An earlier, 2011 article on Auto ISO for Canon d-slr users is here:
An In-depth Discussion of M + Auto-ISO for Canon SLRs: Digital Photography Review
A later, October 2013 min-update mentioned a few comments regarding the use of AUTO ISO in
Aperture-priority mode:
How to Use Av + Auto-ISO: Digital Photography Review
"Nikon is several steps ahead of Canon when it comes to Auto-ISO. You set a fixed MSSS (minimum safe shutter speed), or you can choose between five different rules. Under the slowest rule, the MSSS is 1/ (0.25 x FL); under the fastest rule, the MSSS is 1 / (4 x FL), with the three rules in between: 1 / (0.5 x FL), 1 / FL, and 1/ (2 x FL). So the photographer can choose the rule that suits his hand steadiness the best. Even more impressive is the fact that some Nikon DSLRs have User Mode which you can assign a different rule. For example on my D600, I have made U1 mode Av + Auto-ISO with MSSS being 1/ (2 x FL). Whenever I need someone else to take a picture for me, I set the camera to this mode, set the aperture, and I know that their untrained hand is not going to ruin the shot with shake blurs regardless which Focal Length they choose to use on my 24-85mm VR. On the other hand when I use Av mode myself, I stick to 1/FL."
There seems to be a misunderstanding that AUTO ISO use somehow automatically leads to "
High ISO". That is in fact, not necessarily true, whatsoever. Besides, what is "High ISO? 400? 500? 640? 800? 1600? 3200? It depends on the camera's sensor, and the lighting conditions, and the intended use of the image. The user sets the A)preferred ISO, as well as B)the ISO ceiling. The camera will use the preferred ISO value, and will only increase ISO up to the ceiling ISO, which is determined by the user, and the user's understanding of the situation and priorities. Ergo, AUTO ISO does not directly lead to "high ISO" values being used; the USER still has control, but no longer needs to constantly risk interrupted shooting and yo-yo'ing the settings to avoid compromising a fixed manual shutter speed and a specific f/stop preference when his ISO value is not high enough. Indoors under artificial, narrow-spectrum light at arenas and stadiums, HIGH ISO can look poor, but under full-spectrum daylight, higher ISO can look fine, especially in areas where there's a lot of fill light and limited shadows, like...over or near water. Like--
at the beach.
One of THE biggest uses for AUTO ISO I think is when using slowish lenses like the 70-300 VR-G at places like the beach. Or, when using a camera aboard a boat in activities like saltwater salmon fishing, where the ISO levels are LOW on one side of the boat, but the brightness dropoff on the "shadow side" of the boat, looking down into green water, is simply HUGE. The conditions there demand a FAST shutter speed, to freeze movement from wind and waves, but you're pretty much desirous of a small f/stop to get depth of field over a wide distance range, and especially aboard the boat. Other people mentioned birds in flight; now that we're gonna see the new Tamron 200-600mm f/5~6.3 become the new, popular birder's lens, we're gonna see more and more people using AUTO ISO because they are "stuck" in a very, very narrow range of usable f/stops. AUTO ISO in Manual is a feature that has become more useful as variable maximum aperture tele-zoom lenses kind of "crimp our style".
I shot a beach portrait session a few weeks back with some AUTO ISO, and the 80-200 2.8 AFS and 200 VR-G as my only two lenses. I went for Low 1.0 (E.I. 50) to Low 0.7 (EI 64) to a maximum of 400 ISO. Worked GREAT, and the issue was mostly wind of 20-25 MPH, all danged day long, necessitating fast speeds, as well as f/5.6 or f/6.3 for desired depth of field, no matter where the subject was, in relation to the sun and ocean. f/5.6 at 1/1000 second at ISO 400 was my ending exposure around 6:00 PM.
I was able to keep the NEEDED speed and f/stop pairing constant in front-lighted, side-lighted, and backlighted conditions without even a second thought to ISO as I directed my subject how to pose and move, even with the low ocean sun causing huge brightness level fluctuations. And there's really no need to worry about ISO levels when working by the seashore on light sand...there's just not a lot of penalty at 400 ISO on FX Nikon as opposed to 100. As always, the key is understanding what the most-critical parameters are. And the goal is to get the best "pictures"...not to come home with the highest pure, technical image quality by always slavishly using baseline ISO. The pictures are much more-important to me than some idea that only the bottom two ISO values are any good.
This is actually a fairly new way to shoot photos. This is a HUGE advantage if you understand when it's a huge advantage. I've had scenarios over the last five years where, near the ocean, the LACK of AUTO ISO has ruined shots, and had entire days where the sun played peek-a-boo all day long, as it does here in most of late winter and springtime. AUTO ISO in Manual mode is a Godsend, now that I know how to use it, and have actually given it a fair shake.
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