SL2-S and Auto ISO (High ISO)

[bherman01545]

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All;

I was out shooting tonight outside in pretty much darkness (only ornamental tree lights and street lights in the distance) I set the SL2-S Aperture Priority, Auto ISO with a max of 25000, with Floating ISO set to "on".

The Max Shutter Speed was set to Auto. When examining the exif data, I noticed that in pretty much all of the photos, the Auto ISO pegged at 25,000, regardless of whether or not I shot at F/2.8 or F/16. 

It would appear as if the SL2-S chooses to peg the ISO at the max setting (in this case, 25,000) in favor of selecting a higher Shutter Speed - (remember, I'm using Aperture Priority, where I select the Aperture, and the camera selects the corresponding Shutter Speed)

How would I need to set/configure the camera so not to peg the ISO at the max, while still having the flexibility of Auto ISO?

Thanks!

-Brad

[scott kirkpatrick]

What lens were you using and what shutter speeds did the camera give you?  Floating ISO probably isn't relevant here

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[bherman01545]

I was using a Leica 24-90 Vario Elmar. The camera (when set to Auto ISO and Shutter Speed Limit set to Auto gave me shutter speeds as if if was pretty much daylight (dusk or dawn) 1/30-1/90-sec. and the Aperture settings were anywhere from F5.6-F/10.

My thoughts, and after doing research, is that with Auto ISO, the Shutter Speed Limit setting should be set to something like 1/15 or 1/30-sec, (rather than Auto) and the ISO would float down a bit and not be pegged at the max ISO.

The odd thing is when I set the Shutter Speed Limit under the Auto ISO settings to 1/30, in broad daylight, it still floats up to 1/320 to obtain the correct exposure, so it is really not a 'limit'

I sent my query to two Leica Tech Reps the other day, and am awaiting their responses.

Thanks Scott!

Edited January 21, 2021 by bherman01545

[SrMi]

56 minutes ago, bherman01545 said:

I was using a Leica 24-90 Vario Elmar. The camera (when set to Auto ISO and Shutter Speed Limit set to Auto gave me shutter speeds as if if was pretty much daylight (dusk or dawn) 1/30-1/90-sec. and the Aperture settings were anywhere from F5.6-F/10.

My thoughts, and after doing research, is that with Auto ISO, the Shutter Speed Limit setting should be set to something like 1/15 or 1/30-sec, (rather than Auto) and the ISO would float down a bit and not be pegged at the max ISO.

The odd thing is when I set the Shutter Speed Limit under the Auto ISO settings to 1/30, in broad daylight, it still floats up to 1/320 to obtain the correct exposure, so it is really not a 'limit'

I sent my query to two Leica Tech Reps the other day, and am awaiting their responses.

Thanks Scott!

On my SL2-S, with Auto ISO, the ISO stays at the lowest setting (100) as long as the shutter speed is at least the minimum shutter speed specified. ISO will go up only if there is not enough light for the minimum shutter speed at ISO 100. It is OK for shutter speed to go up as long as ISO is at ISO 100.

[bherman01545]

19 hours ago, SrMi said:

On my SL2-S, with Auto ISO, the ISO stays at the lowest setting (100) as long as the shutter speed is at least the minimum shutter speed specified. ISO will go up only if there is not enough light for the minimum shutter speed at ISO 100. It is OK for shutter speed to go up as long as ISO is at ISO 100.

Thanks, that makes a lot of sense. I will look into that

 

[aj55]

To add to SrMi, with shutter speed limit set to auto the minimum shutter speed is approx. 1/(focal length*2) as I found out. In other words, with my 35mm it stays at 1/60th until the iso limit is hit and a slower speed is needed and with my 65mm it stays at 1/125th until a slower speed is needed.

 

Edited February 4, 2022 by aj55

[aspherical]

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I find that the shots I take with auto ISO are pretty noisy.

 

[SrMi]

2 hours ago, aspherical said:

I find that the shots I take with auto ISO are pretty noisy.

If your Auto-ISO images are noisier than when you shoot with manual ISO, then your Auto-ISO settings are not optimal.

Low exposure creates noise, e.g., too small aperture, too fast shutter speed, or too low scene light.

Most likely, your Auto-ISO setting specifies too fast shutter speed.

[Dr. G]

Your other option would be to shoot manual mode with auto ISO, then you can keep an eye on your shutter speed and light metering.  FWIW, when I shoot in low light and need to keep my shutter speed up and ISO lower I'll usually underexpose by 1 to 1 1/3 stops.  There's no issue recovering your files on the SL2-S when you do that.

Edited February 18 by Dr. G

[davidmknoble]

It can also be exposure compensation.  Shooting normal A or S, you still have to consider whether metering a dark or ligh subject and adjust accordingly. 

I just shot the SL2-S in Antarctica using Auto ISO.  Using the 24-90 I set the upper shutter speed to 1/250 sec.  That would then be the max shutter speed.  I still shot with +1 or +1/2 stop in many cases because of the snow.  Sometimes even more.  Then, shooting twilight it might be even or -1/2 stop.

None were ‘noisy’ and I had plenty at ISO 100, ISO 200, ISO 300.

I did the same with the SL2 (which is a noisier sensor anyway) except I used the 90-280 and set upper shutter speed to 1/2000 sec to avoid blurry images at 280mm.

I also limited the ISO for the camera.  I believe I set the SL2 and the SL2-S both to 25000.  The former had high pixel count reducing visible noise and the latter better sensor technology.

When it comes to noise vs. blur, you have to give up the blur and take the noise, unless that is your style.  The rest comes to nailing the exposure and a little noise reduction, but not too much or you lose the detail.

Just my opinions..