Some test: NEX 7 + turbo VS A99 : Introduction

[InTheSky]

Well, processing the picture, I found that the 50mm 1.2 MD lens that I use are not really the same . One rokkor-X and other MD. So probably David Will be able to help me to decide wish one should be the best.

Man ... this take time to collect all the data and put that on pbase ... . If I got time (what I already don't have), I will try to switch the back end of each lens and redo the same test tomorrow ... , That will be at the same time a test for the MD and the Rokkor-X ...

So for the moment, here is the plan for the next weeks: I will address some lens on the NEX-7 and the A99 using the cheap Turbo adapter that you can find on eBay to use directly without any modification you old MD lens on you NEX-7 and simulate that you are on Full 35mm sensor.

The challenge lenses :

A99 VS NEX 7
100mm 2.0 Minolta Alpha VS Metabone Speedbooster + Canon 100 2.0 EF
135mm Zeiss 1.8 Alpha VS Turbo MD + 135mm 2.0 MD
58mm 1.2 MD Modified to Alpha VS Turbo MD + 58mm 1.2 MD
50mm 1.2 MD modified to Alpha VS Turbo MD 1.2 MD



view of each camera :



other side of view :



Frank

[pakodominguez]

I think a good test is the same lens, on the NEX, with the Speed Booster and with a plain adapter and see if htere is z difference in sharpness and contrast.
Thanks Frank for your efforts

Pako

[David Kilpatrick]

Hate to say this, but using an f/1.2 on the reducing converter takes you past the zero point - it can't actually yield the f/0.9 or whatever would be (no time to calculate now). The turbo converters work up to f/1.4 but even then, at reduced efficiency - their effect will be most accurate with lenses of f/2 or smaller aperture, and obviously very beneficial with lenses such as the very high resolution 50mm f/2 late Rokkor MC (SRT 100X standard lens).

So I wouldn't be concerned with whether a Rokkor-X or MD Rokkor 50mm f/1.2 was better; sample variation even with such a high grade lens would be more than any design difference. I would experiment with a range of standards, 50mm f/1.7, 50mm f/1.4, 50mm f/2, 45mm f/2, even some of the classic 'old glass' lenses - 58mm f/1.4, 55mm f/1.4 and so on.

If I had more useful old MD lenses I'd try one of these converters, but of course what we really need is an Auto and even AF equipped version for A-mount lenses. I'd love to see what my 24mm f/2 did with AF and a 0.7X format reducer - 16mm f/1.4 and probably a fully usable f/1.4 as well.

David

[pakodominguez]

If I had more useful old MD lenses I'd try one of these converters, but of course what we really need is an Auto and even AF equipped version for A-mount lenses. I'd love to see what my 24mm f/2 did with AF and a 0.7X format reducer - 16mm f/1.4 and probably a fully usable f/1.4 as well.

David

I haven't see yet any "Turbo" adapter for A mount. I'm waiting for the adapter for MC/MD mount I bought a couple of days ago for doing my own test -I'm interested on seen how the MD 24mm f2.8, the 50 Macro f3.5 or the MC 58 f1.4 performs with the adapter...
Regards

Pako

[InTheSky]

Thanks David, You are right. I have stop my effort to post all the test picture. I finally swap the back of each lens and do some test. The new Rokkor seems a little bit better on the A99, but not a huge change. And on the adapter turbo, a little less flare problem, but still very strange effect at F1.2, and almost gone at 2.0.

I remember one of my friend sharing me a 58mm 1.2 modified for Canon that I tried on the Metabone and the result was very better. Probably the next step will be to tried to modified them for the metabone, that is very better optically.

http://www.pbase.com/nadeauf/metabonesuper

But the turbo adapter is good for video at F1.2 for those who are searching for better low light, but don't expect high contrast if you get direct light in the lens. The Very Bad Problem of this adapter is Flare. Once you tried to take a picture of 'classic' sunset, you get horrible ghost in the lens (that is not there with the Metabone).



I have tamron 24mm f2.5 with MD adapter still left in my inventory of old lens, I will do some test later.

Now this week, it is the time to sell all my A-Mount lenses and the A99. I only keeping the NEX-7 and NEX-5 for the moment and running with thoses adapter with old lenses If I want the "full frame" feeling.

Frank

[David Kilpatrick]

I have ordered an MD fit Chinese Zhangyou (?) model, which I can try with: 24mm f/2.8 Sigma, 28mm f/2.8 Rokkor MD, 50mm f/1.7 Rokkor MC, 200mm f/4.5 Rokkor MC, 50mm f/4 Pentax SMC Macro, 50mm f/1.4 Super Takumar, 200mm f/3 Vivitar Series 1, 30mm Meyer Lydith, 135mm f/2.8 Hanimex, 58mm f/2 Jupiter, and maybe a couple of others.

David

[Vidgamer]

Frank, the quality is good enough for you, it sounds like. Are you seeing much degradation from the "lens turbo"?

I've been reading (and watching a podcast) from Trey Ratcliff who had a similar conversion. http://www.stuckincustoms.com/

David, about f-stops <1.2, I think DxO has an article on the diminishing returns from lenses with apertures wider than even f1.8. I guess it has to do with the angle of light from the rear element, but manufacturers apparently are spoofing the ISO so the user gets the values reported as expected, but f1.2 isn't really giving you f1.2. This is for the DSLRs, not just the Nex. I assume that the problem is less for FF sensors, though.

[David Kilpatrick]

I've been writing about sensor mapping for several years - since the era of the Minolta Dimage A2, which is when I learned about this directly from the Japanese techs. Sensor mapping is used to correct for many things including ex-factory pixel level calibration, but also to compensate for 'typical' lenses of different apertures. On most cameras it is not lens specific so you get the same 'map' for a 200mm f/2 as you do for a 24mm f/2; on most cameras, it runs out at f/1.0 or even at f/1.4 because it was never planned to have any faster lens.

The NEX can not apply any mapping to turbo-converted ultra fast apertures wider than f/1.4, as it reverts to reporting and using f/1.0 mapping. It also will not map shading correctly on smaller prime lenses added to the turbo converters. There's no information reaching the camera CPU to pick the mapping level. This, and the way that microlenses on sensors aperture-limit the incoming ray bundle, make it pointless to use anything faster than f/1.4 on a turbo 0.7X converter, except for aesthetic reasons (bokeh).

David

[InTheSky]

David, I think you will find the same feeling like me that the old MD lenses even if they are not perfect on the cheap Full frame simulator, they are still fun to use with the size and good construction they where.

So far I found the perfect setting for the NEX 7 with those old lenses. You put your camera in Speed priority. Because the lenses if not connected to the camera, you can Create what is not available in Manual mode on the NEX and even on the A99. You have now a single setup that can switch from Video and Photo with perfect control and also with the ability to put priority on the aperture also and let the camera adjust alone the ISO, and you can quickly correct the EV with the other wheel.

I found annoying with Sony that in video mode, even if you are in 24p, the camera always want to shutter at 1/50s minimum, this keep you a good one stop of light that make the difference in a Noisy or not movie.

Instead you want to make a poster of your picture, I still recommend the adapter at F1.2 in movie and also for "web" and 4x6 printing album . I like to take picture when I almost don't have to move the slider in Lightroom to get my effect, I have also put a custom hood on the lens that capture some more flare and eat some more light in the corner to create vignetting.







Regards,

Frank

P.S. My A99 in on Ebay and the rest of my Alpha mount lenses (the 400mm 4.5 is gone since yesterday) , this is the end of big camera body for day to day picture ... , I will rent Canon lenses on my NEX 7 with the metabone If I need to do some contract in the future.

[pakodominguez]

I found this review of the Metabones Speedbooster adapter (for M4/3...)
http://www.slrlounge.com/near-full-fram ... ter-review
The author touch some interesting topics. I'm specially concerned about the quality at the corners on APS-C, apparently closing the aperture 2 stops helps a lot.
I'm still waiting for the Chinese speedboster I order few weeks ago, I guess it is a bout to arrive...

[David Kilpatrick]

Not much wrong with the Chines Zhongyi I've got (identical to Mitakon) though of course it depends on the lens used. I do not have a 17mm f/4 or 20mm f/2.8 to try, those would be just ideal. The problem for MFT is that you really need a 0.5X converter and this is not practical.

I can confirm that the converters for NEX includ a four-element lens group with a power just over 10 dioptres and an aperture equal at 110mm focal length (for the lens group) to around f4. The adaptor can, if mounted using various rings, be used on a bellows and acts as a 110mm f/4 super soft focus portrait lens. Aberrations are glowing and colourful. This unintended use is one I will leave to someone more creative than me to write up, or maybe I should just do a page about this stuff.

David