Is It Time to Abandon the ISO Scale?
by Peter Zack
I pose this question for a couple of reasons: The ISO scale is 1) misleading and 2) misunderstood. I would be surprised if manufacturers pushed to adopt a new scale though. More is better, right? If brand X can shoot at ISO 6400 and Brand Y can shoot at ISO 12,800, then Brand Y must be, like, 6400 times better or something. Right? Nope it’s only 1 stop. The ISO scale was developed in the film days and as far as I’m aware, the fastest film available (other than maybe some specialized scientific films) was Kodak T Max at 3200. Digital sensors have far exceeded that today.
While not exactly on point, I think the cartoon sums up part of what I feel is a misleading issue. The cartoon does make light of the technical understanding of ISO. Have you ever read the WiKi article on that subject? Even my eyes glaze over. I am willing to bet that a lot of shooters (I’m guilty of this) have set the camera at ISO 4000, thinking they gained a lot of sensitivity but not as much noise as 6400 gives them. Well not really. That’s only 1/3 of a stop and they really gained very little in shutter speed, just lost some detail and increased the noise a bit. The 1/3 boost in shutter speed certainly isn’t going to make much difference in freezing the action in low light. Other choices, a tripod, faster aperture, adding a flash or more light etc, shot at a lower ISO, would create much better photos in many situations.
From here on I’ll drop the ISO part, assuming you know what I’m talking about.
The scale makes no sense with today’s sensors and the ones coming in the future. We already have cameras that can shoot above 100,000. Who knows where they will be 2,3, 4+ years from now. Shooters at all levels of experience may not understand the sensitivity steps, make the wrong choice in a hurry, or get a little hoodwinked at how much extra latitude you get from 6400 to 12,800 because the number sounds so much bigger than it really is. Think in terms of salary: If you make $51,200 a year and the boss offers you a new job at $102,400, that’s a huge leap. Your entire life just changed. Well that’s how we think; we don’t see that it’s just one stop faster.
Is one full stop a big deal? Sure it is, shooters go nuts to buy a lens that is 1 stop faster. Also, the scale is exponential. So 200 is twice as sensitive as 100 and 400 is 4 times as sensitive as 100. In terms of what you can do with that 1 stop, It means you could shoot at 1/60th at 1600 and 1/125th at 3200 and get the same exposure results. That could be the difference between stopping the action and not while taking family photos indoors. In my thinking though, if the scale was more straightforward, people would understand better what they gained when going from 3200 to 6400. Sometimes, that one stop and added noise might not be worth the trade-off for a faster shutter speed.
I’d suggest a new scale that really reflects the steps and gain as you turn up the dial. Plus the smaller numbers would be much easier to display in the viewfinder. This way, you can better understand the advantage and relationship with the other 2 parameters, shutter speed and aperture. This would really benefit new buyers, people who have never shot film or who moved from a point and shoot to a DSLR for the first time and never really considered ISO before.
My hope is that some day, sensors will natively go below 100. I really miss how incredible Kodachrome 25 was. So I suggest the scale start at 1 which would equal 100 now and consider the possibility of even lower sensitivities. Then if we get ISO’s below 1 (100) the scale would show a negative. Further, the scale would need to be similar to the aperture scale. for half and 1/3 settings.
Maybe something like this, reflecting 1/3 and 1/2 adjustments:
ISO 12, 25, 50, 64, 80, 100 = -2, -1, 0, 0.3, 0.7, 1.0
ISO 100-200 = 1.0, 1.3, 1.5, 1.7, 2.0
ISO 200-400 = 2.0, 2.3, 2.5, 2.7, 3.0
ISO 400-800 = 3.0, 3.3, 3.5, 3.7, 4.0
ISO 800-1600 = 4.0, 4.3, 4.5, 4.7, 5.0
So then your basic scale is 1, 2, 3, 4, 5 etc. If 100 = 1, then 102,400 would equal 10. We’ll call it the EtL scale. Simple and straightforward. Fractional steps would directly correspond to 1/2 or 1/3 step adjustments to your shutter speeds. I think a much less confusing and more logical way to display your shooting information in the viewfinder. You instantly realize that you’ve only gained a stop and may be better to open the lens up a stop, or decrease the shutter speed when you can, to get a cleaner image.
Cheers and good shooting. –Peter Zack
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Tags: Cameras, DSLR, High ISO's, ISO, ISO 102800, ISO Scale, Nikon D3s