Why are some compact cameras zoom in a bit after zooming out? - Page 1
Forum section: electronics / general

author: tevam46806
author_rank: Newbie
timestamp: December 13, 2019, 02:42:59 pm
content: I don't know if anyone here ever notice this on a point and shoot camera with optical zoom: If you zoom in, it's normal; but when you zoom out, immediately after the operation, it will go back a little bit...It only happens on some models, and it's quite common years earlier, on affoardable compact cameras.I even saw a automatic film camera(I mean the one using film instead of image sensor, not video camera) also do that. I want to know the reason. Thank you!

author: jmsc_02
author_rank: Regular Contributor
timestamp: December 13, 2019, 03:31:37 pm
content: Maybe to compensate mechanical hysteresis?

author: tooki
author_rank: Super Contributor
timestamp: December 13, 2019, 03:39:49 pm
content: You mean why on some lenses, the lens barrel reaches maximum extensionbeforereaching the maximum focal length? You’d have to study the lens formula of the lens: how the various lens elements move around as you zoom and/or focus. I’m not an optical engineer by any means, but I assume that in such lenses, zooming actually moves many groups of elements, and that the maximum movement of every group involved would have some deleterious effect, so they bring some of them back instead.P.S. It’s not just compact cameras, it’s not uncommon in zoom lenses for interchangeable-lens cameras (like SLRs and mirrorless), too.

author: tooki
author_rank: Super Contributor
timestamp: December 13, 2019, 03:42:09 pm
content: Quote from: jmsc_02 on December 13, 2019, 03:31:37 pmNo, the OP is talking about significant movement, not just compensation for slop. On one lens I own, I think that it retracts about 20% once you move it the last 10% of the zoom range. (Disclaimer: I don’t have it in front of me, and I haven’t used it in ages, so I could be way off in the numbers.)

author: tevam46806
author_rank: Newbie
timestamp: December 13, 2019, 04:09:12 pm
content: Thank you everyone, but no one understand my question yet...It only happen on some motorized optical zoom compact cameras.When user give a zooming out operation, immediately after every zoom out action(user release the button, or reach lens limit), the motor intentionally drive in reverse direction(zoom in) a little bit. No matter what position the zooming begin, or end, or duration.This deos not happen to the zoom in command itself.Hope this is clear...

author: wilfred
author_rank: Super Contributor
timestamp: December 14, 2019, 12:33:59 am
content: Maybe the cheaper compact cameras have lens cams that perform better on the retraction and this movement is used to better adjust the final zoom position. Or the smaller compact camera lenses are made with different design criteria for light weight and retraction into the body of the camera and this dictates a different style of movement to set the lens into final position.

author: Halcyon
author_rank: Unknown
timestamp: December 14, 2019, 12:42:47 am
content: I have noticed this behavior on my Canon point and shoot camera. No idea why it does it, but it doesn't appear to be a fault or poor design. It obviously has something to do with the final focus/focal length.

author: SparkyFX
author_rank: Frequent Contributor
timestamp: December 14, 2019, 01:06:15 am
content: Possible reasons:- Autofocus kicked in and actually focuses something- the lens should not be kept at end stop or it might freeze there if stored in this position- backlash compensation/end stop- switch bounces

author: andy3055
author_rank: Super Contributor
timestamp: December 14, 2019, 01:59:33 am
content: I think it is due to the feedback and the compensation. To focus properly, the feedback loop must send a signal to the focusing mechanism and this goes on till the system has the strongest signal that confirms the best point of focus.The cheaper cams will do this too slow and it takes time which is noticeable. The faster the reaction time, the lesser you notice it and that means higher price.

author: Brumby
author_rank: Unknown
timestamp: December 14, 2019, 07:26:24 am
content: I have no informed opinion, but these are the two thoughts that crossed my mind...Quote from: SparkyFX on December 14, 2019, 01:06:15 am