Okay to use Metabones speedbooster + lens adapter?

[cestlefun17]

I have a couple of Mamiya 645 lenses that I would like to use on my Panasonic GH4 (Micro-4/3) camera to shoot video.

Is this a good idea or will I run into issues?

Mamiya 645 lens + Mamiya 645 to Canon EF adapter + Metabones Speedbooster Canon EF to Micro-4/3

 

[petrochemist]

I suspect the 645 lenses might be heavy enough that you'd want to support it carefully, but other than the strain it might put on mounts it should work fine. I use Pentax K mount lenses & OM mount lenses on my EF mount focal reducer without difficulties.

 

[Derrel]

I have a couple of Mamiya 645 lenses that I would like to use on my Panasonic GH4 (Micro-4/3) camera to shoot video.

Is this a good idea or will I run into issues?

Mamiya 645 lens + Mamiya 645 to Canon EF adapter + Metabones Speedbooster Canon EF to Micro-4/3

That type of lash-up is pretty common these days, as can be seen if one hangs out online where a lot of adapted lens shooters hang out. dPreview just launched an "Adapted Lens Talk" sub-forum this week, and browsing the site, you'll see similar lens to adapter to second adapter to Metabones rig-ups mentioned. I really do not think you'd have much of an issue with image quality in motion video; each field is seen only briefly, the subjects are moving the camera's moving, and so on. Video is not really that critical of lens quality. Have you seen the YouTube comparison of Zeiss cinema prime lenses, and another band of cinema lenses, compared against low-cost 35mm slr system lenses? In the blind testing, I found it impossible to separate a $30,000 cinema lens from a $119 Canon 50 EF 1.8 on motion video images. Of course, I was watching on YouTube, not on say a 70-inch flatscreen TV in 4k.

Lensrentals.com's adapter testing shows that one adapter can lower total performance (resolving ability) substantially, and your setup will have multiple interfaces: camera mount, adapter rear,adapter front, 2nd adapter rear, 2nd adapter front,metabones rear, metabones front, lens rear. Seems like eight separate surfaces to me if I have my brain set correctly today. So, a lot of links....so yeah, definitely support this set-up from underneath.

 

[petrochemist]

I have a couple of Mamiya 645 lenses that I would like to use on my Panasonic GH4 (Micro-4/3) camera to shoot video.

Is this a good idea or will I run into issues?

Mamiya 645 lens + Mamiya 645 to Canon EF adapter + Metabones Speedbooster Canon EF to Micro-4/3

<snip>
Lensrentals.com's adapter testing shows that one adapter can lower total performance (resolving ability) substantially, and your setup will have multiple interfaces: camera mount, adapter rear,adapter front, 2nd adapter rear, 2nd adapter front,metabones rear, metabones front, lens rear. Seems like eight separate surfaces to me if I have my brain set correctly today. So, a lot of links....so yeah, definitely support this set-up from underneath.

Derrel the metabones IS the second adapter so you've got two extra surfaces.

I don't see how an adapter without optical elements can lower resolving ability. they're just extension tubes with different mounts on either side. Badly made ones could introduce minor shift or tilt to the setup - none of mine do to any noticeable extent - or be slightly the wrong length (changing infinity focus) a not uncommon issue. However none of these factors lower resolving ability.

Stacking multiple adapters increases the potential errors - in such cases the maximum possible error is the sum of the errors of each adapter, although in real life the errors will usually in part cancel each other out.

There are some adapters with optical elements - most of those designed for Nikon bodies fall into this category (due to Nikon's long rear flange distance) as do the focal reducers such as the metabones. There's a lot more potential for spoiling a lenses performance when adding extra optical elements. Many Nikon adapters have cheap single element lenses which will introduce a host of problems!

 

[Derrel]

I wish I could find Roger Cicala's tests of some high-quality primes using lens adapters...the center resolution figures were usually pretty good, but edges showed significant drops in resolution. How it happens is alignment errors...lenses need to be aligned extreeeeeeeemely precisely to perform well. This was his first article on adapter issues LensRentals.com - There Is No Free Lunch, Episode 763: Lens Adapters

but there was a second test session with extensive comparisons of adapter/no adapter performance. I looked through the older articles, and web searched didn't give me the results I wanted, but basically, the issue is alignment problems. As he points out, the very high-performance Zeiss 35mm f/2 lenses tested showed for example, one side of the image exhibiting serious loss of quality due to the adapter being not aligned perfectly.

And notice that he said his testing showed that lens adapters are not precisely aligned and machine enough for **critical**, valid lens testing on their equipment: " I won't bore you with another 20 graphs that look pretty much like these. We tried Leica to NEX and Leica to Micro 4/3 adapters, Canon to NEX, etc. We tried different lenses on one adapter. It didn't really matter. None of them would be acceptable for testing. Not one.

I'll point out that we carry only name-brand, fairly expensive adapters, not eBay $29 adapters. All of them are tested frequently and used frequently and none of the ones I tested today had any problems. Still, not one of them would be acceptable for testing, so I guess I'm going to have to order those expensive lens mounts after all."

But as he says in this article, video, even 4k video puts low demands on lens performance! So that's a plus for the OP, who wants to adpat some older medium format film-era lenses to a digital camera.

A second way lens adapters can cause resolution issues is the thickness of the sensor stack (aka the protective glass array located right in front of ther sensor). As he shows, m4/3 cameras often have a VERY thick , 4mm thickness, piece of glass in front of the sensor, Canon has about a 2mm thick stack, and old film cameras have of course, no sensor, and use film. The issue here is basically, a miss-matching of the lens to the sensor and the glass stack it has in front of it. The issue here is really not the fault of the adapter, or multiple adapters, but just creating mismatches between a lens and a particular sensor. He has a couple articles on that

LensRentals.com - Sensor Stack Thickness: When Does It Matter?

LensRentals.com - The Glass in the Path: Sensor Stacks and Adapted Lenses

As far as the idea that multiple adapters, and four, or six, or eight mount-to-mount surfaces would create a situation where errors tended to "cancel one another out"...that's not logical in any way at all. At times, errors compound one another. Again, the issue really is one of alignment. And again...some made in China adapter that is supposed to offer infinity focusing, but yet does NOT...means that the machining work is of extremely substandard quality. I don't mean glassless adapters that simply can not and will never achieve infinity focus, like say m42 to Nikon F, but adapters that should easily be able to achieve infinity focus...if an adapter is so poorly machined that the basic thickness of it is improper, then how much confidence would one have that the thing aligns precisely to the camera mount AND to the rear mount on the lens? And there are quite a few adapters that have this problem...

 

[petrochemist]

As your first link says 'Generally, they're acceptable or people wouldn't use them'

In real usage the miss alignments added by an adapter (or for that matter extension tubes) generally make no noticeable difference to the image. It's not a case of miss-aligning a few elements the entire lens is effected, and any tilt or shift is very much smaller than with a tilt/shift lens.

Issues with very short focal lengths are more significant as small changes in the lens sensor distance have a bigger effect on their focus. The only issues I've had with adapting lenses (something I do regularly & rarely for video) have been with a 10mm/2.8 & a 10-17mm fish-eye.

Once optical elements are added (tele converters/ focal reducers / most nikon adapters) alignment becomes more critical. The original 'lens turbo' (a speed booster clone) had severe issues here!