MF Clarification

Started Jul 4, 2011 | Discussions thread
rrfischer Regular Member • Posts: 232
Re: S and M are slightly different - S lets you set Auto ISO

TiagoReil wrote:

In Auto ISo you (the camera actually) cant go past 1600. That is a limitation in the firmware. So you basically have only 4 steps that the camera can choose. 200, 400, 800 and 1600. Remember that each step you set in the shutter speed up, is one the camera must set up in ISO, so basically, you can't move much. So basically you are almost in manual, because you have to match Aperture an Shutter to that limiting amount of ISO the camera is setting. You can check it taking one pic when it starts to blink going to the dark. Check all the photos, they will always be at 1600. It can´t go higher.

I know that it takes thirds steps with ISO (i think it is not actually thirds, but yes, it takes halfs or thirds that you cant set manually) but that you can control also with the shutter, you have thirds. But the problem is the range. You have a very limited range of light (only 4 steps) and you have to be careful with it. In a way you are doing almost Manual but instead of having an exact exposure zero, you have a range in wish to get exposure zero.

I dont mean to criticize you, if you actually find it helpful. Also, if you use manual, please put how it felt, if so much different or similar. Personally I use aperture priority always and always check the ISO I set manually and the speed before taking a shot (to avoid blurring), and compensate if needed.

Just to add a bit more to the discussion:

Both A and S+AutoISO are prone to overexposure and underexposure. As you mentioned, the range in S+AutoISO is only 4 steps. In A, supposing a common 50mm with aperture from 1.4 to 16, it's about 8 steps. That's a much better versatility, but it doesn't help when light doesn't allow you to abuse all that range. If you can only have half of it (1.4 to 5.6, for example), then it's as much versatility as in S+AutoISO.

There are situations in which S+AutoISO is actually more versatile than A+AutoISO, since in A you simply can't fix the most important value of the equation, without which you won't get even a single sharp photo. Also, underexposure in not much of a problem if you can still get a good histogram that can be adjusted in post processing. Camera shake, however, can't be fixed like that.

I'm forced to use S+AutoISO every now and then. It happened with me a few days ago in a bright (not the brightest) day, but the subject was in the shade. In A, I'd get too slow shutter speeds, so I'd have to keep adjusting both exposure compensation and ISO (with A+AutoISO, I don't even know how the camera will figure out I need a high shutter and high ISO, instead of a lower shutter and lower ISO). So, switching to S+AutoISO, I set the minimum shutter speed to 1/320 or even faster (shaky hands) and adjust the aperture according to what the screen gives me. Since my 200mm is bad at 4.5, I prefer to step it down once to 5.6 or twice to 8. In S+AutoISO, the clue of underexposure is much more evident, as a darker screen and a blinking number, compared to a low X number in the 1/X value. That hints me much better that I should open the aperture. Overexposure should never happen with something narrower than 4.5.

All in all, the concept of S is gone when you attach a manual lens, since aperture will never be automatic. However, the limit of not allowing AutoISO in M is nonsense, so that's a workaround that's been very useful to me.

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