Are all Zooms Soft wide open?

[Richard Lowther]

Hi,
I have a question about zoom lenses, as I am trying to figure out if I can use zooms when I am going to use stills from the footage we shoot The reason I am asking is because:
We needed to get some still frames from the live footage we recently shot. We used on this shoot an old 20-100 Cook mark 2 on an MX Red we noticed that later in the day when the sun was going down and the lens was wider open the stills were really soft. After we took the ND out and the lens was more closed the stills were sharp again.
Is this normal for older Cook Zooms or is this normal for all zooms?

Thanks
Richard

 

[David Mullen ASC]

It's normal for most lenses, not just zooms, but old zooms in particular look sharper in the f/5.6 range.

The old rule is that most lenses are best closed-down two-stops from wide-open. Now some lens manufacturers like Zeiss claim that lenses like the Master Primes or DigiPrimes are optimized for wide-open shooting, though I'm not sure that is true... but certainly they hold up much better than other lenses shot wide-open. However, I still hold in general to the old rule, any lens is going to be sharper if closed down a little. But especially a Cooke 20-100mm...

 

[Adam Eden]

I have the new arri zeiss light weight zoom 2 and it is incredibly sharp at all stops.

 

[Richard Lowther]

Thanks for your help

 

[Gunleik Groven]

What has been said is right, but in addition to this, it could be a slight backfocus issue...

 

[Kalani Prince]

I was pleasantly surprised with Canon's 14mm L prime at 2.8 Pretty nice to say the least.. At F.8 it was a sharp little puppy with very little barrel distortion.

 

[Mike 'Fireman' Ross]

I think the key phrase was 'old Cooke' and I think David Mullen was 100% correct; my 'old Cooke' is exactly the same: wide-open and/or the extreme ends of the zoom range aren't the best place to be.

If I ever get hold of a Master Zoom I'd be happy to confirm more modern lenses are better in that respect!

Mike

 

[David W. Jones]

My Cooke 20-100 starts to get real sharp at the f4-5.6 split.
I shoot wide open into the sun for soft flare fx.

All the Best!

Dave

 

[Nick Gardner]

My 20-100 is pretty snappy. How was focus set, and when was the last time it was serviced? While it is true that all lenses are sharper stopped down a bit, the 5:1 is hardly useless wide open.

Nick

 

[David Mullen ASC]

Season 1 and 2 of "Big Love" were all shot on a Cooke 20-100, mostly wide-open. James Glennon picked that approach early on as a way of flattering the actors without lens diffusion. Plus it's a great focal-length range, we shot masters in the 27-35mm range and always ended up at 100mm by the end for coverage.

 

[Evin Grant]

I'm shooting a show primarily on the Cooke 18-100 and 25-250 MIIs right now, but we use the Angie Rouges for the green screen because they are noticeably sharper for compositing. Still, they do cut together well once it's all said and done. It's a bright kids show so we're in the T4.5-6.3 range most of the time, the lenses look sharp but flattering.