List of Canon parafocal zooms (anywhere?)

[RogerMcC]

I am stunned that Canon does not provide this information for pre-sales concerns.

I've looked in the Canon museum and the EF Lens chart .pdf but have yet to find the information. Does it exist?

Which lenses are known to be parafocal?

Thanks!
Roger

[ChuckWestfall]

Hi, Roger:

First, you're correct that Canon Inc. doesn't provide such a list. Second, the term you're referring to is parfocal, not parafocal. Third, based on practical experience, the list of parfocal zooms in the Canon EF lens line-up is essentially limited to the fixed-aperture L-series category and front-focusing zoom lenses. The current products include:

EF 16-35mm f/2.8L USM
EF 17-40mm f/4L USM
EF 24-70mm f/2.8L USM
EF 70-200mm f/2.8L USM
EF 70-200mm f/2.8L IS USM
EF 70-200mm f/4L USM
EF 75-300mm f/4-5.6 IS USM
EF 75-300mm f/4-5.6 III USM
EF 75-300mm f/4-5.6 III
EF 90-300mm f/4.5-5.6 USM
EF 90-300mm f/4.5-5.6

Discontinued lenses in this category include:

EF 17-35mm f/2.8L USM
EF 20-35mm f/2.8L
EF 28-70mm f/2.8L USM
EF 28-80mm f/2.8-4L USM
EF 50-200mm f/3.5-4.5 USM
EF 50-200mm f/3.5-4.5
EF 70-210mm f/4
EF 75-300mm f/4-5.6 II USM
EF 75-300mm f/4-5.6 II
EF 75-300mm f/4-5.6 USM
EF 75-300mm f/4-5.6
EF 80-200mm f/2.8L
EF 100-300mm f/5.6L
EF 100-300mm f/5.6

EF zoom lenses with Super Inner Cam focusing, which include most of the non-L zooms introduced from 1990 onwards as well as the EF 35-350mm f/3.5-5.6L USM and the EF 100-400mm f/4.5-5.6L IS USM, are not parfocal.

Hope this helps!

[RogerMcC]

Thank you very much Chuck!

Yes, this list is ~very~ helpful.

It documents what is (for me) probably the most important benefit of an L lens.

Roger

[David_Pennybaker]

I know that MY 70-200/2.8 IS is NOT parfocal. At least not at short distances (say 20 feet or less).

It's easy enough to test. Focus on something at 200mm. Then, zoom back to 70mm, and refocus.

Has anybody else tried this?

I will say that at much longer distances (near infinity), the lens appears to be parfocal. But this may simply be due to the larger DOF.

[Adam Wade]

David, I'll be very surprised if you can prove Chuck wrong.

Does your test take into account the range of precision of the AF?

[David_Pennybaker]

I wasn't trying to prove anybody wrong, just offering up the fact that my 70-200/2.8 IS is clearly not parfocal at close distances.

I've actuallly used the "focus at 200mm, then zoom back to 70mm" to get a more precise focus before, and it seems to work well when the distance is long enough.

But a few weeks ago, somebody on another forum posted about how these Canon zooms are NOT parfocal. (The manual DOES warn against focusing and then rezooming, after all).

So, I decided to check for myself, shooting some objects across the room. Maybe 10 to 15 feet away.

At 200mm, the AF locked on, and the object looked in focus. When I zoomed out to 70mm, the object was clearly no longer in focus. Hitting the AF button again refocused the lens.

I asked about this on another forum. A guy responded that HIS lens seemed to be parfocal at close ditances, but NOT at large distances.

So, "on average", maybe our lenses ARE parfocal?

[RogerMcC]

Suppose you focus at 200mm and then zoom down to 70mm and then back again to 200mm with the focus locked. Is the subject ~still~ in focus?

Roger