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Nx1 16-50 2-2.8 exposure change while zooming.


JS
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Hi,

Is the exposure change while zooming using 16-50 2-2.8 lens in the above video normal behaviour for a variable aperture lens? Or do I have a faulty unit? I've tried every auto/dynamic/framing/metering etc. setting and nothing seems to get rid of it. Both camera and the lens are equipped with the latest firmware. Other people have wrote about it also in the b&h reviews(http://www.bhphotovideo.com/c/product/1022903-REG/samsung_16_50mm_f_2_2_8_s_ed.html).

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Looks normal to me. It goes from f/2 wide open to f/2.8 zoomed in and the other way around. It has to meter and adjust exposure with steps of shutterspeed/ISO accordingly if you run things automatically, that's not a fluid process. I think you're asking too much if you expect this to come out nicely...

-- ok, with the later addition of the aputure set at f/3.5, that is interesting. I think we've seen exposure breathing like this before on the NX1, no?

--- hum, check: http://www.eoshd.com/comments/topic/7770-nx1-exposure-drift-problem-fix/ perhaps.

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Thanks for the replies. Forgot to mention that it was shot f3.5, 1/50, iso was 800 or 1600. And I'm not sure if the aperture actually changes after it's settled. I think it stays the same. This doesn't happen while panning from bright to dark(the old exposure drift problem). Only while zooming. 

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Thanks Don, so maybe this a feature with this combo? Are there any nx1 users who could confirm this? And maybe someone with a different zoom could test if they are able to get a "clean" zoom? 

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5 hours ago, JS said:

Thanks Don, so maybe this a feature with this combo? Are there any nx1 users who could confirm this? And maybe someone with a different zoom could test if they are able to get a "clean" zoom? 

I have same issue with 16-50 PZ. Even if I have full manual mode and aperture eg. f8 then I can see changes in exposure... it seems to be firmware bug to me.

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I'm fairly sure that the reason is that your angle of view will change slightly as the lens focuses. This is not unique to the NX1 and is a lens design property. The change in apparent exposure is a consequence of this.

If you watch the video you will notice that the exposure changes happen when the lens is refocussing. If you control the rate of autofocus adjustment you can probably minimize the exposure effect you are observing.

If you have the camera in continuous focus mode and aim it at a scene where everything is in focus due to depth of field, but the autofocus system is making fine adjustments based on the elements within the image, you will sometimes see what looks like small changes in the angle of view constantly happening.

One more thing, remember that as you zoom out from 50mm to 16mm, the lens will be collecting a lot more light. If you have aperture, shutter speed and gain all fixed, this will result in increased exposure. I am assuming that that you have aperture and shutter speed fixed, with gain floating. What happens when you quickly change your zoom ratio as in the video, changes to the gain will not happen until metering is done. Metering is probably happening at the same rate as refocusing, so until the lens starts to refocus it will still have the old gain (and hence inconsistent exposure). This would also apply to manual zoom lenses, since metering is not instantaneous.

I guess what you need to do is just zoom more slowly, and the problem will go away. Essentially it is a property of the angle of view and the speed at which metering takes place.

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