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Thread: IS and alt zoom conundrum

  1. #1
    ebrandon
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    IS and alt zoom conundrum

    I love using alt primes, especially C/Y Zeiss and OM on my Olympus EPL-1.

    One of the nicest features is that you can manually set the IS to the appropriate focal length and every lens is image stabilized.

    The problem is that just today a C/Y Zeiss 35-70mm f3.4 zoom arrived, which is supposed to be one of the nicest zoom lenses ever made, and I'm not sure what to do with the IS settings.

    The options are
    1) Turn IS off. Would prefer not to do this, if other options are better

    2) Set IS to 35mm. The logic is that set to 35mm the sensor will move to compensate for camera movement perfectly when the zoom is at 35mm, and in the right direction but not as much as it should at higher focal lengths providing partial IS at higher focal lengths.

    3) Set IS to 52mm. The logic is that this is the "mid point" providing the best average results.

    4) Set IS to 70mm. The logic is that at longer focal lengths you need IS more. The fear is that at shorted focal lengths the sensor will move in response to camera motion more than it should, adding blur to images that would have been sharper if the IS were off.

    What do you think?

    I'm going to go out shooting right now with option 2 and will report back later.

  2. #2
    Senior Member Devon Shaw's Avatar
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    Re: IS and alt zoom conundrum

    I've had this same question when using my Canon FD 35-105mm f/3.5 lens. Will be interested to see what people have to say as well as what your findings are.

  3. #3
    ebrandon
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    Results are in

    Well the pictures are in from the first two hours of shooting with this lens, and my gasted is flabbered.

    All the shooting was done with IS set to 35mm. Without exif data it's difficult to know at which focal length or at what f stop the pictures were taken, but they were at a wide variety of focal lengths and settings, including 70mm which is the most potentially problematic.

    All -- every one -- of the images taken with this lens this afternoon came out tack sharp so I don't know if 35mm is the optimal setting, but it's sure not doing any harm.

    Here are some samples. Smugmug resizes them, but no PS -- straight out-of-camera jpgs.

    http://thebrandons.smugmug.com/Other...3_U3eWP-X2.jpg

    http://thebrandons.smugmug.com/Other...4_r4NPv-X3.jpg

    http://thebrandons.smugmug.com/Other...6_Xg8BN-X3.jpg

    http://thebrandons.smugmug.com/Other...4_ErQ2x-X2.jpg

    http://thebrandons.smugmug.com/Other...7_ykXSz-X2.jpg

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    Re: IS and alt zoom conundrum

    My experience is no where near as disciplined or detailed as yours. However, lately my lens of choice on the E-P2 is the CZ 28/2.8 (and the IBIS is set accordingly).

    The other day, I switched the lens to my Konica 85/18. I spaced and shot over 100 pics. When I realized my error, I thought "S**t, wasted pics."

    After, looking at them, not one sign of blurring, even at speeds of 1/50.

    So....I can see you're not far off the mark.

    R

  5. #5
    Senior Member Annna T's Avatar
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    Re: Results are in

    Quote Originally Posted by ebrandon View Post
    Well the pictures are in from the first two hours of shooting with this lens, and my gasted is flabbered.

    All the shooting was done with IS set to 35mm. (...)

    All -- every one -- of the images taken with this lens this afternoon came out tack sharp so I don't know if 35mm is the optimal , but it's sure not doing any harm.
    IS only plays a role when the speed is too slow for handholding. So if you shot during a sunny afternoon, it is normal that you didn't get any blur problem.

    That said, I don't have a legacy zoom on my E-P1, but I have different focal length (45mm, 50mm and 90mm) and change often between them. When I change lenses, I adjust the focal length coupled to the IS manually. I think that if I had a zoom, I'd do the same, only if I was shooting at low shutter speeds.

    With film cameras, the rule of thumb was don't go lower with the shutter than the inverse of the focal length : aka, don't shoot lower than 1/30 with a 35mm zoom and to be sure, go with at least 1/60. With a 75mm that would leave you at 1/60, or better 1/125.

    I have read that with the MFT halved sensor you have to shoot two stops faster (although this sounds a little too conservative to my ears) : aka at least 1/125 for 35mm and 1/250 for 75mm.

    The IS mecanism will give you these two stops back and perhaps a little more (at least on the E-P1, may be not so for the E-Pl1, from what the reviewers said). Then it probably depends upon each individual person too and how much coffee you drink.

    It is possible that when you are shooting near the limit of 1/125 the difference between setting the IS for 35 or for 70mm isn't very big.

    That said, when I forget to change the IS focal length I don't see much difference either, may be that you have to look at pixel level to see it. Also, it may be more important with longer lenses than with relatively short ones, shot near the tolerable limit of shutter speed.
    Last edited by Annna T; 15th May 2010 at 23:24.

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