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11-07-2014, 04:54 PM   #1
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Pentax K to NEX "speed booster" adapter

I've seen past threads on the forum about this particular kind of adapter but there wasn't a clear answer or opinion on them one way or the other.

Here is the exact item:

http://www.ebay.com/itm/like/400488751824?lpid=82

I have a cheaper NEX camera to experiment with and having close to full-frame focal length available from a nice FF K mount lens would be very welcome.

The general off-hand opinion is that any glass in an adapter must be poor quality. That's not necessarily so, but its the major concern of course.

I'm interested in using the Sigma 70mm macro on the NEX to get a close to FF focal length - and more light on the sensor. If I buy one or two lenses I'll never be able to afford a real FF camera - unless the prices fall significantly. But the adapter is available and will put an idle camera to use and offer another view through a nice lens. Its a win/win situation, and even if the adapter glass is not the best, it will still allow for photos.

Can anyone offer any images and/or experiences?

Thank you!
K

11-07-2014, 05:26 PM   #2
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QuoteOriginally posted by krema Quote
The general off-hand opinion is that any glass in an adapter must be poor quality. That's not necessarily so, but its the major concern of course.
I don't think anyone has the opinion that the "glass in an adapter must be poor quality." The fact is any glass in an adapter (or lens filter) will reduce aspects of image quality, such as sharpness and glare, to a degree.

If you Google, you'll find a number of people have posted about their experiences with the Roxsen.
11-07-2014, 05:40 PM   #3
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QuoteOriginally posted by krema Quote
I've seen past threads on the forum about this particular kind of adapter but there wasn't a clear answer or opinion on them one way or the other.
I think the opinion has been that the better ones work very nicely if you are shooting a NEX and don't work at all if you are shooting Pentax.


Steve
11-07-2014, 05:48 PM   #4
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A focal reducer tends to reduce lens imperfection characteristics such as chromatic aberration. They seem awesome really as another tool/toy to play with on mirrorless cameras.

11-07-2014, 05:58 PM   #5
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QuoteOriginally posted by luftfluss Quote
I don't think anyone has the opinion that the "glass in an adapter must be poor quality." The fact is any glass in an adapter (or lens filter) will reduce aspects of image quality, such as sharpness and glare, to a degree.

If you Google, you'll find a number of people have posted about their experiences with the Roxsen.
I should have qualified my comment about glass with "Chinese-made" glass in lower-priced adapters, and as for poor, that wasn't the best descriptor either, though I haven't read an opinion of adapters (particularly the simple lens adapters that require glass, such as EF to K, Nikon to K, etc.) that mentioned actually liking the effect produced by the adapter's glass.

Of course I already spent hours searching up videos and pseudo-reviews. It seemed that many were more concerned with the OOF effect of even thinner DOF than the overall quality of the glass. From the photos posted I couldn't see any visible degradation, but some updated commentary from forum users here would be much preferable to me.

---------- Post added 8th Nov 2014 at 01:03 ----------

QuoteOriginally posted by stevebrot Quote
I think the opinion has been that the better ones work very nicely if you are shooting a NEX and don't work at all if you are shooting Pentax.

Steve
Better being the operative word. Is this one (in the link above) of the "better" ones, or its higher-priced, engraved sibling, "Zhong Yi?!"

Zhong Yi Focal Reducer Speed Booster II Lens Turbo Adapter Pentax K to Sony NEX

---------- Post added 8th Nov 2014 at 01:09 ----------

QuoteOriginally posted by richandfleur Quote
A focal reducer tends to reduce lens imperfection characteristics such as chromatic aberration. They seem awesome really as another tool/toy to play with on mirrorless cameras.
Thanks for your input. I'm hoping it can lean more towards the tool side than toy, but I understand your meaning.

I'm a little cautious because I own a few unwanted wide-angle adapter that produced a lot of distortion regardless of the lens used. Maybe this reduction lens is a different design than a wide-angle adapter. I've read about photocopier and other reducing lenses being sharp, so it must be a tried and true technique.

Thank you.
11-07-2014, 07:04 PM   #6
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QuoteOriginally posted by krema Quote
I should have qualified my comment about glass with "Chinese-made" glass in lower-priced adapters, and as for poor, that wasn't the best descriptor either, though I haven't read an opinion of adapters (particularly the simple lens adapters that require glass, such as EF to K, Nikon to K, etc.) that mentioned actually liking the effect produced by the adapter's glass.

Of course I already spent hours searching up videos and pseudo-reviews. It seemed that many were more concerned with the OOF effect of even thinner DOF than the overall quality of the glass. From the photos posted I couldn't see any visible degradation, but some updated commentary from forum users here would be much preferable to me.

---------- Post added 8th Nov 2014 at 01:03 ----------



Better being the operative word. Is this one (in the link above) of the "better" ones, or its higher-priced, engraved sibling, "Zhong Yi?!"

Zhong Yi Focal Reducer Speed Booster II Lens Turbo Adapter Pentax K to Sony NEX

---------- Post added 8th Nov 2014 at 01:09 ----------



Thanks for your input. I'm hoping it can lean more towards the tool side than toy, but I understand your meaning.

I'm a little cautious because I own a few unwanted wide-angle adapter that produced a lot of distortion regardless of the lens used. Maybe this reduction lens is a different design than a wide-angle adapter. I've read about photocopier and other reducing lenses being sharp, so it must be a tried and true technique.

Thank you.
Zhong yi works well and the only downfall i have had is when shooting in some rare lighting conditions you get a big violet aperture image. Mine is their first model and the problem may be fixed by now.
11-07-2014, 09:14 PM   #7
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I wrote this a while back about the "Lens Turbo":

https://www.pentaxforums.com/forums/76-non-pentax-cameras-canon-nikon-etc/228...ens-turbo.html
11-07-2014, 09:36 PM   #8
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QuoteOriginally posted by krema Quote
I'm a little cautious because I own a few unwanted wide-angle adapter that produced a lot of distortion regardless of the lens used. Maybe this reduction lens is a different design than a wide-angle adapter. I've read about photocopier and other reducing lenses being sharp, so it must be a tried and true technique.
Yes, those wide-angle adapters have a completely different design than a Speed-Booster adapter. I think some of the wide-angle adapters work well with small-sensored cameras, but obviously you are looking for quality.

11-07-2014, 11:04 PM   #9
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Check out the metabones white paper on this concept. Seriously, it shouldn't be considered like a teleconverter which typically has shortfalls of increasing purple fringing etc and reducing the minimum aperture setting. The focal reducer is actually the opposite, using all the light a FF lens captures and focusing it down onto the smaller APS-C sensor.


http://www.metabones.com/assets/a/stories/Speed%20Booster%20White%20Paper.pdf
11-08-2014, 11:23 AM   #10
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QuoteOriginally posted by richandfleur Quote
Check out the metabones white paper on this concept. Seriously, it shouldn't be considered like a teleconverter which typically has shortfalls of increasing purple fringing etc and reducing the minimum aperture setting. The focal reducer is actually the opposite, using all the light a FF lens captures and focusing it down onto the smaller APS-C sensor.


http://www.metabones.com/assets/a/stories/Speed%20Booster%20White%20Paper.pdf
Thanks for your comment.

It was the Metabones (specifically) and Lens Turbo (with cautions) products that was thinking of when I referred to higher quality adapters. There is some confusion regarding what these adapters do and whether they degrade quality. My understanding, from the outside looking in (not a mirrorless shooter) is:
  • These are special purpose and not general purpose adapters
  • The concept is sound and high quality is possible
  • Quality results are dependent on the quality of the optics and the adapter alignment. As with inexpensive tele-converters, if you buy cheap, you will get cheap.
  • Similar devices are not possible for cropped format SLRs


Steve

Last edited by stevebrot; 11-08-2014 at 11:35 AM.
11-08-2014, 11:56 AM   #11
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Here is a link with some samples on my nex 5n
https://www.pentaxforums.com/forums/76-non-pentax-cameras-canon-nikon-etc/226...gear-porn.html
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