List of parfocal zoom lenses for MFT

Since almost none of the reviews for MFT zoom lenses seem to indicate whether the lens is parfocal (focus point does not change while zooming) I would like to crowdsource a list of MFT zoom objectives which the users themselves have tested. For me parfocality is important because of the way I shoot video: Set the aperture to f/8, set the focus point to a fixed distance and constantly track the subject across the entire zoom range (motorsports on a closed track). This cannot be done with a varifocal lens as I have found out the hard way (I really wanted to keep the Panasonic 45-175).

Below are the findings from my own personal experience. I would appreciate if users who have their own personal experience would add to these lists. I don't know if the body has an effect, maybe Oly bodies with Oly lenses can sometimes autocompensate, but these tests were done using the E-M5 Mark II. The Panasonic 12-60 lenses would seem like great replacements for the 12-40 Pro due to the weight savings but if they are varifocal they are useless for me.

Parfocal (or close to it) MFT zoom lenses:

• Olympus M.Zuiko 12-40/2.8 Pro
• Olympus M.Zuiko 40-150/4-5.6R

Varifocal MFT zoom lenses:

• Olympus M.Zuiko 14-150/4-5.6 II
• Panasonic Lumix G X Vario 45-175 PZ

Parfocal (or close to it) MFT zoom lenses:

• Olympus M.Zuiko 12-40/2.8 Pro
• Olympus M.Zuiko 40-150/4-5.6R

Some say that these are not actually parfocal but with some cameras, like the E-M5, their AF mechanism compensates for zoom movements to keep the subject in focus. If true, the parfocality may only work on some bodies and not on others. See https://www.dpreview.com/forums/post/59090635

When you search this forum for 'parfocal' you'll find some interesting comments, for instance that the (easily adaptable Four Thirds lens) Oly Zuiko 14-35mm f/2 SHG is parfocal (or close to it, according to others).

Anyway, I hope you manage to compile a full list here!

The zoom lenses are not parfocal, not even close.

But if you AF (with AF-S) and then zoom the camera will keep changing the focus to keep the focus distance roughly the same.

If you AF and then switch to MF and start zooming you will see that the image goes way out of focus.

The biggest differences you will see is between camera-lens combinations that support this "software parfocal" system and those that don't.

Paul De Bra wrote:

The biggest differences you will see is between camera-lens combinations that support this "software parfocal" system and those that don't.

That's what I was afraid of. Even the list of software assisted combos might still be useful if anyone has experience besides the two I listed. I wonder what cost-cutting decision led to the Oly 14-150 II not being on the list. It would have been a great all-rounder for me otherwise.

When you focus and then change the zoom on the subject the software parfocal feature means the new af operation is a very small correction and therefore faster. It is not that refocus would no longer needed. (It is not 100% precise after all.)

Paul De Bra wrote:

The zoom lenses are not parfocal, not even close.

But if you AF (with AF-S) and then zoom the camera will keep changing the focus to keep the focus distance roughly the same.

If you AF and then switch to MF and start zooming you will see that the image goes way out of focus.

Actually this is not true. At least on Panasonic bodies, the autofocus mechanism corrects for parfocality even in manual focus. To be clear, it does not use autofocus, just the autofocus motor.  In fact, when zooming on a stationary subject, it is very reasonable to switch off autofocus, as this can screw the parfocality correction.

Also, when testing parfocality, it is extremely important to set the focus when zoomed in. It is not possible to set focus precisely enough when zoomed out.

When I switch my lens to MF (with the focus ring/clutch on the 12-40, probably on the others as well but I don't have them with me) on my E-M5 the noise of the AF adjustments while zooming is still there and the image remains more or less in focus. The same when you set MF on the camera instead of or in addition to on the lens.

To see that the lens is really not parfocal you need to zoom with the camera powered off it seems.

qcjulle wrote:

Since almost none of the reviews for MFT zoom lenses seem to indicate whether the lens is parfocal (focus point does not change while zooming) I would like to crowdsource a list of MFT zoom objectives which the users themselves have tested.

Now you've done it.  I have 6 lenses to test...maybe tomorrow.