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06-24-2018, 07:14 PM - 1 Like   #31
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QuoteOriginally posted by Abbazz Quote
It must be doable but maybe not as easy as it seems.

When I received the Pentax Q SpeedBooster, it was not able to properly focus to infinity: max focus was about 30 meters, which makes quite a difference with a 55mm lens at F/1.2. I had to adjust the infinity focus as per the procedure outlined on the Metabones website. This was a bit tricky because I found out that if you oudo the adjustment just a little bit, it can prevent your SpeedBooster from focusing properly. But I guess it means you could replace the Nikon bayonet with a Pentax one and then carefully adjust the focus on the adapter to compensate for the small difference in backfocus between Nikon and Pentax mounts.

Maybe I will try it some day.

Cheers!

Abbazz
Thank you. Your experience has more dimensions than I had realized.

06-25-2018, 10:07 AM   #32
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As an added comment, I should say I'm not sure this really has much practical use. The '06' lens is already f/2.8, so a 50mm f/1.4 lens on this gains little added shutter speed or little lowered ISO setting, loses some DOF, and loses AF.
06-25-2018, 11:27 AM   #33
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QuoteOriginally posted by reh321 Quote
As an added comment, I should say I'm not sure this really has much practical use. The '06' lens is already f/2.8, so a 50mm f/1.4 lens on this gains little added shutter speed or little lowered ISO setting, loses some DOF, and loses AF.
And the added shutter speed is electronic. Which doesn't stop motion as well as a true mechanical shutter. Try shooting spinning fan blades with electronic shutter. Distorted.
Thanks,
barondla
06-25-2018, 03:27 PM - 1 Like   #34
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QuoteOriginally posted by reh321 Quote
As an added comment, I should say I'm not sure this really has much practical use. The '06' lens is already f/2.8, so a 50mm f/1.4 lens on this gains little added shutter speed or little lowered ISO setting, loses some DOF, and loses AF.
The 06 lens gives you F/2.8 at its max focal length, which is 45mm. A 50/1.4 lens used with the SpeedBooster gives you F/0.7 at 50mm: that's a 4 stop difference, which is quite appreciable when the light is low!

For example, if you shoot a concert at F/2.8 and 3200 ISO with the 06 lens in order to get an acceptable shutter speed of 1/125s, then if you were shooting the same concert with the SpeedBooster and a 50/1.4 lens, you could have used F/0.7 and 200 ISO with the same shutter speed of 1/125s or opted for 400 ISO and a safer 1/250s shutter speed...

Cheers!

Abbazz


Last edited by Abbazz; 06-25-2018 at 05:46 PM.
07-05-2018, 07:31 PM   #35
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QuoteOriginally posted by Abbazz Quote
a 55mm lens on a full frame sensor is "equivalent" to a 27.5mm lens on a M4/3 format sensor.
No, it absolutely does NOT.
No crop sensors can ever make a Lens appear to be wider then what that lens is natively.
Not even when a Focal Reducer is used.
You need to go back an redo all your maths, because you have it the wrong way around.

---------- Post added 06-07-18 at 12:41 PM ----------

QuoteOriginally posted by reh321 Quote
The speedbooster does physically change the optical characteristics of the lens; light does follow a different path than it had. A 55mm lens does become a 27.5mm lens, because the path of light through it is changed.Any lens becomes wider and it delivers a higher intensity beam to the sensor. Always.
Nope.
A 55mm lens is always a 55mm lens, regardless of whether it's mounted on a FF, MF, APSc, Q or even sitting on the floor.
The lens's angle of view is always the same.
The use of a focal reducer compresses the image circle - it paints a smaller circle of the same angle of view.

Hold a lens up so the front faces an open window while standing in the door way to a darkend hallway.
Now hold a piece of paper up behind the lens and move it closer or further away until the lens is projecting a sharp image on the paper.
Note what items are in view, and the size of the circular image.

Now add your focal reducer to the back of the lens and repeat.
You will see the same items in view, but the circle will be smaller.

You only see more of the image circle on a crop sensor camera because the image circle is projected smaller.

You do not see more items projected then before.

It's simply that the camera can now see more of what the lens could already see. This is what makes people think the lens magically becomes wider, but it does not.


Use of a Focal Reducer means less of the image circle is lost.

---------- Post added 06-07-18 at 12:55 PM ----------

QuoteOriginally posted by 2old4toys Quote
Forgive extreme naivety but what challenges are there to physically remove the Nikon Mount and swap in a PK Mount instead,
QuoteOriginally posted by reh321 Quote
Are you suggesting that someone, some amateur here, spend $489 on one of these devices and then modify it so that provides a K-mount instead of a F-mount?


I thought about it for a long while, especially as they make C/Y to M4/3 and C/Y to E Speedboosters, as the C/Y lenses used the same FFD as K-mount and M42.

Since I made M4/3 and E mounts for my Aja Cion, I was asked by a US cinematographer if I could modify one of the PL to E speedboosters, and found it would be easier to pull the rear off the Speedbooster and manufacture a custom plate that would screw directly in to the rear flange mount, instead of using the E-mount.

Turning one of the C/Y to M4/3, E, X mounts Speedboosters in to a K-mount would be even easier, as I could pull the K-mount ring off the front of a cheap adapter, redrill the screw holes to match the Speedbooster, block the original holes if not used, and then just screw it in place.

I've been half tempted to create a range of custom fit lens flange rings, but have been busy with other needs.

Modifying the Speedbooster for a Q, to accept K-mount lenses, is basically the same, but the front ring would be much narrower, due to the longer FFD of the Nikon lenses.


The other option for K lenses on M4/3 and E mounts, is to buy one of the Kipon Focal Reducers - Kipon use the same optical supplier as Arri.
Sadly they don't make a product for the Q or Nikon 1 series.

I'd expect to see Metabones never make a K-mount version, but will probably make a version for the Nikon 1 cameras.

Having used both, the Q family are superior, even when comparing Video output.

Last edited by PiDicus Rex; 07-05-2018 at 08:00 PM.
07-05-2018, 08:12 PM   #36
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QuoteOriginally posted by PiDicus Rex Quote
No, it absolutely does NOT.
No crop sensors can ever make a Lens appear to be wider then what that lens is natively.
Not even when a Focal Reducer is used.
You need to go back an redo all your maths, because you have it the wrong way around.

---------- Post added 06-07-18 at 12:41 PM ----------


Nope.
A 55mm lens is always a 55mm lens, regardless of whether it's mounted on a FF, MF, APSc, Q or even sitting on the floor.
The lens's angle of view is always the same.
The use of a focal reducer compresses the image circle - it paints a smaller circle of the same angle of view.

Hold a lens up so the front faces an open window while standing in the door way to a darkend hallway.
Now hold a piece of paper up behind the lens and move it closer or further away until the lens is projecting a sharp image on the paper.
Note what items are in view, and the size of the circular image.

Now add your focal reducer to the back of the lens and repeat.
You will see the same items in view, but the circle will be smaller.

You only see more of the image circle on a crop sensor camera because the image circle is projected smaller.

You do not see more items projected then before.

It's simply that the camera can now see more of what the lens could already see. This is what makes people think the lens magically becomes wider, but it does not.

Use of a Focal Reducer means less of the image circle is lost.
What do you mean by "wider"?

What do you mean by " camera can now see more of what the lens could already see"?

Remember that we are using a lens designed for a larger sensor on a camera with a smaller sensor.
Normally when we do that, most of the light provided by the lens is lost.
07-05-2018, 08:17 PM   #37
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QuoteOriginally posted by PiDicus Rex Quote
No, it absolutely does NOT.
No crop sensors can ever make a Lens appear to be wider then what that lens is natively.
Not even when a Focal Reducer is used.
You need to go back an redo all your maths, because you have it the wrong way around.

---------- Post added 06-07-18 at 12:41 PM ----------


Nope.
A 55mm lens is always a 55mm lens, regardless of whether it's mounted on a FF, MF, APSc, Q or even sitting on the floor.
The lens's angle of view is always the same.
The use of a focal reducer compresses the image circle - it paints a smaller circle of the same angle of view.

Hold a lens up so the front faces an open window while standing in the door way to a darkend hallway.
Now hold a piece of paper up behind the lens and move it closer or further away until the lens is projecting a sharp image on the paper.
Note what items are in view, and the size of the circular image.

Now add your focal reducer to the back of the lens and repeat.
You will see the same items in view, but the circle will be smaller.

You only see more of the image circle on a crop sensor camera because the image circle is projected smaller.

You do not see more items projected then before.

It's simply that the camera can now see more of what the lens could already see. This is what makes people think the lens magically becomes wider, but it does not.


Use of a Focal Reducer means less of the image circle is lost.

---------- Post added 06-07-18 at 12:55 PM ----------







I thought about it for a long while, especially as they make C/Y to M4/3 and C/Y to E Speedboosters, as the C/Y lenses used the same FFD as K-mount and M42.

Since I made M4/3 and E mounts for my Aja Cion, I was asked by a US cinematographer if I could modify one of the PL to E speedboosters, and found it would be easier to pull the rear off the Speedbooster and manufacture a custom plate that would screw directly in to the rear flange mount, instead of using the E-mount.

Turning one of the C/Y to M4/3, E, X mounts Speedboosters in to a K-mount would be even easier, as I could pull the K-mount ring off the front of a cheap adapter, redrill the screw holes to match the Speedbooster, block the original holes if not used, and then just screw it in place.

I've been half tempted to create a range of custom fit lens flange rings, but have been busy with other needs.

Modifying the Speedbooster for a Q, to accept K-mount lenses, is basically the same, but the front ring would be much narrower, due to the longer FFD of the Nikon lenses.


The other option for K lenses on M4/3 and E mounts, is to buy one of the Kipon Focal Reducers - Kipon use the same optical supplier as Arri.
Sadly they don't make a product for the Q or Nikon 1 series.

I'd expect to see Metabones never make a K-mount version, but will probably make a version for the Nikon 1 cameras.

Having used both, the Q family are superior, even when comparing Video output.
Are you saying that if I put a 35mm f/2 lens set at widest aperture on my Q-7, my camera will not act as though lens were set at f/1?

07-06-2018, 02:05 PM   #38
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Equivalance discussions always spoil the fun.
07-07-2018, 05:34 AM - 1 Like   #39
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QuoteOriginally posted by Mikesul Quote
Equivalance discussions always spoil the fun.
Especially since we seem to have forgotten how this thread began.

The OP did some actual "lab work", not calculations, and the results are simple and straight-forward:

I printed out two of the photos, which from the text were taken from the same position

(a) the one labeled "55mm F/2.0", which used the 55mm lens mounted on the Q via a standard glassless adapter
(b) the one labeled "27.5mm F/1.0", which used the 55mm lens mounted on the Q via the DSB
Each photo contains a color-checker, and there are two vertical lines in the vicinity. In (a) the lines make up roughly 1/2 the width of the photo, and in (b) the lines make up roughly 1/4 the width of the photo. Since these two photos were taken from the same position, empirically we can say that with the DSB we got the same photo we would have gotten with a 27.5mm lens.

Of course, the lens itself hasn't changed, but when it is mounted via the DSB we can reach the following conclusions comparing it to mounting via a standard adapter

(1) it shows a view which is twice as wide

(2) "there is a gain of almost two stops, as per the specs."
07-07-2018, 07:23 AM - 1 Like   #40
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Thanks for doing this, reh321. Over all the years of discussion and enthusiasm for speed boosters in mirrorless circles I do not recall reading about as coherent a test as this. Empirical evidence is always the most reliable.
10-11-2018, 09:47 AM   #41
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I still want one of these for my K-mount lenses.... it'd be worth the high cost, even without a mechanical shutter.

Charles
10-11-2018, 04:28 PM - 1 Like   #42
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QuoteOriginally posted by ChopperCharles Quote
I still want one of these for my K-mount lenses.... it'd be worth the high cost, even without a mechanical shutter.
Pentax K bayonet register (45.46mm) is very close to Nikon F (46.5mm). I think it must be possible to exchange the Nikon F mount on the SpeedBooster for a Pentax K mount and then adjust the optical unit (as per the procedure on the Metabones website) to compensate for the difference in register.

Cheers!

Abbazz
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