"De-couple" ISO from exposure time?

[dno]

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I've been experimenting with long exposures for moonlight landscape photography with the Q2. I'm frustrated by the camera not allowing me to set exposure time above a limit it imposes based on ISO setting. For example. if I'm set at ISO 800, it will not allow anything beyond a 15 second exposure, which in my case is not enough to get the results I want. After 15 seconds, what is available is T, which seems to result in a 15 second exposure. I'm loathe to add noise by increasing ISO beyond 800. Full moon in two days...suggestions?

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[marchyman]

Increasing ISO won't help.  ISO 1600 gives you an 8 second max, 3200 a 4 second max.  That's for the Q.  This video says it's the same for the Q2: 

And T mode doesn't help.  It has the same limits.

[Jared]

I assume these are tripod mounted shots, yes? One solution—and a very good one—is to take multiple 15s exposures and then merge them together using the photo editing software of your choice. This is the technique used almost universally by astrophotographers. Works a treat. You can get all the cloud blurring you like, all the signal you want, and still shoot at base ISO.  Generally, I would recommend pushing the ISO to 1600 on the Q even though your exposure time will shorten, then just take lots and lots of pics. Median combine will help reduce hot pixels and get you good SNR. Read noise is lower at ISO 1600 than at base.

[dno]

Well, the point is that the way the Q2 is set up, it limits my control, for reasons I can't understand. On any other camera I've had, I have the freedom to experiment with ISO settings, aperture, and time to suit what I'm trying to accomplish with the shot. The Q2 acts like it knows better. I could understand it doing this in a fully or even partially auto mode, but when I'm controlling everything manually I would rather not have the camera make decisions about ISO for me.

[Jared]

Yes, Leica has a long history of the engineers deciding they “know better” and not letting you choose settings that they feel might not meet Leica standards for quality. For example, many Leica’s won’t let you turn off long exposure noise reduction. Some will automatically stop down if you choose a focus distance that is not optimal for the lens, e.g., go to f/2.8 rather than wide open if you focus close. Note, this is not the bellows effect, the camera actually closes the diaphragm for better image quality.  Too bad if you wanted it wide open. And, as you have already found, Leica doesn’t want you to take a long exposure if the result might be hot pixels from thermal noise, so they set maximum shutter speeds by ISO.

The workaround I posted is the only one I am aware of, and it is very effective. Yes, it would be nice if Leica didn’t impose these limits, but they do, so... Give it a shot.

[dno]

Thanks, @Jared, I will.