISO 100. Many Nikon DSLRs perform best at ISO 200, etc. This setting works best in most situations, but not all.
In film, low ISO is generally correlated with smaller grain structure, resulting in smoother images (less visible grain). In the digital world, noise is a result of the quality of sampling (i.e., how accurately the sensor can measure the amount and color of light at each of its photosites). If the measurements are inaccurate, adjacent photosites may appear different, resulting in a noisy look.
The quality of sampling depends on the amount of light (literally the number of photons) available and the physical size of the photosite. In bright light, for example, where the photosites have enough data to produce accurate measurement, ISO 400 may appear cleaner than ISO 100 might in a low light situation.
When working in dim light where sampling may be inaccurate, longer exposures may help the photosites gather enough light to produce accurate results. Unfortunately long exposures are also susceptible to electronic noise resulting from the sensor itself. The two should be balanced for optimal results. This is also why digital sensors don't do as well as film in very long exposures.
Changing the ISO setting on your digital camera doesn't actually change the sensitivity of the sensor. Instead, it tells the camera's computer to multiply the sampled values. At a given exposure time, ISO 100 and ISO 400 use the exact same data from the sensor. At ISO 400 the numbers will be multiplied by 4 to produce the final image. Sampling issues will therefore be magnified at higher ISO settings. At a given scene, though, ISO 400 will require 1/4 the exposure time, giving the sensor less time to sample light, and further exacerbating any potential issues.
Ultimately, like film, you should use the lowest setting that will result in a successful image. If shutter speed is not a concern - stick with the base ISO setting for your specific camera. If you need a fast shutter speed to freeze motion, or if light level is so low that the base ISO requires a very long exposure (30 seconds or more), consider a higher setting.
Guy
Posted by Keith Bauer on October 3, 2011 at 8:50 AM
As Jim noted, there is a base "native" ISO for digital sensors. Most Canon cameras have a base ISO of 100, many Nikons begin at 200. If your goal is clean, large prints, then I would suggest using the lowest ISO you can for the lighting conditions and subject matter.
Posted by David Bostedo on October 3, 2011 at 8:53 AM
Some cameras lowest ISO is 200 - higher end Nikons in particular. This is almost always the lowest listed ISO. Usually something in the specs or name will indicate if the lower ISOs are below the base ISO (Like they may be called 100Low or something like that.) And sometimes the lower ISOs are created after exposure by the camera processing. Usually this results in a clean image, but may give up some dynamic range or mess with the exposure.
Either way, you will get your best image if you can use the actual base ISO. This will give you the best signal-to-noise ratio, which will also give you the best sharpness.
If you're really concerned about noise, you should also look into Exposing To The Right (ETTR) This means that you expose the image so that the highlights are just short of being blown out, even if this means you're overexposing the image. Then you adjust the exposure back to what it should be when processing your file. In this way, you've gotten the most light possible on the sensor, which will greatly enhance you signal-to-noise ratio and give you the cleanest image.
Of course, if your scene has a big dynamic range already, that might not be of too much use. But it very good practice with digital where you can do it.
Posted by David Bostedo on October 3, 2011 at 8:57 AM
Instead, it tells the camera's computer to multiply the sampled values. At a given exposure time, ISO 100 and ISO 400 use the exact same data from the sensor. At ISO 400 the numbers will be multiplied by 4 to produce the final image.
Just to be clear, this multiplication is a change in the amplification at the pixel or read-out level. (I'd say it uses the same data from the pixels, not from the sensor.) It's not quite the same as capturing an image and then multiplying the values after the fact.
You're right, David, although I would use "photosite" instead of "pixel". Sensor data (RAW) is not mapped to pixels until it is converted post-capture.
Guy
Posted by Tom Hilton on October 3, 2011 at 10:20 AM
Ultimately, like film, you should use the lowest setting that will result in a successful image. If shutter speed is not a concern - stick with the base ISO setting for your specific camera. If you need a fast shutter speed to freeze motion, or if light level is so low that the base ISO requires a very long exposure (30 seconds or more), consider a higher setting.
Guy
That is pretty much what I have always done....
Dang, that was quick and unbelieveably thorough...
Thanks y'all....
I guess I should have mentioned my main camera is a Nikon D300s with a D200 as a backup...
200 is the last number on the readout but it has 3 more lower settings down to 100..
Thanks again for all the information...
Tom H
Things get can get "interesting" when you're forced to move up the ISO scale. I'm not so concerned about results at the low end as at the high end. It would be worthwhile to compare results at the higher end for each of your models if you have more than one, and be prepared to move to the one that performs best when you have to shoot in low light.
For example, our own testing and use has shown that the Nikon D300 turns out better results at ISO 2400 and even 3200 than the D2X can manage at ISO800. A "generation" step in technology from older to newer models certainly made an improvement between those two, even though the 300's cost roughly 1/4 the price of a D2X. The first time I shot them side-by-side was on a commercial aerial shoot early in the morning when I carried the D300 as high speed "backup" to the D2X, and turned out virtually 100% good results from the 300 at ISO2400 and ISO3200 and not a single usable image from the D2X at ISO 800. The client has since used some of the D300 images for wall-sized photos in tradeshow booths and advertising, but I would have been hard pressed to turn out a decent 20x30 from the D2X images.
Posted by Tom Hilton on October 3, 2011 at 11:17 AM
Hank,
I don't usually shoot a lot of low light stuff. But, I was shooting a night high school football game with the D300s and the D200... with the ISO run way up....the images from the D200 were extrenly noisy and poor, the D300s' were great...whatever Nikon did was a heck of an improvement...
...whatever Nikon did was a heck of an improvement...
No kidding!
I've posted this before, but here's a cull from that shoot. It was around 5:30AM, heavy overcast and rain, and I had to shoot in very tight turns at 80 knots through a small triangular window at the "copilot's" seat. It was a very narrow shooting alley between the prop, window frame, wing and float, and I had to be really quick. The framing in this shot went all haywire on me when we hit a sudden downdraft, but there is no noise in those blacks. The D2X shots looked like I was shooting in a snowstorm at 3200 ISO (Hi2), while at 800ISO shutter speeds went waaaaaay too low for the circumstances.
Posted by Tom Hilton on October 3, 2011 at 1:44 PM
That was a challanging shoot for you....
Posted by David Bostedo on October 3, 2011 at 1:52 PM
I would use "photosite" instead of "pixel"...
Good point, Guy. I don't want to confuse the issue further...
Discussion
12 repliesI have seen that ISO's of 200 - 400 are the optimum for the lowest noise...
so should I be using 100 - 200 or 400 .... my prints go to 20x30 so I'm looking for sharpness also.
Thanks for amy suggestions...
Tom H
In film, low ISO is generally correlated with smaller grain structure, resulting in smoother images (less visible grain). In the digital world, noise is a result of the quality of sampling (i.e., how accurately the sensor can measure the amount and color of light at each of its photosites). If the measurements are inaccurate, adjacent photosites may appear different, resulting in a noisy look.
The quality of sampling depends on the amount of light (literally the number of photons) available and the physical size of the photosite. In bright light, for example, where the photosites have enough data to produce accurate measurement, ISO 400 may appear cleaner than ISO 100 might in a low light situation.
When working in dim light where sampling may be inaccurate, longer exposures may help the photosites gather enough light to produce accurate results. Unfortunately long exposures are also susceptible to electronic noise resulting from the sensor itself. The two should be balanced for optimal results. This is also why digital sensors don't do as well as film in very long exposures.
Changing the ISO setting on your digital camera doesn't actually change the sensitivity of the sensor. Instead, it tells the camera's computer to multiply the sampled values. At a given exposure time, ISO 100 and ISO 400 use the exact same data from the sensor. At ISO 400 the numbers will be multiplied by 4 to produce the final image. Sampling issues will therefore be magnified at higher ISO settings. At a given scene, though, ISO 400 will require 1/4 the exposure time, giving the sensor less time to sample light, and further exacerbating any potential issues.
Ultimately, like film, you should use the lowest setting that will result in a successful image. If shutter speed is not a concern - stick with the base ISO setting for your specific camera. If you need a fast shutter speed to freeze motion, or if light level is so low that the base ISO requires a very long exposure (30 seconds or more), consider a higher setting.
Guy
Either way, you will get your best image if you can use the actual base ISO. This will give you the best signal-to-noise ratio, which will also give you the best sharpness.
If you're really concerned about noise, you should also look into Exposing To The Right (ETTR) This means that you expose the image so that the highlights are just short of being blown out, even if this means you're overexposing the image. Then you adjust the exposure back to what it should be when processing your file. In this way, you've gotten the most light possible on the sensor, which will greatly enhance you signal-to-noise ratio and give you the cleanest image.
Of course, if your scene has a big dynamic range already, that might not be of too much use. But it very good practice with digital where you can do it.
Just to be clear, this multiplication is a change in the amplification at the pixel or read-out level. (I'd say it uses the same data from the pixels, not from the sensor.) It's not quite the same as capturing an image and then multiplying the values after the fact.
Guy
Guy
That is pretty much what I have always done....
Dang, that was quick and unbelieveably thorough...
Thanks y'all....
I guess I should have mentioned my main camera is a Nikon D300s with a D200 as a backup...
200 is the last number on the readout but it has 3 more lower settings down to 100..
Thanks again for all the information...
Tom H
For example, our own testing and use has shown that the Nikon D300 turns out better results at ISO 2400 and even 3200 than the D2X can manage at ISO800. A "generation" step in technology from older to newer models certainly made an improvement between those two, even though the 300's cost roughly 1/4 the price of a D2X. The first time I shot them side-by-side was on a commercial aerial shoot early in the morning when I carried the D300 as high speed "backup" to the D2X, and turned out virtually 100% good results from the 300 at ISO2400 and ISO3200 and not a single usable image from the D2X at ISO 800. The client has since used some of the D300 images for wall-sized photos in tradeshow booths and advertising, but I would have been hard pressed to turn out a decent 20x30 from the D2X images.
I don't usually shoot a lot of low light stuff. But, I was shooting a night high school football game with the D300s and the D200... with the ISO run way up....the images from the D200 were extrenly noisy and poor, the D300s' were great...whatever Nikon did was a heck of an improvement...
No kidding!
I've posted this before, but here's a cull from that shoot. It was around 5:30AM, heavy overcast and rain, and I had to shoot in very tight turns at 80 knots through a small triangular window at the "copilot's" seat. It was a very narrow shooting alley between the prop, window frame, wing and float, and I had to be really quick. The framing in this shot went all haywire on me when we hit a sudden downdraft, but there is no noise in those blacks. The D2X shots looked like I was shooting in a snowstorm at 3200 ISO (Hi2), while at 800ISO shutter speeds went waaaaaay too low for the circumstances.
Good point, Guy. I don't want to confuse the issue further...