Blackmagic Forum

I've tried twice to post this question but am having trouble with this forum apparently.

I'm looking into B4 adapters that are not as pricey as the MTF Services one, does anyone have a recommendation?

http://www.ebay.com/sch/i.html?_odkw=B4 ... r&_sacat=0



though with adapters you very much get what you pay for. A few hundreths of an inch off and your lenses won't focus right-- especially on the wide end.

I take it you don't have any experience with these cheaper adapters?

I do have an adapter on a 2/3" Canon zoom; but it came with the b/4 put on it, so I don't know who made it. I do know that the lens is pretty un-usable on the wide end due to the low cost adapter as it's off by a bit so none of the marks line up and you have no infinity focus. this goes away by about 20mm on the lens-- of course with an adapter you're now not only a stop of two loss of light, but also shooting at a 40mm lens which is a bit long on a S16mm sensor.

There are lots of issues using a B4 lens on the BMCC.
Crop factor is one:
Cheap adapters can let you down with flange distance inaccuracy.
There is the notion that B4's are made for triple CCD sensors and focus the 3 component colours, RG&B at different depths to counter registration errors due to the dichroic mirrors.
I believe that the small sensor and long flange distance of the 2/3" necessitated chromatic aberration compensation by splitting the difference between red & blue and focusing at the green (middle)wavelength to offset the CA.
There is a very expensive ($5000) adapter reputed to offset CA optically.
As for reducing F stops, many B4's are very fast to start with and can cope with 1 or 2 stops loss.

Info here could help though it is for B4 - M43's:
https://www.facebook.com/groups/B4onM43/

I have ordered a B4-M43 adapter from a Polish guy who sells on ebay and also from his own site:
http://en.foto-akcesoria.com.pl/index.php/kategoria/35/canon-eos-adapters
I'm planning on trying my B4 on the Pocket Cam when I get it.

I thought of buying one of the Polish adapters as well as a 1.4 teleconverter for use on the 4K when I get mine but the use of B4's on large sensors does not work so well I believe..

They do better on smaller sensors.
Many are using them on GH2's etc.

There is a rumour that Metabones is working on an adapter.
A B4-M43 Speedbooster would be a dream.

I bought one of the B4 adaptors from Poland and it seems to be pretty well made, operates smoothly and is a nice snug fit both to the BMPCC and all the lenses I've tested it with.



I've posted a few more frame-grabs to the B4onM43 facebook group, and hope to publish a fuller report when I have time.

Hi Martin.
I can't wait to get my pocket.

I haven't personally noticed too much CA using B4s on the GH2 previously, and I pulled out the zoom on the short as well.
The biggest issue is the physical dimensions of the mount and the doubler. If you can live with that, depending on the type of shooting you do, it can be a nice solution. Especially if you can power up the servos in them.

I will say that if any of your lens adapters have little machine screws on them; watch out-- they will wiggle out and throw things a miss.

zenvideo wrote:I bought one of the B4 adaptors from Poland and it seems to be pretty well made, operates smoothly and is a nice snug fit both to the BMPCC and all the lenses I've tested it with.



I've posted a few more frame-grabs to the B4onM43 facebook group, and hope to publish a fuller report when I have time.

I've now had time to upload some tables containing frame-grabs from my tests to assess vignetting and focus at different focal lengths and apertures (F4, F2.8 and wide open), with and without using a doubler (where the lens has one). Hope they provide some useful pointers as to what to expect from B4 lenses on a camera like the BMPCC, although to be fair most of these were old lenses and none were current generation HD lenses.

Test results can be seen at: http://www.zenvideo.co.uk/b4_on_mft_on_bmpcc.htm