Lens: Fujinon A12x10BRM-88 (B4 mount)

Posted on 25 May 2012

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For quick ENG-style shooting I wanted a real ENG lens on my GH2 camera. I’ve picked up this Fujinon A12x10BRM-88 (model VCL-1012BY) B4 mount lens for about $ 150 to test if it would work. This is a very old 1:1.7/10-120mm lens with rotating focus (no internal focus), so if it works well I will replace it with a wider internal focus lens.

There are a lot of secondhand SD (standard definition) video-lenses on the market, some of them are really useful with the GH2. The biggest advantage of those lenses is that you will have constant aperture, stopless iris, internal zoom & focus (the front element will not rotate or move in/out) and powered zoom.

Does it work?

Rumors of “being built for three chip CCD’s and thus unusable for single CCD” are untrue. Three chip or not, all ENG lenses have same chromatic focal point, thus will focus all colors in the same plane. Back-focus needs to be adjusted though.” (Grunf). On the other hand, there is this user on DVXuser that sells all of his gear because of CA problems, he says one needs the $ 5000 adapter to get rid of the CA problems.

I’ve tried and am not satisfied yet. I found that my lens has a white glow around the highlights, which is known as coma. Is it bad? I don’t know, you can use it as a style like in eat pray love. This might be because it is a pre-CMOS design. It might lack the rear-element multicoating of more modern lenses, which is a substantial factor in reducing the additional flare caused by digital sensors. I’ve tried putting a mask with a round hole of 11 mm in front of the sensor to reduce reflections but this doesn’t help. It seems like te only remedy is to keep the aperture at f/4 or higher.

Other options

So I’ve been reading a bit about the experiences of other GH2 users. To summarize, there are two main brands: Canon and Fujinon.

Canon lenses that begin with a J means they are made for 2/3″ B4 camera’s. If there is a B in the name, it means there is a B prism adjustment built-in. As far as I understand, the IRS addition means it has internal focus. Some say one should buy a Canon J13x9B IRS, Canon J14ax8.5B IRS or Canon J8x6B IRS, while others say you should buy one without B-prism adjust feature, as it could make the chromatic aberration go bad.

Fujinon lenses have another naming system, which I didn’t figure out yet. The general advise is to get a Pegasus III A14x8.5BERM or Fujinon Pegasus I/II A14x9BERM.

I have tested a few:

  • Angenieeux T15x8.3 AIF. Extender, Internal focus.
  • Canon IF+ J9Ax5.2B4. Extender, Internal focus.

Both of them have the coma problem as well. Grunf suggests to have another look at the adapter, as it might be reflections from the adapter. To be continued.

B4 mount

The B4 (or 2/3″ Bayonet Sony) mount is the standard mount for all 2/3″ 3 CCD professional broadcast camera’s, both SD and HD. To get it to work on the DSLR, you’ll need an adapter.

Sensor size

First off, you’ll need to know that these lenses are only covering the 2/3″ area with an image circle diameter of 11 mm. You’ll need to enlarge this image to get it working on a 4/3″ camera (22 mm image circle). See this picture for the difference between GH2 and the other m43 camera’s.

One way to do that is finding a lens with a 2x extender. The best way to do it is using  a full-frame converter like the Canon FD one instead of the built in B4-lens tele-converter, which wasn’t originally designed to cover a large sensor.

Both of those options will have you loose one or two stops of light. You can solve this by using the GH2’s ETC mode, but this has other disadvantages:

  • it will give you a tighter angle of view (it’s 2,6x zoom in 1080 mode). This should result in an actual sensor area of about 8×4,5 mm.
  • there will be more noise, you might not want to go above 400 ISO
  • with firmware 1.1 you’ll loose the external HDMI output, so no external viewfinder

HDMI out

For focussing it would be nice to have HDMI out while in ETC mode. See this post about my quest for it. There is one other guy stating that he did get it to work once.

Unfortunately, both RalphB and Vitaliy say that the patch never worked. They know, so I guess it’s end of story. One thing to try is the composite out, which can be enabled by holding the trash-button for 10 seconds.

Adapters

These are the possible adapters that I found:

  • It might be best to try to find a B4 to Canon FD mount adapter with a $ 8 FD tele-converter. There is no m4/3 tele-converter on the market. This bumkicho took pre-orders back in 2010.
  • $ 120 jinfinance b4 to micro 4/3 adapter. the notch is not at the top where it’s supposed to be so your handgrip will be at the bottom of the lens instead of the right side.
  • $ 330 Polish adapter (Ciecio on ebay). Does have baseplate support, like the other adapters on their website. Backfocus can be adjusted. I bought one with some scratches from their store, for E 180 only (25/3/12).
  • £ 295 MTF services B4 to M4/3 adapter. Provision to accept the £ 75 MTF support bridge for support bars.
  • £ 950 MTF services B4 to EF adapter. Built in optics (multi-layer coated), but still need B4 lenses with built in 2x extender. Complete with support bridge.
  • $4800 Abelcine B4/MFT adapter. This is optical, so with light loss (2 stops?) and full coverage of the sensor. Also, fix for different spectral alignments.

Another option would have been to use a B4 to EOS adapter together with a $ 103  Canon 2x tele-converter. Then use $ 13 EOS to M4/3 mount (see Canon). I didn’t think this would work as it the B4 to EOS adapter is a replacement, not a mount adapter. Turbodog tried it and proved that I was right about this.

Ciecio adapter

This is a great adapter. The baseplate support is made for the same height as the AF-100:

IMG_0491

But for the GH2 it would be great to use this support to mount it to the rig, without supporting the camera (fast access to battery!). Unfortunately, the two holes are too close together:

IMG_0543

So I would need to make a custom 15mm rod support for this adapter. The advantage would be that I could make it so that it would bring the lens’ center to the 85mm standard height at the same time.

Controls

Most of these lenses are equipped with a nice handgrip, with start/stop and zoom buttons on it. Most of them use a 12 pin Hirose plug. But be aware, there are also different 12 pin Hirose CCTV plugs on the market, as well as 6-pin Hirose lenses.

You can power them with $ 60 D-tap or DC12v to 12 Pin Hirose. Here is more information about the pin-layout of the Hirose plug (be aware: there are 12, 8 and 6 pin layouts as well as twist-on and push-on plugs). It would be nice to use the REC button as shutter remote control as it seems like this is possible. And if you are really good you might even get the iris to work with the camera through the electronics in the lens-mount.

Afterthought

So far, I didn’t miss the motor zoom. But I do miss the HDMI output. So I would like to replace this lens with a M4/3 equivalent: it would be nice to have AF and HDMI out if needed. What would I need: a 25-300 mm zoomlens with internal zoom, so I could use it with my mattebox. I would like it to have AF (for photography and steadicam work) but also manual focus, with at least a 90 degrees throw from 1m to infinity. I’ve tested lenses with a shorter focus throw but that really doesn’t work.

To get the same nice depth of field I’m used to with my f/1.7 ENG lens, it would need to be f/4 at least. Because it’s for video this has to be a constant f/number of  f/4 across the whole zoom range. Then, due to the f/4, for most run&gun situations I would have to use more gain instead, so my max. ISO goes up from 400 to about 1000 ISO. I would have to test which is better: ETC f/1.7 at ISO 160 or M4/3 f/4 at ISO 400 (for well-lit situations), but also test it at ISO 400 versus ISO 1000 (run and gun).

And to add to my wishlist: If I want a really short depth of field (like with the nice Canon EF 70-200mm f/2.8L IS II USM on a Canon 7D) It would be nice to have a 55-160mm f/2 lens. Or to compare to a fullframe camera it would be great to have it to be f/1.4.

So I’ve been looking around but as far as I could see I would have to get me about $ 10.000 and buy at least 3 lenses:

Or I should buy a superzoom camera like the $ 500 Panasonic DMC-FZ200 with it’s fixed 12-300 mm f/2.8 equivalent lens? No, first of all it is not an internal zoom. Second: this is a 4.5-108 mm lens on a 1/2.3″ sensor (5.5 crop factor). In video mode it’s even worse with it’s 6.17 mm sensor width (compared to the 8 mm of my ETC mode). This means that it’s f/2.8 only gives a depth of field is comparable to a f/8 on my m4/3 camera. So no: I should not buy a superzoom.

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Posted in: GH2, Lenses