Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here.

---

Focal reducer/Speed booster adapter

for/Pentax PK K bayonet lens to Sony NEX mount 5 6 7 camera FS700 FS100

All metal structure, with excellent opticals (4 elements/2 groups, super multi-coated)
what it does:

•
reduce the focal length (by 0.72x wider)

•
Ex. 50mm lens on NEX with the adpater, eff. focal length is 50mm x 1.5(crop) x 0.72 = 54mm

　
•
effectively increases the maximum aperture of the lens by 1 stop



•
(in other words, under the same aperture, you can use faster shutter speed (by 1 stop).

　 what it does not:
there is no electronic integration, no auto fucusing

(you still need to manually focus your lens and aperture, etc.)

Focal Reducer Speed Booster Adapter Pentax PK K to Sony NEX 3 5 6 7 FS700 FS100 | eBay

[HSV]

Thanks to y'all for the info...I'll be ordering one of these tonight.

Cheers!

[devorama]

This thing is a ton of fun. It's great to use with my Pentax 50mm F/1.2 and Rokinon 85mm F/1.4 lens. It really gives that shallow DoF you expect from a full frame camera.

[rawr]

It really gives that shallow DoF you expect from a full frame camera.

I forgot your flickr. Any pix using the BowSamRokViv 85 f1.4?

[devorama]

I forgot your flickr. Any pix using the BowSamRokViv 85 f1.4?

Here's a quick shot I took with the Lens Turbo and Rokinon 85mm at F/1.4

[rawr]

Here's a quick shot I took with the Lens Turbo and Rokinon 85mm at F/1.4

Thanks! Bokeh rendering and contrast+colours look good, but DOF must be razor thin (unsurprisingly). I guess focus peaking on the NEX comes into its element with a speed booster and the 85/1.4.

[devorama]

Thanks! Bokeh rendering and contrast+colours look good, but DOF must be razor thin (unsurprisingly). I guess focus peaking on the NEX comes into its element with a speed booster and the 85/1.4.

Yes, with the lens turbo and the 85mm, it's almost impossible to get both eyes sharp unless the subject is staring straight into the camera. If you look closely, the left eye is not really sharp, but it's not as noticeable because it's the side opposite the key light.

[devorama]

Any chance you could post a 100% crop? The resizing/compression software on thi forum always makes everything look soft, so it's hard to get a good handle on true sharpness.

Sure thing. This is a 100% crop. This is from the Sony NEX-3 JPG source, so some sharpening was probably already applied. Shot at ISO 400.

[VisualDarkness]

Hey, I want one for my Q! Are you listening Metabone or random Chinese makers?

[Sliver-Surfer]

Hey, I want one for my Q! Are you listening Metabone or random Chinese makers?

If you concentrate the light from a fast fifty onto a Q sensor your liable to start a fire.

[VisualDarkness]

If you concentrate the light from a fast fifty onto a Q sensor your liable to start a fire.

It would be a really hot item indeed!

[Sliver-Surfer]

Seriously, though, I think I recall reading on another forum that the Metabones guys had stated that they weren't able to successfully push their design past a 50% reduction. So while a Q mount item would be possible, it would be only a partial reduction. Given the limited low light capabilities of the Q sensor, this still might be useful, but the gains might also be offset by the reduction in sharpness caused by the added glass.

My dream camera if I could put myself in a pentax engineers shoes and build my own. Mirrorles pentax K01-2.0, slimmer front to back body, interchangeable removeable PKA-body adapter, with optional Speed booster PKA-body WR adapter . Electronic viewfinder a must

[devorama]

I was doing some quick testing of the Lens Turbo and my Pentax 50mm F/1.2 lens. At F/2.8, using the Lens Turbo vs a regular lens adapter (with no glass), it appears that a similarly composed image will gain about 2/3 stop of light with the lens turbo. However, if you are using a lens that vignettes heavily, you won't gain 2/3 stop. Using the lens at F/1.2 and multi-segment metering, the NEX-3 I was using metered the same exposure with or without the Lens Turbo. Switching to Spot Metering gave me back 1/3 stop though. Kinda interesting. But if you really want to use the Lens Turbo to get better low light abilities, you may not really be gaining much. You'd probably be shooting your lenses wide open already, which means the part of the image circle you're now capturing will be heavily vignetted.

[jogiba]

Hey, I want one for my Q! Are you listening Metabone or random Chinese makers?

Meade makes a F3.3 focal reducer ( 100mm = 33mm ) F10 = F3.3.
Meade f/3.3 CCD Focal Reducer/Field Flattener and Variable T-Adapter - Telescope Accessories at Telescopes


Meade F3.3 Focal Reducer on Nikon D200 APS-C. On the Q it will not vignette

[konraDarnok]

I was doing some quick testing of the Lens Turbo and my Pentax 50mm F/1.2 lens. At F/2.8, using the Lens Turbo vs a regular lens adapter (with no glass), it appears that a similarly composed image will gain about 2/3 stop of light with the lens turbo. However, if you are using a lens that vignettes heavily, you won't gain 2/3 stop. Using the lens at F/1.2 and multi-segment metering, the NEX-3 I was using metered the same exposure with or without the Lens Turbo. Switching to Spot Metering gave me back 1/3 stop though. Kinda interesting. But if you really want to use the Lens Turbo to get better low light abilities, you may not really be gaining much. You'd probably be shooting your lenses wide open already, which means the part of the image circle you're now capturing will be heavily vignetted.

mind posting a side by side? I'm curious how it effects the field of view and the depth of field.

[jedie]

My dream camera if I could put myself in a pentax engineers shoes and build my own. Mirrorles pentax K01-2.0, slimmer front to back body, interchangeable removeable PKA-body adapter, with optional Speed booster PKA-body WR adapter . Electronic viewfinder a must

Great idea! I must not have a EVF... Can live without it on my K-01 very well...