Last test for now, Nikon 50mm f1.8 Series E wide open, which seems to show almost no change in IQ, but with the added light etc (I had to double check that I didn't take two pics from the same shot). If you own older Nikon glass and a m43 camera of any kind, this product is well worth the price I paid (about $50 more than I paid used for the Voigtlander passive adapter used for these tests, and about $50 less than it goes for new). I do not own any f2.8 $1800 zooms or any 1.4G lenses, so I can't test those. If I did, I'd probably not balk at $549+tax locally for the Metabones, anyway. But this focal reducer has made the following lenses more usable on the GH2 and BMPCC: Nikon 50mm f1.4 AIS Nikon 135mm f2.8 pre-AI especially wide open Vivitar 28mm f2.8 making is usable wide open (f2-ish, showed the most improvement overall) I plan to get my hands on a Sigma 10-20 to test (ahead of purchasing) to get as wide as I can on the pocket and I won't hestitate to use it with this adapter, but I will post test shots of that when I can.

The 50mm 1.4 is really the ability to use "1.4" actually f2 with the reducer, where the difference between 1.4 and 2 on the Ais lens make a big difference with the spherical aberration.

But looking at my other results, I'm beginning to suspect that, whatever technology and glass and coating is used to make the RJ Lens Turbo, the simplicity of the design of a focal reducer (in relation to the design of a 135mm or 28mm f2.8 lens) and the advances in Nikon's coating technology between 1971 and 1981 (the two years my 135mm f2.8 and 50mm 1.8 E were 'single-coated') makes it in ways superior to the glass I'm putting in front of it. And since the main issue with my 135 Nikkor-Q and Vivitar MC Wide Angle seem to be aberrations, the coating of the focal reducer appears to be improving the coating-related colour issues more than it is degrading the sharpness, resulting in an overall more usable and pleasing image. That might also explain why the Series E 50mm f1.8 I have, which was 'single-coated' in the early 80s, doesn't exhibit the apparent benefits-the problems don't exist.

Edit: Did a test with the worst lens I have, a Nikon 43-86mm at 86mm wide open (this lens just got more use than it will for the rest of its existence), as your statement, @vicharris , that you haven't seen a test making a lens sharper when used wide open after looking at my two tests showing a subjective sharpness increase using the reducer wide open, insinuates I am, at best, sloppy in my testing. I adjusted the colours to, I hope, show you evidence of my theory (there does appear to be a sharpness hit, but there is clearly an LCA benefit, and in the un-adjusted shot the subjective result is a subjective sharpness increase, making the shot totally unusable instead of complete and utter garbage). But this really is the last test, I'm happy with the reducer, with my lenses, for my purposes. If you have good old nikons that are sharp, but have aberration issues wide open, I think you would be amazed at what the RJ Lens Turbo does to those lenses. If you only plan to use the Sigma 18-35 f1.8 and $2000 f2.8 professional zooms, you'll have to do your own testing.

Full disclosure: I'm just a guy testing a product I paid for, giving an honest opinion. No one is giving me anything for my time, except @vicharris and his skepticism.

Seems to be something like 0.716x, and that's great really.

Anyway taken the Nikon F/G version, cause I have a friend of mine which has Nikon lens :)

With my sigma I can get a super fast 44mm F1.0 lens! But I was looking at some zoom, do you have any suggest? Was thinking at tamron 17-50 F 2.8 to have an F2.0 lens or even a bit faster..

@lonely1

It is rare mount. Can be done, but I am not sure.

@Renovatio, I just got my adapter Nikon G in the mail today and used it on a job. It was great. Nice and snug fit on my Tamron 17-50mm f2.8 on my GH1!!! The extra speed was welcome and it was nice and sharp, since I was able to stop down just a touch and hit the sweet spot of the lens. I'm VERY HAPPY with this buy. Wish there was such a thing possible for my Canon 50D with ML RAW.

@Renovatio, I don't see much of a need for IBIS at these wide angles on the 17-50mm which as you point out is pretty wide on the GH1. I'm probably gonna use a small Steadicam anyway. I don't mind the size of the 17-50mm on the GH1. It's a little big, but not unwieldy. This is an underrated Lens IMO. The Speedbooster really makes it a great tool. It covers most of my needs and I can use it with a future GH4 down the line.

@bobdrenth, the aperture has an extremely short throw. IMO there's no way to accurately make adjustments with it. You have to be very gentle with the adjustment since the entire range is 3/4 of an inch. However it doesn't move in my experience.

The entire RJ adapter is solidly made and fits tightly with no movement or jiggle. There are some notches that you could use as a guide visually but the aperture adjustment is smooth with no stops, which actually is a good thing. I only use the aperture to stop down about 1 stop anyway. I'd use ND for anything more.

The beauty of the Tamron 17-50 is that it's pretty good wide open and just one stop down at 17mm it's as sharp as it can get. Throughout the range of the zoom you're best results are at f4-5.6, so you really get a nice advantage from the RJ speed booster in that it's giving that stop brighter image. So you get a lens that is f2.8-4 when set at f4-5.6, roughly. On my GH1 the lens is excellently good wide angle at 17mm. I'm very happy with this purchase.

I just noticed that the Tamron 17-50mm f2.8 is working very well with the RJ Speed Booster and I didn't even notice that the lens is Parfocal and remains so with the adapter. This is a very good combination for my GH1. I stop down just a touch and this lens is sharp enough for my needs and still bright enough indoors. Still very useable wide open.

If I won't see much improvement with a speed booster on the 35-105 then I'll put that money towards perhaps a more modern brighter (prime) lens.

I am not sure that adapter will make it ultra sharp. Only some of old zooms are sharp.

@oscillian -you're shooting video at 1600 ISO?? I have been told to avoid going over ISO 400 as causes noise and reduces dynamic range? I've never tried it, or risked it as I should say. If it does not impact quality then I guess I could make a lot of use out of that lens. Please can you elaborate further?

If anyone has more of some sample footage, pictures, real life tests, then i'd be happy if you would share links or files..would make my decision easier...this or the 3 times more expensive metabones..[/QUOTE]

@marx92 here's a recent test :

@Qadri

I have the FD 35-105 with RJ Turbo and a G6. I think it's fine for indoor video up to ISO 1600. For stills, not that much.

I have that lens and a G6 as well. To be honest, I heard great things about this zoom when I bought it, but I've never really been all that impressed with it in practice. Its a super versatile range, and it looks really professional on a tiny camera body, but I wouldn't buy another one if anything happens to this one. If only I could afford that lumix zoom at f/2.8... I thought maybe a lens turbo would make it more attractive, gaining a stop of light and everything, but from what I've seen so far (just picked one up myself), I'm still not loving it. :/

@dishe,

That recent test you posted looks pretty good. I thought you would see the blue spot in a few of those very bright shots but nothing!

Has the blue spot issue largely been fixed now?

On the Blackmagic Pocket, my copy of the RJ Lens Turbo fits the mount but has a too tight fit to be clicked/screwed in; on the GH2, it's very tight but can still be screwed/clicked in and out with some use of force; on the GH1, it's an easy fit. Since this is my second copy of the RJ which shows these issues, they seem to be systematic rather than coincidental.

Have other people experienced the same problems? Is there an easy fix (aside from returning the adapter)?