(bolded) Roger's issue is something different.
Originally Posted by fotografz
Regards the "full-time 'Setting Effect On'", this is indeed the default but Leica implements preview modes differently compared to Sony. For the SL:
- (FN button) short press :: Normal | Aperture Simulation | Exposure Simulation
Pressing the FN button engages three different preview modes in rotation. These operate somewhat differently depending on whether you are using a dedicated SL or T mount lens vs an adapted M, R, or other lens.
Normal mode is designed to keep the viewfinder consistently bright for focusing and framing in normal use. The brightness level is somewhat variable dependent upon both ambient illumination and evaluated exposure. (This is Roger's issue: He finds the viewfinder too dim and contrasty in normal circumstances under bright, contrasty lighting. I don't find this to be the case, the source of our disagreement. The SL offers no adjustment of the EVF baseline brightness at the present time; it does offer adjustment of the LCD baseline brightness—automatic, then from high to low in five steps.)
Aperture Simulation (aka DoF Preview) mode allows you to evaluate exposure and focus zone by forcing the lens to stop down to taking aperture when it is enabled. This is a 'press-on, release when exposure or another mode is selected' operation. With adapted lenses, it has no effect since the camera*body is not in control of the aperture setting, and the exposure system continues to adapt to changing light situations. With the SL lens, it locks the exposure setting and stops down the lens so that you can see how that setting affects the scene as you move around the scene with the lens. The behavior may be influenced by exposure time following the Auto ISO range setting or minimum exposure time setting, and that may differ between the SL lens and adapted lenses.
Exposure Simulation mode is also a 'press-on, release when exposure or another mode is selected' but it goes a step further than the Aperture simulation. Exposure simulation takes full account of the exposure time that the metering system evaluated as well as stopping down the aperture. With the SL lens, the exposure is locked and the simulation shows what the exposure will evaluate to with full exposure time elapsed. With an adapted lens, the exposure continues to float dynamically. "What the exposure will evaluate to with full exposure time elapsed" means that for long exposures, if you have the histogram view active, you can see the camera accumulating the exposure in steps; for example, if the camera is in Manual exposure mode and the exposure set is three seconds in duration, you will see the histogram and display brightness step a couple of times until three seconds have elapsed and then the exposure will stabilize and the histogram accurately reflects the true exposure. (I have found exposure simulation mode to be invaluable when setting exposure for use with macro tubes or bellows with lots of extension and long exposure times.)
- (Camera Menu) Exposure Preview ON|OFF
The exposure preview feature works when the shutter release is half-pressed. The default is "ON". What this does is a similar to exposure simulation on the FN button but the behavior differs depending upon whether you are using AutoISO or a fixed ISO setting. With AutoISO, the maximum exposure time setting in the AutoISO Settings is enforced and the half press will adjust the viewfinder to reflect the exposure that will be made. It is particularly useful to set "OFF" when working with manual exposure and flash units. For example, if you've set ISO 200 and 1/125 sec for use with your studio flash at f/11, when you half-press the shutter release with Exposure Preview set ON the viewfinder will dim to almost black in many circumstances, making it difficult to see the subject at the moment of exposure. Turning Exposure Preview OFF allows the brightness of the viewfinder to be preserved for focusing, framing, and seeing the moment of exposure clearly.
Sony's implementation of Display Preview is much simpler: in the A7 (IIRC) it implements its notion of exposure simulation all the time, allowing the EVF/LCD to be essentially a visual exposure meter. It doesn't do the full exposure simulation the way the SL does—there is a limit to how much light the display refresh will accumulate to track actual exposure. I don't recall that it would track (or stay bright) even with proper exposure settings past some large fraction of a second (say 1/10 or 1/5) but I no longer have the A7 body to experiment with to ascertain the limits. It's behavior with flash is the same as the SL, which is why they give an option to disable it. It works nicely in the exposure time range that Doug uses (I doubt Doug is shooting birds with a 500mm lens at multiple second exposure times ... :-) but doesn't work particularly well in the circumstance where the SL's exposure simulation works well for me (macro capture of small negatives with bellows and 2.8:1 magnification ...).
There are many times with all these automation systems that I throw up my hands: I turn the camera to manual exposure, disable all preview modes, and just use a hand held meter. It's just too much trouble to figure out the right combination of automation and preview settings, and I know what I'm going to get with an exposure meter and manual settings. Never mind the fact that I can make an exposure and see the result a second later, adjust and reshoot if I'm working with more static subjects.