Canon 24-70mm not constant 2.8?

[Kim Frank]

I just shot a Musicvideo with a lot of fast Zooms.
In post I recognized a brightness loss about a half stop
on the longer end of my new 24-70mm Zoom.
Made CC really complicated.
Is that normal (I don't hope so!)

 

[Scott Crawley]

The 24-70L is consistant from end to end. I don't know of any reason why the lens would loose light on the tele end, and it doesn't stop down on the wide end.

 

[Kim Frank]

Okay thanks...
Than I picked a bad one.

 

[Roberto Lequeux]

Others here have reported the similar findings.

 

[Kim Frank]

Called the shop where I bought it and he tried to explain to me, that this is normal.
He said that this would have to do with the film modus of the 5DII.
What to believe.
I'm going to give it a test picture vs. film,
but maybe someone knows.

 

[Kim Frank]

Others here have reported the similar findings.

Thanks Roberto, but does "the same" mean it's normal or its a faulty lense`?

 

[Roberto Lequeux]

the film modus of the 5DII.

The Whha?!

Smells like :icon_bs:

Thanks Roberto, but does "the same" mean it's normal or its a faulty lense`?

It would seem that it is "normal". I'll try to post a comparison for you.

 

[Roberto Lequeux]

These are 20% horizontal but full vertical crops with the same region roughly in the same area of the image circle. Same distance and lighting of course. RGB measurements from the PS eyedropper tool.

 

[Kim Frank]

Thank you very much!
That's exactly what I mean.
And I always thoght it would be constant.

 

[Roberto Lequeux]

Might be worth pointing out the obvious, one measurement won't be an very accurate quantification of the light loss.

 

[Stephen Williams]

If you stop down to T4 does the same problem happen? Most 2/3" ENG lenses suffer wide open. Motion picture lenses cost a lot of money, this is one of the issues they have sort out.

 

[Roberto Lequeux]

That comparison I posted was at f/3.5 which is probably around T4.

 

[Stephen Williams]

That comparison I posted was at f/3.5 which is probably around T4.

Try 1 stop down from wide open, I would expect it to be fine.

 

[Kim Frank]

Well the lense has a F 2.8.
The video I shot was at a 5.6
and the shift was there.
But I'll give it another shot

 

[Michael Hastings]

These are 20% horizontal but full vertical crops with the same region roughly in the same area of the image circle. Same distance and lighting of course. RGB measurements from the PS eyedropper tool.

What do those numbers translate to in F stops?

 

[Jannard]

That's just one of the reasons you pay more for a cine zoom.

Jim

 

[Matthew Duclos]

That's just one of the reasons you pay more for a cine zoom.

Jim

EXACTLY!!!!
Thank you Jim.

 

[Kim Frank]

What would be a full frame cine zoom with a T3 and how much would it cost.
I'd say correcting half a stop difference in post is more in my budget range.

 

[Scott Crawley]

He said that this would have to do with the film modus of the 5DII.

I presume he was referring to the shooting mode and/or metering mode.

 

[Kim Frank]

Don't know if I understand?
Always talking manual settings.
No auto metering. But he was wrong.
It's a lens issue, not camera or shooting mode