Flickers when zooming in and out.

G

Gene Sung

Veteran
I just bought a refurbished Canon EF 70-300mm f4 to f5.6 from Samy's Camera (reputable).

I went out to do some tests on it, since it is refurbished.

I noticed that when zooming in or out on a shot (from 300mm to 70mm and back), there is a series of quick flickers that happen over the course of the zoom. I actually hear a little "Click" sound when it flickers.

Is this because it is a variable aperture zoom (f4 to f5.6)? Or am I missing a setting or doing something wrong? Is there anything that can be done so I don't get the series of quick flickers while zooming?

Here's a quicktime of what is happening.

http://www.builtbyugene.com/mov_clients/test_flicker2.mov

Thanks for any help.
 
I would also like to know what's going on. I get the same thing from my new 70 - 300...something happens when you zoom in and out. The iris is doing something even though you have it all full manual.
 
It is because that zoom is not constant aperture.

Doesnt matter if it is full manual or not, the lens will stop down as you zoom.

The only thing you can do to stop it is start at an aperture slower than the slowest rated on the zoom. In the OP case 5.6, which is about a coffee straw, but will prevent the lens having to change during a zoom.
 
What about people who have the Kit lens 28 to 135 or the 18 to 135. Do you guys get that flicker also? Or is it only with the much longer zooms like the 70 to 300?
 
I pretty much figured it was the variable aperture that was causing the video flicker. I'm sure this is probably old news to a lot of you.

So I took my EF 70-300mm down to Samy's and we tested it on their camera and also used one of their identical lenses, and the flicker was there every time.

The sales people were curious (they didn't know this problem existed with Video), so they tried several other Canon Variable aperture zooms (including the kit lense), and they all had the exact same flicker problem. We tried several Constant aperture zooms, and NO problems at all.

So I guess the moral of the story is, if you plan to do any zooms and don't want flickers, get a constant aperture zoom.

Kind of ironic that with certain zooms, you can't really do a clean zoom.
 
It's not ironic at all. This is where the convergence of still and video hasn't quite happened yet. We're using lenses to do things that they weren't designed to do: capture video.

My hope is that in the near future we'll start to see "hybrid" lenses for stills/video that match up with the technology in the bodies themselves.
 
One kind of funny story about this situation. I called Canon Tech Support and they insisted till they were BLUE in the face that there are absolutely NO flicker issues with variable aperture zooms and DSLR video.

I told the tech support agent that another 7D owner (Octopie_Films) on DVXUSER.com reported the exact same problem, and she told me that people on photo forums usually have NO idea about what's going on with cameras. LOL. The tech agent kept insisting over and over again, that myself, the 4 salespeople at the camera store and octopai_films were wrong. LOL.
 
gene_can_sing said:
One kind of funny story about this situation. I called Canon Tech Support and they insisted till they were BLUE in the face that there are absolutely NO flicker issues with variable aperture zooms and DSLR video.
Click to expand...


Well, technically they are right. There is no "flicker" issue. The lens is changing aperture just like it is supposed too. There is a change in exposure related to aperture closing, but there is no flicker.
 
Strangely though the picture through my 18-85IS still flickers if I set the aperture to f 5.6, which is well out of the way of its floating point iris... why would this be? Shouldn't it be 5.6 all the way across the zoom range when stopped down so much?
 
rallymatt said:
Well, technically they are right. There is no "flicker" issue. The lens is changing aperture just like it is supposed too. There is a change in exposure related to aperture closing, but there is no flicker.
Click to expand...

There is a DEFINITE flicker issue with any lens that has a variable aperture. Eventhough you set it to f8, it will flicker when zooming in videomode 1080p. Setting it to 720p fixes it (odd). Also when you use a constant aperture zoom there is no flicker.

But variable lenses definitely have a flicker issue that is more than just a change in exposure because it happens even when you lock the aperture down to like f8. I have only the Canon kitt lens to test but that does it and my Tamron constant zoom doesn't. This is why some people report but some don't.
 
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