Common DSLR Myths - Always Use The Lowest ISO
In the first of our Mythbusting series we are going to look at a common myth that you should always use the lowest ISO number possible to get the best results This is based on the knowledge that the higher the ISO number you use, the more noise (digital artifacts) will be created in your image While this is certainly true, what we are going to examine in this article is wether or not you should always shoot in the lowest ISO number your camera can handle in order to get the best images Will this myth be confirmed or busted? Continue reading to find out
Understanding ISO
The different ISO settings will control the light sensitivity of the camera, the problem is that the higher you crank the ISO setting, you will introduce more noise effects In a dim room with no other lighting available, you can increase your ISO setting in order to make the camera more sensitive to light New cameras actually perform quite well at ISO 1600 which was unheard of only a few years ago Upcoming cameras will be able to shoot very usable images at ISO 6400. If we don’t want to add any unneeded noise or digital artifacts if possible if we want the cleanest images we can possible get
Myth Expectations
According to the myth, if our camera will go down to ISO 100, then so long as we can have the aperture that we want to use and a fast enough shutter speed, then we should shoot at ISO 100 whenever possible. To test this we will take a series of images of the same scene at different ISO resolutions and compare the results. If this myth is true, than our images at the lowest resolution will be the ones to keep.
The caveat here is every camera does behave differently and the results may vary slightly between different makes and models, but the overall result should apply to pretty much any camera.
Testing the myth
We setup a shot in mid-day that could easily be handheld since the shutter speed will be plenty fast enough. By zooming in we can see the differences between the different images.
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At these resolutions the differences between these images is very subtle and you really need to look closely at the leaf you will see some color noise. While this at first appears to be the only real difference, we should be able to see even more when we zoom in even closer.
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Now you can see the noise that is present in the ISO 1600 image a little better but you can also see an odd effect in the ISO 100 image, note that the ISO 100 image is not as sharp at the ISO 400 image.
This is actually a phenomenom we noticed when shooting a lot of wedding photos. While we always believed that shooting at the lowest ISO setting would give us the best image, it actually was a sacrifice between noise and sharpness. The higher the ISO image the more noise you get, but the lower the ISO setting the less sharp the pictures were. The sweet spot for different cameras may vary but with many other settings, you will not get the best results from either of the two extremes. With our Olympus E-500, the sweet spot for ISO was between 200-400 ISO and with our Canon cameras the sweet spot is between 400-800.
Results
While it may sound intuitive that the lower the ISO the better the image but the results do speak for themselves and show that this is not actually true, the best shots will result in a setting that is not at the extreme of the available ISO levels.
erik said
am December 2 2007 @ 4:28 pm
I’ve recently been discussing the issue of what ISO to choose with a co-worker - he brought up another good point that can could be another arrow in the quiver for your argument that you shouldn’t always shoot at the lowest ISO your camera is capable of.
He brought up the point that many beginner and/or inexperienced DSLR owners (myself included until just recently) will shoot at a low ISO at the expense of having to deal with motion blur in their photos due to the long exposure times made necessary by the low ISO. In nearly all cases, it’s much more acceptable to have a bit of noise in the image than to have motion blur. Noise, to some extent, can be reduced fairly effectively in post-processing, while unintended motion blur renders photos useless.
Geoff R said
am December 3 2007 @ 12:14 pm
Sweet, it’s like myth busters for photography!
Really great article, fun to read and I learned a lot.
ShoShoots said
am December 6 2007 @ 3:05 pm
Great article simple and very informative. I’m doing a weeks worth of articles on my blog TheyShootin.com. Because for beginners
myself included understanding ISO is a major step to taking better pictures.
Thanks Much.
Udi said
am December 9 2007 @ 8:10 pm
Thanks man. I was not aware of this. Wonder if this is true for Nikon as well.
Thanks for sharing your blog with me. I got it in my RSS reader.
- udi
Chuck Norcutt said
am December 20 2007 @ 12:53 pm
Busted? Hardly. I have to say that this is a perfectly inadequate test by someone who seems not to understand what they are doing from a technical perspective.
First, critically examine the text of the article. These test shots are made hand held and at relatively large magnification. The ISO 100 shot is at 1/250 second which is well within the range for problems from camera motion, especially for a small sensor camera at close-up range. Second, carefully observe the position of the leaf in the ISO 800 shot compared to the other three shots. The leaf in the ISO 800 shot has
been pushed up and to the right by an invisible force… called the wind. So we have the camera in motion and the subject waving in the wind and we’re supposed to judge sharpness.
In fact, although noisier, the sharpest photo is actually the ISO 1600
shot. Pay attention not to the leaf but to the bottom of the pot and what looks like a clump of peat moss. At ISO 1600 the 1/4000 sec shutter speed has finally stopped all motion. In fact, I’m not
completely convinced that we’re not also seeing some changes in depth of field, possibly from changes in aperture. The ISO 1600 shot at 1/4000 sec should have been taken at 1/3200 sec if the light had not changed. Why was it taken at 1/4000? What aperture was used and why?
Perhaps what the tester says is true. I don’t know. But you sure can’t make any judgments from this test.
Chuck Norcutt
KerryG said
am December 25 2007 @ 4:53 pm
Thanks for your comment Chuck and I may revisit this one if we get enough comments like yours. While in a perfect lab environment the results may prove to be different but in real-world tests where you have things like wind, motion, breathing, etc to deal with, shooting at a low ISO means a slower shutter speed and thus more bluring.