intelligent Iso and ZS19

Started 9 months ago | Discussions thread
Ianperegian
Senior MemberPosts: 2,447
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Re: Exposure
In reply to Erik Ohlson, 9 months ago

Hi Erik,

Thanks for doing those tests. I think we'll have you doing some chart tests before long!

In the case of your test A, I assume that the the zoom was at full WA, that is, a FL of 24mm (35mm equiv.)? You quote for "widest aperture A mode": f/3.3, 1/2000s. A shutter speed of 1/2000s is the fastest that is available, therefore with the aperture at f/3.3, the camera was at its extreme limit in terms of the exposure. It could be (without seeing it) that the shot was somewhat overexposed, as I noticed that you said: "all photos look fine, although some differences of exposure are noticeable".

You quote for P mode: f/4, 1/1600s. If the FL was 24mm, then that is not the widest available aperture, which is f/3.3. However, at 24mm FL, the resolution at f/3.3, f/3.5, f/4.0 and f/4.5 are all the same for the ZS19/20, at 2150 LPH. This is the relevant table:

Therefore, at 26mm FL, anywhere between f/3.3 and f/4.5 gives the same resolution. I think we can assume that the Panasonic engineers were well aware of that, and therefore they "tuned" P mode to give the optimum results, but without overexposing the images. That is borne out by your test with P mode which shows f/4 and 1/1600s, which is not at the limit of the exposure range and would not cause overexposure.

If "widest A mode" were somehow always the best setup for the ZS19/20/30, then I think it's reasonable to assume that the Panasonic engineers would provide a mode setting for it.

In the case of your test B, the "widest A mode" settings are not at the limit of exposure, and therefore should not be overexposed, but the other comments I made above for test A still apply.

If you recall, in an earlier thread on this topic I posted my results from actually going through hundreds of P mode shots to see how the aperture was set: http://www.dpreview.com/forums/post/50605286 . That led me to realize that P mode was optimised to give the best resolution while not overexposing.

This is another post on the topic in response to RemyW, who found that he had a lot of overexposed images when he used "widest A mode" on a trip: http://www.dpreview.com/forums/post/51518826 .

BTW I've used P mode in both Hemispheres! I've just recently returned to Oz from France, and I've posted some initial shots from Giverny, all taken in P mode. No overexposure problems and I was very happy with the resolution, which you can examine yourself from the full sized images in my gallery if you wish:http://www.dpreview.com/forums/post/51801920 .

Best regards,

Ian

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