Test with some measurements

Big note - it is individual old lens review, and it looks like not best sample.

https://www.ephotozine.com/article/vivitar-28-200mm-f-3-5-5-3-macro-focusing-zoom-vintage-lens-review-33955

Not sure why that guy is so surprised. There have been about a bazillion really sharp ~50mm f/2 lenses over the years and a lot of them are cheap now. The Pentax SMC series were also really good and my Konica hexanon was also pretty great!

Depends which ones you mean. Most of those are 2/3" format lenses, which don't cover Super 16. Others are 1" format, but impossible to mount to Micro Four Thirds. The old Cosmicar 1" vidicon lenses are quite nice.

Took this first shot in fading autumn light of one of my vine leaves; Sigma SD1, $25 Hidden Gem lens Industar N61, ISO 200, F4.0. (Set to 1 meter, for all the good that'll do it)

Notice how it really is Macro only; part of the vine leaf is still out-of focus so from now on it's bright light and macro shots of flowers for me on the SIgma camera, ordinary pics (like shot 2) will come from the GH2 :-)

When have you ever known VK to back down from his original statement? Resistance is futile.

That lens is for a Leica M39 screw mount. It has a much smaller flange distance than any SLR, so it can't fit a Sigma SA mount without correctional optical elements. Or it will be a macro without being meant to be one.

MFT has a much smaller flange distance and the lens can be adapted correctly, reaching infinity. If you want macro, you'll need extra distance rings.

wow, didn't intend to kick off such a discussion, hope you guys are still enjoying yourselves! thanks for the insight though, balazer! you wrote that the soligor and the tokina are basically the same design, yet you don't own them as far as I understand? have you had a chance to try them? and, as I heard many good things about the push/pull contax zooms (apart from being push/pull): do you have an idea on how they compare/mix/match?

thanks again!

Vitaliy, this seems to be a language problem. Parfocal doesn't mean perfectly parfocal. There are degrees of parfocal-ness, just like there are degrees of sharpness. Even if a lens isn't perfectly sharp, it was still designed to be sharp (usually). How sharp is another question entirely that has to do with the design, the manufacturing, the physical condition, and the focusing. Zoom lenses are designed to be parfocal. How parfocal is another question entirely that has to do with the design, the manufacturing, the physical condition, and the back focusing.

Variable focal length lenses can all be classified cleanly into "zoom" or "varifocal", according to their designs, with the vast majority being zoom lenses. The degree of parfocalness is a matter of lens performance. Just like everything else about a lens, some perform well and some perform poorly. I test at 1080p, not 4k, and only a few of my old zoom lenses are very close to being parfocal near their widest aperture settings. (and I've tested way more than 20) It depends very very much on the back focus. If you don't have an integrated back focus adjustment, a helicoid adapter, or do careful shimming of the lens, you will find the vast majority to be not very close to parfocal, due to the lens itself not having a perfect flange focal distance, or more often due to the adapter having the wrong flange focal distance. But they are still parfocal lenses by design. Fix the back focus and set the aperture somewhat smaller, and the vast majority of those old zoom lenses become fairly close to being perfectly parfocal.

If you are interested trying some old zoom lenses and seeing how parfocal the lenses are, you absolutely need a way to adjust the back focus.

I have more lenses than I can list. If it's manual focus, two-touch, and constant aperture in Minolta SR mount or C-mount, I probably have it, so go ahead and ask me. I don't have that Soligor, but I do have its little brother, the 45-150 f/3.5 C/D. It's made by Tokina in 1976, and it's a beautiful lens.

The Soligor 70-210 f/3.5 C/D is the same as the Tokina RMC 70-210 f/3.5, from about 1977. Constant aperture photographic zoom lenses become less common starting around 1980, due to the appearance of automatic through-the-lens "final check" metering.

An example of a focus-by-wire that is only electronically parfocal is the Lumux G Vario 14-140 f/4.0.

The vast majority of photographic zoom lenses are parfocal. I have seen only a small number of varifocal photographic lenses, and an even smaller number of photographic varifocal lenses with the term "zoom" misapplied. Yes, I am talking about old still lenses.

You will know when you have found a varifocal lens. The focus shifts hugely as you zoom in or out, and the focus distance scale markings indicate a shift over the range of focal lengths. The Makinon/Hanimex 28-80 f/3.5 is one example of a varifocal photographic lens that comes to mind.

I think you have simply encountered a number of lenses for which the back focus wasn't adjusted quite right, or that were less than perfectly parfocal due to mechanical imprecision of the movement. But they are still zoom lenses and they're still parfocal. Zoom lenses are not zoom lenses by accident. The design of a zoom lens has an extra group movement. If you leave that movement out, you get a lens that is very very far from being parfocal.

In the modern focus-by-wire zoom lens, there are some designs which are parfocal only eletronically: they lose focus briefly as you zoom in or out, and then regain focus when the focus motor refocuses (with no action on your part, and even in manual focus mode). They are still parfocal and still zoom lenses, but in a less desirable sense than the mechanically parfocal zoom lens.

It is a correct statement. A non-parfocal "zoom" lens is not a zoom lens at all. That's a varifocal lens.