RX100 CIZ - change to focus/exposure area

[dalemccl]

When you zoom the RX100 into Clear Image Zoom range, it changes the on-screen auto-focus area indicator to a large area bounded by dotted lines, regardless of which auto-focus area is selected in the menu. Two questions about this:

1. In CIZ zoom range, what area of the scene is the RX100 using to determine where to focus?

2. Does the camera also change the auto-Exposure area to the area inside the dotted lines, or does it still use the exposure area you selected in the menu?

 

[elliottnewcomb]

good question. hope we get an answer.

 

[Robert Deutsch]

I don't know about No.1, but No.2 is easy to answer. I pointed the camera at a scene where there was a lit table lamp at the center, zoomed to 3.6. The shutter speed on auto was 1/13. When I zoomed in to 7.2, the shutter speed changed to 1/30. Conclusion: in CIZ, the exposure is based on the zoomed-in image.

Bob

When you zoom the RX100 into Clear Image Zoom range, it changes the on-screen auto-focus area indicator to a large area bounded by dotted lines, regardless of which auto-focus area is selected in the menu. Two questions about this:

1. In CIZ zoom range, what area of the scene is the RX100 using to determine where to focus?

2. Does the camera also change the auto-Exposure area to the area inside the dotted lines, or does it still use the exposure area you selected in the menu?

 

[dalemccl]

I don't know about No.1, but No.2 is easy to answer. I pointed the camera at a scene where there was a lit table lamp at the center, zoomed to 3.6. The shutter speed on auto was 1/13. When I zoomed in to 7.2, the shutter speed changed to 1/30. Conclusion: in CIZ, the exposure is based on the zoomed-in image.

Bob

Bob,thanks for the reply and for doing the experiment. I was actually wondering which "portion" of the zoomed-in image it uses for exposure: the entire area within the dotted lines, or only the exposure area selected in the menu. In your experiment, when you zoomed to 7.2x, I assume the overall brightness of the frame increased since more of the lamp was filling the frame than at 3.6x zoom. Thus the faster shutter speed when zoomed to 7.2x than when zoomed to 3.6x. But was that because it used the exposure area that you had set in the menu, or because it used the entire area within the dotted lines? Hard to tell - either way would lead to a lower exposure at the higher zoom level. Do you agree, or is my logic faulty?

I used your lamp idea to experiment. I set the exposure area to "Center" in the menu, then zoomed into CIZ territory, composed with the lamp in the center of the frame, depressed the shutter half-way and noted the exposure info. Then repeated this with the lamp at the edge of the dotted line area, (still fully within it - just not in the center). Then repeated again with the lamp just outside the dotted lines.

It was clear that with the lamp in the center, it was using a lower exposure (lower ISO in this case) than with the lamp at the edge of the dotted area, or outside the dotted area. That could have been because it was using the center area for exposure (per my menu selection), and the lamp in the center was bright. Or it could have been disregarding my menu setting and using the entire area between the dotted lines, but that entire area was brighter when the lamp was in the center than when it was at the edge of the dotted lines, or outside the dotted lines.

So I was unable to draw any conclusions. At the moment, I can't think of a better way to test this, so it remains a mystery to me. I'd be interested in any suggestions you (or anyone else) can offer on how to properly test this.

 

[rmwpg]

I don't know about No.1, but No.2 is easy to answer. I pointed the camera at a scene where there was a lit table lamp at the center, zoomed to 3.6. The shutter speed on auto was 1/13. When I zoomed in to 7.2, the shutter speed changed to 1/30. Conclusion: in CIZ, the exposure is based on the zoomed-in image.

Maybe, but what happens to the aperture when you change the focal length?

 

[Robert Deutsch]

I don't know about No.1, but No.2 is easy to answer. I pointed the camera at a scene where there was a lit table lamp at the center, zoomed to 3.6. The shutter speed on auto was 1/13. When I zoomed in to 7.2, the shutter speed changed to 1/30. Conclusion: in CIZ, the exposure is based on the zoomed-in image.

Maybe, but what happens to the aperture when you change the focal length?

Nothing. It stayed at f/4.9. But that's because it was in the Aperture mode, set at the widest available aperture.

Bob