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Nikkor-S 55mm F/1.2 on Pentax Q with Devil's Speed Booster
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PostPosted: Thu Oct 12, 2017 8:26 am    Post subject: Nikkor-S 55mm F/1.2 on Pentax Q with Devil's Speed Booster Reply with quote
Here are some pictures taken with the "Devil's Speed Booster", a focal reducer specially crafted for the Pentax Q line of cameras.

The Pentax Q is a pretty unique camera series that offers an interchangeable lens body with advanced features (sensor based image stabilization, RAW image processing) with a small sensor (1/2.3" for the Pentax Q and Pentax Q10 or 1/1.7" for the Pentax Q7 and Pentax Q-S1).

Recently, a focal reducing adapter (a.k.a. Speed Booster or Lens Turbo) was made available for the Pentax Q mount, allowing to adapt Nikon lenses to the small sensor cameras. The unique ability of this adapter is to half the focal length of the lens and also to gain two aperture stops in the process. For example, a 50mm F/2.0 lens will become a 25mm F/1.0 lens. Of course, the small sensor of the Pentax Q cameras will imply that the angle of view will still be smaller than the AOV of the 50mm lens on a 24x36 "full-frame" camera. but the two aperture stops bonus is still a very tempting proposition.

So I decided to try the Devil's Speed Booster on one of my Pentax Q-S1 cameras. Of course, I chose my fastest lens in Nikon mount, a vintage Nikkor-S 55mm F/1.2. The "Devil's Speed Booster" is so named because its effective aperture is limited to F/0.666, whatever the max aperture of the lens mounted on it. So my F/1.2 lens will only have an F/0.67 max aperture. So be it!

Here are the pictures, all taken wide open at F/1.2, err, sorry F/0.67. It was raining and the light was particularly dull:











Cheers!

Abbazz


PostPosted: Thu Oct 12, 2017 11:50 am    Post subject: Reply with quote
Like 1 wait for more, coul you check some 200mm lenses? Smile


PostPosted: Fri Oct 13, 2017 9:35 am    Post subject: Reply with quote
Piotr Krochmal wrote:
Like 1 wait for more, coul you check some 200mm lenses? Smile

The longest lens I have in Nikon mount is the 105/2.5. I will test it if I can locate the lens in the boxes I have in storage...

Cheers!

Abbazz


PostPosted: Fri Oct 13, 2017 3:38 pm    Post subject: Reply with quote
Honestly Sebastien, I would have expected a bit better contrast...
Nevertheless, great results! Like 1 small Like 1 small Like 1 small


PostPosted: Fri Oct 13, 2017 11:14 pm    Post subject: Reply with quote
Is the Nikkor 1.2/55 really so bad? I see no sharpness, low contrast, washed out colours, not good at all. Or is the speed booster to blame?


PostPosted: Sat Oct 14, 2017 7:19 am    Post subject: Reply with quote
My Nikkor S.C 55/1.2 has lots of glow wide open, contrast is low, but is still quite sharp(threads right of the mouth in the last pic), it's very different one click down, it's ideal for soft portraits, it would match nicely with a soft 85.


PostPosted: Tue Oct 17, 2017 10:28 am    Post subject: Reply with quote
kds315* wrote:
Honestly Sebastien, I would have expected a bit better contrast...
Nevertheless, great results! Like 1 small Like 1 small Like 1 small

Thanks for the kind words, Klaus.

iangreenhalgh1 wrote:
Is the Nikkor 1.2/55 really so bad? I see no sharpness, low contrast, washed out colours, not good at all. Or is the speed booster to blame?

Lightshow wrote:
My Nikkor S.C 55/1.2 has lots of glow wide open, contrast is low, but is still quite sharp(threads right of the mouth in the last pic), it's very different one click down, it's ideal for soft portraits, it would match nicely with a soft 85.


My Nikkor-S exhibits a lot of spherical aberration and coma wide open, even on a 24x36 camera. The images also tend to have a purplish cast. It can be used for portrait work in B&W but needs to be stopped down a bit to deliver a sharp image.

Here it is on the Pentax Q wide open with the Speed Booster (F/0.66):


Stopped down to F/2.8 (F/1.4 with the Speed Booster):


One more, wide open with the Speed Booster (F/0.66):


Stopped down to F/2.8 (F/1.4 with the Speed Booster):


And the last one, wide open with the Speed Booster (F/0.66):


Stopped down to F/2.8 (F/1.4 with the Speed Booster):


All these pictures are JPEGs straight from the camera (which means I didn't adjust the color balance as I would normally do -of course these tomatoes are not the right color). Also note that the crop factor of the Pentax Q (x2.3 with the speed booster) tends to amplify the aberrations of the lens mounted.

Cheers!

Abbazz


PostPosted: Tue Oct 17, 2017 7:43 pm    Post subject: Reply with quote
Wow, looks like a cool gadget! I once shot Pentax APS-c, even put some of my medium-format Pentax glass on the APS_c sensor via an adapter--setup looked like a weapon of mass destruction LOL.

Anyway, like your results, but questions--how are the corners and how is vignetting? jt


PostPosted: Wed Oct 18, 2017 12:40 am    Post subject: Reply with quote
Focusthrow wrote:
Anyway, like your results, but questions--how are the corners and how is vignetting? jt

Thank you for the compliment.

You can check vignetting on the samples I posted, as the vignetting has not been corrected at all (click on the images to view full size originals). As for corners resolution, the Speed Booster has a remarkably low impact. Of course an F/1.2 lens used wide open will not have an impressive resolution outside of the very center of the frame, but at least the worst area will be cropped out, thanks to the 2.3 crop factor of the Q7/Q-S1.

Cheers!

Abbazz


PostPosted: Thu Oct 19, 2017 7:02 pm    Post subject: Reply with quote
Abbazz wrote:
Focusthrow wrote:
Anyway, like your results, but questions--how are the corners and how is vignetting? jt

Thank you for the compliment.

You can check vignetting on the samples I posted, as the vignetting has not been corrected at all (click on the images to view full size originals). As for corners resolution, the Speed Booster has a remarkably low impact. Of course an F/1.2 lens used wide open will not have an impressive resolution outside of the very center of the frame, but at least the worst area will be cropped out, thanks to the 2.3 crop factor of the Q7/Q-S1.

Cheers!

Abbazz


Abbazz: There are a few reasons I asked about corner sharpness & vignetting. The 1st is some who use a Turbo Booster on APS-c express a concern with corners/vignetting: was curious what results were like on the Q7/Q-S1. The other is because I wasn’t sure if you were posting crops: many people at forums post crops, but do not say the samples are crops. Also, like you say, your samples are all wide open, which is not a way to check corner performance. I do not want or need good corners on my fast glass wide open or even stopped down some, but by f/4 or f/5.6 I begin to expect good corners.

1 more question: when you shoot glass without the TB, the smaller sensor does what crop sensors do--adjusts FOV to accommodate the sensor’s size. However, with the TB’s reversal of the crop effect, what costs are incurred on image quality? Photography, like life, teaches us choices have consequences--some pluses, some minuses. For a simple example, to get a faster shutter speed, one sacrifices either the depth of the focal plane, or IQ due to higher ISO. Of course, modern DSLRs are a boon for increasing the sensitivity of light without as much sacrifice (in IQ) as we endured in film. But the point is (in the words of my Economics 101 professor) “Everything has a cost."

Sometimes I shoot, via adapters, my XE-1 with full-frame glass & have been intrigued with picking up a Turbo Booster for the benefits you describe above. How much weight does your TB add to your setup? Thanks for the post & response--it helps bring me closer to an informed decision on a TB. Best, jt


PostPosted: Fri Oct 20, 2017 11:01 am    Post subject: Reply with quote
Focusthrow wrote:
Abbazz: There are a few reasons I asked about corner sharpness & vignetting. The 1st is some who use a Turbo Booster on APS-c express a concern with corners/vignetting: was curious what results were like on the Q7/Q-S1. The other is because I wasn’t sure if you were posting crops: many people at forums post crops, but do not say the samples are crops. Also, like you say, your samples are all wide open, which is not a way to check corner performance. I do not want or need good corners on my fast glass wide open or even stopped down some, but by f/4 or f/5.6 I begin to expect good corners.

The vignetting is negligible on the Q series cameras. Because of the crop factor (5.6 on the Q or Q10 and 4.6 on the Q7 and Q-S1), only the center part of the image circle of the lens is used. Therefore, there is absolutely no vignetting when using lenses designed for 24x36 "full-frame" format on the Q series cameras. And the Devil's Speed Booster (DSB) doesn't add any vignetting to the mix.

Regarding corner sharpness, there is no specific degradation due to the use of the DSB. As a focal reducer, the DSB uses a larger part of the image circle of the lens, so the corners of the image can indeed be less sharp than when using the bare lens without the DSB. But this is due to the lack of sharpness of the lens outside of the center of the frame, and not to the DSB itself.

Focusthrow wrote:
1 more question: when you shoot glass without the TB, the smaller sensor does what crop sensors do--adjusts FOV to accommodate the sensor’s size. However, with the TB’s reversal of the crop effect, what costs are incurred on image quality? Photography, like life, teaches us choices have consequences--some pluses, some minuses. For a simple example, to get a faster shutter speed, one sacrifices either the depth of the focal plane, or IQ due to higher ISO. Of course, modern DSLRs are a boon for increasing the sensitivity of light without as much sacrifice (in IQ) as we endured in film. But the point is (in the words of my Economics 101 professor) “Everything has a cost."

In fact, the DSB, like other focal reducers, tends to enhance image sharpness. It degrades the lateral chromatic aberration though.

Focusthrow wrote:
Sometimes I shoot, via adapters, my XE-1 with full-frame glass & have been intrigued with picking up a Turbo Booster for the benefits you describe above. How much weight does your TB add to your setup? Thanks for the post & response--it helps bring me closer to an informed decision on a TB. Best, jt

The added weight compared to a bare adapter is pretty much negligible. The Metabones Speed Booster is a good product but you can save a lot of money with buying a Zhongyi lens Turbo II if you want to use it on a Fuji APS-C camera.

Cheers!

Abbazz


PostPosted: Fri Oct 20, 2017 11:14 am    Post subject: Reply with quote
I have yet to see any evidence that a speed booster 'enhances sharpness', quite the opposite in fact as they increase whatever aberrations are present.

The Q7 I have, with it's 1/1/7" sensor and no AA filter is capable of very sharp results, but it needs a very high resolution lens to do so, due to the tiny pixel size.

I don't see any use for a speed booster on the Q as there are so many fast C mounts in the 1.2-1.4 range, not all of them are high enough resolution though.


PostPosted: Fri Oct 20, 2017 11:17 am    Post subject: Reply with quote
iangreenhalgh1 wrote:
I have yet to see any evidence that a speed booster 'enhances sharpness', quite the opposite in fact as they increase whatever aberrations are present.

The Q7 I have, with it's 1/1/7" sensor and no AA filter is capable of very sharp results, but it needs a very high resolution lens to do so, due to the tiny pixel size.

I don't see any use for a speed booster on the Q as there are so many fast C mounts in the 1.2-1.4 range, not all of them are high enough resolution though.

You might want to have a look there: https://www.pentaxforums.com/forums/136-pentax-q/354465-0-666-devils-speed-booster-pentax-q.html

Cheers!

Abbazz
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