Parfocal lenses for LS300

[Bill Edmunds]

I own the Lumix 35-100 f2.8 which is effectively par focal on my Panny GH3. Has anyone tested this lens with the LS300? I'm interested in other fast zoom lenses than are par focal and have smooth zoom rings. Any suggestions are appreciated!

[Steve Rosen]

Bill, I posted on another thread my various lenses that I've tried with the LS300. The 12-35 Lumix was not among them. However I do have a similar Olympus 12-40, and a Lumix 35-100.

Both of these lenses are - or at least "act" - parfocal on my old AF100, a friend's GH4 and my two BM Pocket Cinema Cameras. Sadly they don't on the JVC.

Same problem with several parfocal S16 lenses I own (one is WAY out), as well as the Metabones adapted EF 24-105 and EF-S 17-55 (which are nearly parfocal on the C100).

This has been frustrating me, since I am accustomed to zooming in to focus - and focusing wide, particularly at 12mm, is nearly impossible without using the 300's Expanded Focus feature - which doesn't export to my EVF...

My solution is to use the MFT zooms and take advantage of the 300's auto focus and face detect, which are quite good. I've never used AF before, but with this camera I need it or I tend to miss, even using my Gratical's peaking. It's not a perfect solution though.

My other option when shooting 1080 is to use selected primes, in my case Rokinons (and Leica-Rs), that cover the sensor with the VSM set at 100%. With a 24 Rokinon on the camera and a 35 or 85 in my vest pocket, I can handle almost any eventuality by zooming to 43% - and I have a constant 1.5 maximum aperture.

I am still confused as to why this one camera will not allow this variety of lenses to focus when they do on every other camera I've owned or used. I've been hoping that someone else would chime in with his or her experience - if for no other reason than to be sure my camera's flange to sense distance is correct - so thanks for posting the question.

Forgot to add--- I strongly advise against using the EF lenses with a Metabones Smart adapter. The 17-55 is fantastic with a speedbooster on the Pocket Cameras, but the Olympus 12-40 is much better on the LS300 - And don't even ask me about the 24-105. I was pretty happy with it on my C100, but it's pretty horrible on this camera - the out of focus areas are really ugly, it's so soft it's difficult to focus with peaking, AF doesn't work at all - and worst of all, it seems to lose a full stop when zoomed in on the JVC - it never seemed that bad on the Canon.

[Stephen Brenner]

Steve,

(referring back to a previous thread)
Did you try adjusting the backfocus on your 12-120 and 15-150 lenses with the LS300?

Steve

[Steve Rosen]

Stephen: No, I don't want to do it and make them unusable on my Pocket Cameras or my Aaton (which needs an airing once in a while)... I will live with the MFT and Rokinon lenses, they work... but I do miss a good manual 10x1 zoom.

In fact, during the AF100 wars, I was constantly pleading for a lens manufacturer to introduce an affordable MFT manual zoom lens - manual iris and focus - since Rokinon and others were doing it with primes... Now I hope some entity will do that with EF mount, since it's being utilized on so many cameras. But people are auto-everything now, it probably won't happen.

[Noa Put]

Originally Posted by Bill Edmunds

I own the Lumix 35-100 f2.8 which is effectively par focal on my Panny GH3. Has anyone tested this lens with the LS300? I'm interested in other fast zoom lenses than are par focal and have smooth zoom rings. Any suggestions are appreciated!

I think Joachim explained it nicely here: http://www.dvinfo.net/forum/jvc-4k-p...ml#post1902617 and here: http://www.dvinfo.net/forum/jvc-4k-p...ml#post1902713 why photolenses are not parfocal, if you have one then you are just lucky and if you want them to be parfocal across other m4/3 camera's it's just wishfull thinking.
It is however possible to build one, like Sony did with their 28-135mm lens, but it's never going to be a cheap lens, maybe one day Panasonic will make a parfocal lens but until then it is what it is.

[Steve Rosen]

Bill's answer, although certainly correct in essence, still does not answer the core question of why a variety of lenses - different makes and manufacture - some quite expensive original parfocal designs - work on every single other camera as parfocal (or in the case of still lenses, seeming parfocal)...

...but do not work that way on one, and only one, camera - the LS300.

Some of the lenses in question (particularly my T2.6 Canon 12-120 Flourite and T2.8 Cooke 10.4-52) are WAY out - so far that you can't focus to infinity when wide - while some are only slightly out, like the very old design T3.1 Angenieux 15-150 and the very new design f2.8 Olympus 12-40 Pro.

I thought that it might relate to the inherent resolution of the LS, which is quite good - that perhaps it was displaying an aberration that was always there but hadn't shown up before on the less sharp cameras - until I had a friend try the Olympus on his GH4, and it worked perfectly, exporting 4K to an 80" screen. Same with the Cooke (although with an S16 image circle) - two completely different lens designs - one a $12,500 S16 Cine lens, the other a $1,000 MFT still lens.

I called an old friend from UCLA, a DP now who, although not a lens expert, has used almost every lens ever made on almost every camera ever made, including some of mine, and he can't come up with a good guess at an answer either.

[Joachim Claus]

Steve,

I think the reason of not being parfocal with the LS300 is the Micro Four Third camera lens mount. This lens mount is designed to a specific distance between lens mount surface and sensor surface. If you use a full format lens, it may have a different distance and hence you need to adjust the sharpness (distance between focal point and sensor surface) to get a sharp picture. To my knowledge it should work fine, if you use MFT-lenses of other manufacturers. But even then, you may observe a sharpness shift when zooming.

Joachim

[Steve Rosen]

Well, both my Pockets, my friend's GH4 and my former AF100 all have MFT mounts. All the lenses I've listed work as parfocal, or close to parfocal, on those cameras.

In fact, after Panasonic's pitiful abandonment of the AF line, the MFT mount is one of the main reasons I opted for the LS300 rather than another Canon, or a jump to Sony.

I've owned some sort of motion picture camera since 1964. I've had lenses collimated often over the years, originally at Century, then Aaton in Burbank, then ZGC in New Jersey. Never in my experience have I had a well-maintained lens, let alone a bunch of lenses, that work well on one professional camera, and don't on another.

Neither have I had the experience of two lenses, i.e. the Canon 12-120 and the Angenieux 15-150, work identically on all other cameras, but radically differently from each other on one, and only one, other make of camera. The Canon goes way out of focus when zoomed back, and it takes a clockwise rotation to bring it close to infinity (it never reaches infinity). The Angenieux only goes slightly out, but requires a COUNTERclockwise rotation. BTW, both are using the same (collimated) Aaton to MFT adapter.

I'm not arguing with you or anyone else - I just don't think the answer is as simple and straight-forward as some seem to think. There must be something radically different about the surface glass of the sensor in the LS300 - that can be the only answer for the behavior I'm experiencing.

Unless there is something wrong with my particular camera. That's why I keep asking for feedback from others who may have tried several zooms with their's.

[Joachim Claus]

Steve,
I see your point, and it is in fact mysterious why your MFT lenses work nicely on other MFT-mount cameras but not at the LS300. My advice would be to contact your dealer at their location and test your lenses with a second LS300. If it shows the same characteristic, then there is something wrong in the LS300 design. If this gives you nice parfocal, then it is a fault with your camera and a case for repair at JVC.

Best regards,
Joachim

[Steve Rosen]

Joachim: Your advice is good, and reflects my previous commitment to always buy from an established Cine-dedicated source, like AbelCine in Burbank (formerly Aaton) or Birns and Sawyer in Hollywood.

However, when this techno-centric runaway train left the station in 2007 - when it seemingly became necessary to buy new gear after every NAB - I swore to never pay more than 5 grand for a camera again, and switched my allegiance to a box store - the old standby, B&H.

Now I regret it - I miss the days when I could walk into Birns and Sawyer, set my camera on the counter and have a knowledgeable discussion with a person from "the back" who actually knew what he or she was talking about.

There were some real advantages to the good old days.

BTW, just to throw another wrench in the works, all of my newly acquired MFT mount Rokinon primes focus perfectly to infinity - In fact, the 24, which has a weird focus-past-infinity stop, focuses at infinely exactly on the line scribed on the lens (if you've ever used one you'll know what I mean)... So that would indicate to me that my camera's back-focus is correct.

[Lee Powell]

Originally Posted by Steve Rosen

BTW, just to throw another wrench in the works, all of my newly acquired MFT mount Rokinon primes focus perfectly to infinity - In fact, the 24, which has a weird focus-past-infinity stop, focuses at infinely exactly on the line scribed on the lens (if you've ever used one you'll know what I mean)... So that would indicate to me that my camera's back-focus is correct.

That also suggests the problem you're seeing may lie in the flange length of the MFT adapters you're using to mount your non-MFT lenses to the LS300. If an adapted lens won't focus out to infinity, the flange length is incorrect.

On the parfocal lens front, there's an obscure Sigma Four Thirds zoom that occasionally pops up on Ebay:

Sigma AF 18-50mm f/2.8 EX DC macro - Review / Lab Test Report

This 18-50mm f2.8 zoom was more commonly made in Nikon and Canon mounts, which would work with manual focus and aperture control on the LS300. What's notable about the legacy Four Thirds version is that it can be mounted on the LS300 with an active MFT adapter, and operated electronically with in-camera controls. Its auto-focus behavior is actually quite smooth, not too fast or slow, and free of hunting in decent light. Aperture control, however, is problematic. The LS300 is able to adjust lens aperture in both auto and manual modes, but the viewfinder aperture display is erratic and inaccurate, no doubt a firmware compatibiliy issue. It's easiest to just set the LS300 to full-auto mode and let it handle focus and exposure while you take advantage of the lens' 18-50mm parfocal zoom range. Unlike the iris flicker that plagues Panasonic and Olympus zooms, the Sigma's exposure remains stable while zooming.

[Steve Rosen]

Lee, thanks for your reply... I don't want to constantly seem argumentative, but two of my zooms, the 12-40 Olympus and the 35-100 Lumix, are native MFT, and they work as parfocal lenses on my Pocket Cameras, and also worked that way on the AF100, which I originally bought them for. (I wish I could get images to post on this site so I could demonstrate)...

My continuing question is - why do a my collection of (eight) zoom lenses act differently on the LS300 than on any other cameras?

[Lee Powell]

Originally Posted by Steve Rosen

...two of my zooms, the 12-40 Olympus and the 35-100 Lumix, are native MFT, and they work as parfocal lenses on my Pocket Cameras, and also worked that way on the AF100...

Are you shooting in continuous auto-focus mode while zooming with these MFT lenses? While I haven't tested those two models, I used a wide variety of Panasonic and Olympus MFT lenses on the GH2 and AF100, and I wouldn't consider any of them truly parfocal. MFT lenses aren't designed to be mechanically parfocal, they rely on electronic control via the camera to continually readjust iris and focus while zooming. Perhaps the difference you're seeing with the LS300 is because it isn't attempting to maintain focus while zooming? How do these zooms perform when you enable auto-focus on the LS300?

[Steve Rosen]

Lee - Actually I've never even turned on auto focus on any camera until the LS300, and then only after realizing that these lenses were shifting focus when zoomed out and I was losing my wide shots.

I'm aware that no still zoom lenses are truly parfocal, that's why I don't care much for them. However, using the AF100 as a model, both the Olympus and the Lumix "act" parfocal when zoomed out, even wide open at f2.8. Now it may be that that camera, even when not set on AF, actually adjusts itself electronically for the focus point when zooming - I have noticed a moment of softness with a snap zoom. I've seen the same behavior with the 24-105 and 17-55 Canons on the C100.

Okay, push the AF100 aside and pop a lens on the diminutive $1000 Pocket Camera. It also seems to hold focus well when zoomed out at 2.8 - which is odd, because you wouldn't think a camera that tiny and cheap would have the electronically compensating behavior.

Unfortunately on the LS300 (which I generally think is a great camera for the price) they don't hold focus, even when stopped down to f5-6 or 8 - and out of focus is really ugly with theses lenses. When set to AF, they work quite well - given that there aren't prominent objects in the foreground like tree branches, passing cars or lamps - which there almost always seem to be in my shots. *FYI - I have taped a little extension to the User button for AF, so I can feel it easily and turn AF on and off without taking my eye from the viewfinder. This helps some.

In my mind AF is an amateur practice anyway, and so I've switched to manual primes for use on this camera, with occasional use of the 12-40.

Unfortunately no one make a nice manual short parfocal zoom. I've been begging for one for years, but the demand for auto-everything has prevailed.

[William Hohauser]

Here's a test that may or may not prove anything but I am interested since I am thinking of replacing one of my GH cameras with the LS300.

Take one of your primes and place it on the BMPC or one of your GH cameras. Focus on an object as close to the camera as the lens allows it to be sharp. Measure how far away from the front of the lens the object is. Switch the lens to the LS300 and see if the distance is the same. Try it with one of the zooms as well. If it's the same then I am barking up the wrong tree again. If it's different then the theory that the camera construction is somehow different gains strength.