parfocal zoom

[Bill Kerrigan]

According to this video interview below, the Sony FE 70-200mm f/4.0 G is parfocal.
Is this true? Does anyone know more details?
NAB Interview: Sony's Juan Martinez on the NEX-FS700R and Latest E-Mount Lenses - Streaming Media Producer

I'd be willing to lose 1 stop in exchange for parfocal... but description in the B&H listing doesn't mention parfocal.
http://www.bhphotovideo.com/c/product/1029862-REG/sony_sel70200g_70_200mm_f_4_5_6_g_lens.html
Bill Kerrigan,
Montreal Quebec Canada
Director of Photography

[Shawn Lam]

Hey Bill,
I have never seen a manufacturer list a lens as being parfocal, which is unfortunate as this is such an important consideration for videographers.

I did test the FE 70-200mm f/4 G at NAB 2014 just before I shot the interview with Juan and I can confirm that it is a parfocal lens. The FE 24-70 f/4 is parfocal as well.

Regards,
Shawn

[J. David Pope]

Sony describes the Sony FE PZ 28-135mm f/4 G OSS Lens as:

"Maintains plane of focus while zooming and maintains field of view while focusing (important for video)."

Funny, but for most of my shooting career I never knew there were zooms that are NOT parfocal. All I ever operated were broadcast tv zooms. I didn't realize how few still photographers focus manually, so it never occurred to me that the still shooters would be using zooms that require re-focusing with each change of focal length.

The Sony marketing for that same lens says "Angle of view variations while focusing (breathing) and axial displacement while zooming have been reduced ". Any idea what "axial displacement" means in terms of photography? The Google isn't of much help.

[Chris Andrikakis]

Originally Posted by J. David Pope

Sony describes the Sony FE PZ 28-135mm f/4 G OSS Lens as:

"Maintains plane of focus while zooming and maintains field of view while focusing (important for video)."

Funny, but for most of my shooting career I never knew there were zooms that are NOT parfocal. All I ever operated were broadcast tv zooms. I didn't realize how few still photographers focus manually, so it never occurred to me that the still shooters would be using zooms that require re-focusing with each change of focal length.

The Sony marketing for that same lens says "Angle of view variations while focusing (breathing) and axial displacement while zooming have been reduced ". Any idea what "axial displacement" means in terms of photography? The Google isn't of much help.

I found this (Buy - Arri / Zeiss UltraPrime T1.9 / 135mm PL mount prime lens with IMPERIAL scale (K2.52133.0)) which may be relevant:

"Iris and Focusing Rings without axial displacement
The rigid construction creates the prerequisite for an important advantage: the position of the gears for focus and iris does not move axially during focusing. External motor units thereby work more simply and with considerably increased reliability. Also, lens changing becomes much easier, faster and safer. "