Odd Live View

The normal behaviour of live view with my K3 is that the brightness of the image on the rear screen depends on the exposure value - increase the aperture or exposure time and the screen gets brighter and vice versa. However, with the Laowa 25mm macro, that does not happen. Brightness varies with aperture (which is set on the lens, not the camera) but does not vary with exposure time. The lens is, of course, fully manual with no electronic connections for anything and no aperture lever. It seems reasonable that brightness varies with aperture because changing the aperture on the lens directly changes the amount of light reaching the sensor. But the exposure time has nothing to do with the lens and the camera has all the information it needs to vary brightness with exposure time - it just doesn't do it.

So my question is whether this behaviour is found with other lenses which have limited of no communication between lens and camera (I can't check because I don't have any others). Or is live view behaviour with the Laowa just weird? Or is there an obvious reason and my brain is rotting with age ??

Steve

I think the + - EV results with an AF lens or an 'A' setting lens are electronic interpretations of what the sensor is seeing. Remember that the iris remains wide open until the shutter release is pressed so whatever you do with the EV button won't physically affect anything at all up to that point. Not so with a manual, non 'A' setting lens when twiddling with the aperture ring will have an instant, direct effect on light reaching the sensor. In either case, the change in EV isn't made by changing the exposure time but by an electronic change to what is recorded. (I think) (or do I?).

Agree with what you say about electronic interpretation of what the sensor is seeing and the difference between 'A' and non-'A' lenses. And while I don't have a manual, non-'A' setting lens, it dawned on me that I do have an adapter for reverse mounting a lens on the camera, which eliminates all elecrical and mechanical communications between lens and camera. So I reverse mounted a lens with an aperture ring and get the same behaviour as with the Laowa. It is at least consistent!

But it's still puzzling because the in-camera electronics is definitely doing something to decide how bright to set the live view image. In fact, I can catch it thinking - quickly change the aperture on the Laowa or the reverse-mounted lens and the image brightness changes gradually, not suddenly. Sometimes it even overshoots before settling down to what the the electronics decides is the 'right' brightness. So since it is obviously doing some calculating to get the brightness to vary with the intensity of light reaching the sensor (which is what varies when aperture is changed), the question remains: why doesn't (or can't) it do some calculating to vary brightness with exposure time? Is it a fundamental impossibility which my brain hasn't thought of or just something that the software developers didn't think of putting in the software?

Interestingly, RobL started a thread 'Using flash in live view' back in Feb 2020 in which he wondered whether there was a way of making live view remain bright while deliberately underexposing for natural light. The only way to get it was a work-round (aka a fudge). Perhaps live view needs to be more configurable ...

Steve

I think its main 'aim' is to present you with an image that you can see clearly. It isn't much use showing you the 'truth' if that truth is so dark you can hardly see it. The calculations it is performing to maintain that must be immense.