NEX -- Why only 2 e-mount lenses?

[David Kilpatrick]

Anyway, the 16mm is a very good lens. It beats the weak 17mm or 20mm on microfourthirds any day. Here's a sample...

16mmlens-geometry-sharpness.jpg (393.65 KiB) Viewed 4756 times

the only decent sunshine we got - at breakfast time, before handing the gear back! The day we went out with the kit on a trip to shoot was rubbish, horrible flat light.

David

[alphaomega]

David Kilpatrick wrote:

Yes, a rear 1.4X converter would be interesting - 22.4mm f/4. The central zone of the 16mm is exceptionally sharp and would probably take enlargement. Of more potential interest, and possible because of the short back focus distance, would be a rear X0.66 converter as used for film/video cameras to reduce 35mm lenses to work on 16mm.

Such a converter would take full-frame Alpha lenses, and reduce the field to APS-C, while increasing the maximum aperture (the reverse of a tele converter). The 50mm f/1.4 would become a remarkable 30mm f/1 lens for the NEX. My guess is that if they did this, the contrast-detect AF would cease to be a problem. Imagine the 70-200mm SSM - it would become a 46-132mm f/2. Even a standard kit lens like the 24-105mm f/3.5-4.5 would become a 16-70mm f/2.6-3.2.

Now there is a great idea. I wonder if Sony or and independent would take up this possibility. Presumably there would be manual focus only but perhaps auto exposure. I wonder if David has any information on to what extent such a X0.66 converter would reduce sharpness/definition and possibly produce distortions and maybe increase CA. On the longer lenses we would still have the problem of no SSS either in body or lens. If the NEX7 has SSS built in as rumoured this problem could be eliminated.

[David Kilpatrick]

Converters like this increase resolution, improving definition by compressing the performance of the lens from full frame down to APS-C. The Zeiss converters made for Arriflex achieve 400 line pairs per millimetre when teamed with Zeiss cine lenses. Also, AF can be implemented in the converter. Because of its relatively strong effect, moving the converter group or an element within the converter can provide AF even with manual lenses. The same principle was used by the early AF tele converter for MD lenses, which was made briefly for the M-AF system, but the range of focusing is limited with a tele converter.

A 0.66X rear lens converter for NEX could adapt many types of lens, from MD to M42, Nikon F, you name it - it could reduce their image to APS-C, add one stop to their aperture, boost resolution by maybe 30-40% compared to the naked lens, and provide a reasonable AF function provided the master lens was set to a suitable aperture (I would guess f/8 or wider on the prime lens).

David

[alphaomega]

So maybe there is a real business opportunity for someone such as Novoflex to design a X0.66 adapter to link Alpha mount lenses to the NEX line and provide both AF and AE in the process (if Sony are not grabbing the oportunity first). Novoflex currently provide medium format lenses to Alpha mount adapters but not sure if they have any competence in providing reduced image reduction converters such as an X0.66 device. With the NEX7 there may even be SSS in the body. This could be a real boon for W/A enthusiasts such as me (if I ever purchased an EVIL that is). I just feel that with an adapter added in and Alpha lenses there is nothing gained in size and weight over fitting the lens directly to an Alpha camera. My Panasonic LX2/3 provide such good image quality using RAW combined with light weight and small size that there is no real room between these and an A350 or A550. With the advent of PS C5 and ACR6 it will be possible to get higher ISO quality images from these P&S jewels (maybe two stops).

[alphaomega]

I have a conceptual problem with David Kilpatrick's statement

Such a converter would take full-frame Alpha lenses, and reduce the field to APS-C, while increasing the maximum aperture (the reverse of a tele converter). The 50mm f/1.4 would become a remarkable 30mm f/1 lens for the NEX. My guess is that if they did this, the contrast-detect AF would cease to be a problem. Imagine the 70-200mm SSM - it would become a 46-132mm f/2. Even a standard kit lens like the 24-105mm f/3.5-4.5 would become a 16-70mm f/2.6-3.2.

Here is my problem. If I fit a FF 70-200mm zoom to my APS-C DSLR it turns itself into a 105-300mm zoom. If I then fit a (so far fictitious) X0.66 converter, the FF 70-200mm zoom returns to being a 70-200mm on the APS-C camera rather than the suggested 46-132mm. Where am I going wrong in my thinking?

[Dr. Harout]

Here is my problem. If I fit a FF 70-200mm zoom to my APS-C DSLR it turns itself into a 105-300mm zoom. If I then fit a (so far fictitious) X0.66 converter, the FF 70-200mm zoom returns to being a 70-200mm on the APS-C camera rather than the suggested 46-132mm. Where am I going wrong in my thinking?

Simple miscalculation I guess.
Fitting a FF 70-200 on a APS-C would not change the focal length, just the field of vision. It means you still have 70-200 on APS-C focal length wise, but yet having 105-300mm field of vision wise.
Whenever using a converter you are shifting the focal length not just the field of vision.

[Greg Beetham]

I think you would still have to apply the 1.5 APS-C multiplier to the 'result' of adding a negative extender, ie. 1.5 X 70-200 = 105-300 then 105-300 X .66 = 69.3-198.
Greg

[David Kilpatrick]

Er no, focal lengths don't change with 1.5X sensor factors but they do change with converters. The figures I gave are correct. The 0.66X converter would restore the 'effective' focal length relative to 35mm full frame, but to do so, it changes the absolute (actual) focal length.

Do not be confused by some consumer cameras which mark lenses that are actually 7.2-50.6mm as 28-200mm

David

[Greg Beetham]

Ah I think I get it, the NEX .66 converter is not just shortening the focal length, it's converting the FF image circle to APS-C image circle as well.
Greg

[alphaomega]

Thanks for the clarifications. I think I have got it now.
The FF 70-200mm becomes a 105-300 as field of view only in APS-C.
The X0.66 converter makes the field of view in APS-C into 70-200 but the actual focal length is changed to 46-132mm. This would also change the field of view to 46-132 if this 70-200 was fitted to a FF camera with a hypothetical X0.66 converter.
I hope I am right now.

[David Kilpatrick]

Right, except that it's impossible to make rear of lens 0.66X converters for full frame, as the optics have to go where the mirror is. The NEX would allow this. For full frame, such converters always go on the front of the lens. I have a good Soligor 0.75X front converter. Also, front converters do not change the lens aperture either way.

David

[youpii]

Why didn't they announce an adapter for Vectis lenses?

[peterottaway]

The Vectis was not exactly a runaway success so it probably is not worth the effort. Also such an adapter would only compound the problem for Sony of most of us buying second hand Minolta lenses.

[youpii]

The Vectis was not exactly a runaway success so it probably is not worth the effort. Also such an adapter would only compound the problem for Sony of most of us buying second hand Minolta lenses.

Sony is not flooding the market with Sony lenses either... I think most of us buy Minolta lenses (sometimes for more than the brand new price of a Canon equivalent) when there is no Sony alternative.
Somehow, I feel that Sony still has the electronics culture and tend to focus on camera bodies.

[peterottaway]

Sony is not flooding the market with Sony lenses either... I think most of us buy Minolta lenses (sometimes for more than the brand new price of a Canon equivalent) there is no Sony alternative.Somehow, I feel that Sony still has the electronics culture and tend to focus on camera bodies.

I very much agree that it looks like Sony has found it easier to set up the camera manufacturing side of the business with their experience in electronics and consumer goods. The craft of producing high quality optics in anything like the range and quantity we wish for is just a lot of hard, frustrating work.

Also personally I plead not guilty to paying more for old than for new. My rule of thumb is even NIB old stock Minolta glass,once it reaches about 2/3 of new price Sony or Nikon I pause and usually pass.

Which is why I'm so busy scanning sites for hints that some of my dreams may come true because it is not just Sony that hasn't been delivering.