Exposure variation wit 35-100 Olympus lens

[Mark Smith]

I have an issue with exposure change using the Olympus 35-100. Shooting white BKG at 100 units and when zooming out from 100 to 35 the lens seems to pull the exposure down 5 units. Lens is in manual, knee is not auto anything that would seem to be an auto mode is disabled but the issue persists. Any one got an idea as to why this is happening?

 

[Lpowell]

Check out my series of exposure fluctuation tests of the Olympus 35-100mm f.20 among other auto-focus zooms:

http://www.dvxuser.com/V6/showthrea...-during-zoom&p=2259656&viewfull=1#post2259656

 

[monkeyking]

Mark,
I started a thread a while back noting this problem with both olympus 14-35 and 35-100 lenses. Seems like an Olympus firmware issue to me but no solutions have been offered.

http://www.dvxuser.com/V6/showthread.php?234515-Olympus-14-35-35-100-zoom-lens-owners&highlight=

 

[Mac]

After several months of reading about this, it seems evident that either Panasonic or Olympus will need to fill this obvious hole with some lens choices.. They've got the optics already, they just need to build new housings for the most obvious of their lenses. Or, as suggested, at least provide a firmware fix if that's even possible (I doubt it personally).

In my case I have the luxury of not owning an AF100 yet (I moved it back to late March delivery) so I bought the cheapest zoom, the Zuiko 14-54. I'm sure I'll probably hate it when my camera arrives, but until something better comes along I'm not spending more money. It's wait and see as far as I'm concerned.

 

[wbrock001]

Or just get some nikon glass to tide you over and then sell it for a very minor loss and get whatever comes out.

 

[Glenn Przyborski]

I don't know if the Olympus people ever read this form or are even aware of who's buying their products and how they're used. Olympus makes some excellent lenses for 4/3... especially the 14mm-35mm F2 and the 35mm to 100mm F2. All they would have to do is issue a "video version" of their lens firmware that would eliminate the iris adjustments based on focal length. Otherwise you have to think of these lenses as just variable focal length, fixed lenses.

 

[Mac]

Or just get some nikon glass to tide you over and then sell it for a very minor loss and get whatever comes out.

I have 5 Leica-R lenses, including an Angenieux 45-90, that I'm anxious to use after over ten years in a drawer. I've sent them to Duclos for Cine-Mod. But, as a documentary filmmaker, I need a good, relatively fast (2.8 is okay) light weight parfocal zoom that works quickly and efficiently. And I know I'm not alone in this - this is potentially a HUGE market that would sell a lot of lenses.

 

[Benjamin Eckstein]

The iris adjustment is a bit of a PITA but these lenses are really the only game in town that do what they do, and it does that well, so I just deal with the iris issue.

 

[Mac]

Actually, the iris issue is minor, it is everything else that makes these lenses poor for a supposed "professional" camera.

I wrote "varifocal" originally in my post above because I was writing too fast. The problem is most of them ARE varifocal instead of parfocal. A documentary cameraman is in the habit of zooming in to focus and then framing... old habits die hard, and I've been doing that for over 40 years. Additionally - quiet and accurate adjustment of iris, smooth rotation of zoom (I don't care about a motor, but some do) and, yes, consistent iris when zooming would be nice too. There desperately need to be a good lens built specifically for this camera.

 

[Barry_Green]

You're describing a video lens. No stills camera lens performs like a real video lens. And there is no such thing as a video lens for any large sensor camera; not for nikon or canon, not for the red or the f35 or the Alexa. Just doesn't exist and that has been the main reason nobody has made a large sensor video camera before. The 14-140 was the first to sort of halfway get us there.

You probably will have to look at cinema lenses to get closer to what you're asking for. No auto functions at all but at least they have parfocal zoom with constant aperture and real focus and zoom and iris control.

 

[monkeyking]

I'm waiting for new lenses to be shown at NAB.

 

[Lpowell]

Olympus makes some excellent lenses for 4/3... especially the 14mm-35mm F2 and the 35mm to 100mm F2. All they would have to do is issue a "video version" of their lens firmware that would eliminate the iris adjustments based on focal length.

Unfortunately, engineering this kind of behavior in an electronic lens is a not as easy as it might seem. Unlike legacy manual focus zooms, which were mechanically designed to maintain constant aperture while zooming, there is no fixed relationship between aperture and focal length in a Four Thirds lens. These lenses are totally reliant on the camera's ability to dynamically adjust both lens aperture and focus. To maintain the appearance of a constant aperture while zooming, the camera's firmware would need to have near-stepless control over the iris and the processing power to instantly adjust iris settings numerous times a second.