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05-29-2018, 06:57 AM   #1
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Nocturnus 50 mm f0.95

Nocturnus 50 DSLR Presale
If you have money to burn..........

Comes in pentax mount.

05-29-2018, 07:45 AM   #2
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Pentax K mount limits the aperture to F1.2 by it's size.
The equation is here: Lens speed - Wikipedia

I don't know how this affects the bokeh, but the light gethering "working f-number" is limited.
05-29-2018, 12:03 PM   #3
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QuoteOriginally posted by 08amczb Quote
Pentax K mount limits the aperture to F1.2 by it's size.
The equation is here: Lens speed - Wikipedia

I don't know how this affects the bokeh, but the light gethering "working f-number" is limited.

There were a few 1.2 M42 lenses, too. I'm sure the M42 mount doesn't get all the benefit of a 1.2 lens either.
05-29-2018, 12:37 PM   #4
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QuoteOriginally posted by 08amczb Quote
Pentax K mount limits the aperture to F1.2 by it's size.
The equation is here: Lens speed - Wikipedia

I don't know how this affects the bokeh, but the light gethering "working f-number" is limited.
Whoa! thanks for telling this

05-29-2018, 01:31 PM - 1 Like   #5
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QuoteOriginally posted by D4rknezz Quote
Whoa! thanks for telling this
So essentially you are buying a very expensive pentax A 50mm 1.2 ?
05-29-2018, 01:41 PM   #6
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QuoteOriginally posted by timw4mail Quote
There were a few 1.2 M42 lenses, too. I'm sure the M42 mount doesn't get all the benefit of a 1.2 lens either.
The M42 mount hass approximetly the same limit. You can calculate the actual value as (flange focal distance)/(rear element diameter) if you substitutes the sin in the equation by (half rear element diameter)/(flange focal distance).
The M42 mount has a diameter of 42mm, so I can imagine a 38mm rear lens element plus the 2mm screw all around to mount the lens. The FFD is 45.46mm and it gives 45.46/38=1.1963, so F1.2 as limit. The bayonet requires more metal around the rear elemnt to work, so the limit is approximetly the same.
Nikon F mount gives the same F1.2, Canon EF gives F1.0. M43 has a limit at F0.65 if I calculate correctly. There is a hard limit at F0.5, any lens faster then F0.5, nothing can be made that fast with air gap between the lens and the sensor.

---------- Post added 05-29-18 at 10:44 PM ----------

QuoteOriginally posted by bavd Quote
So essentially you are buying a very expensive pentax A 50mm 1.2 ?
I think yes. And my educated gess about the bokeh is the same, it's limited to F1.2 I think. (but I'am not 100% sure)
05-30-2018, 05:55 AM   #7
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QuoteOriginally posted by bavd Quote
So essentially you are buying a very expensive pentax A 50mm 1.2 ?
Well....
I dont think meyer optic releases anything with A setting, so its more like, an M 1.2.
I like the lenses i got from them, but maybe not for $2k.
05-30-2018, 06:28 AM   #8
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QuoteOriginally posted by D4rknezz Quote
Well....
I dont think meyer optic releases anything with A setting, so its more like, an M 1.2.
I like the lenses i got from them, but maybe not for $2k.

These are probably stop-down-only lenses. I would be surprised if they actually have aperture couplings to the mount.

05-31-2018, 11:05 AM - 1 Like   #9
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QuoteOriginally posted by 08amczb Quote
Pentax K mount limits the aperture to F1.2 by it's size.
The equation is here: Lens speed - Wikipedia

I don't know how this affects the bokeh, but the light gethering "working f-number" is limited.
I don't see anything saying what the K Mount is limited to, all it says is most SLR mounts are limited to f1.0 to f1.2

Do you have the numbers for the K mount to plug into the equation?
05-31-2018, 03:29 PM   #10
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Okey, so after some reserching: the effective aperture is limited by the mount, so the light gethering capability is limited to T1.2, but it does not apply to the bokeh. So the lens can wash out more background than the A50 F1.2!

QuoteOriginally posted by ZombieArmy Quote
Do you have the numbers for the K mount to plug into the equation?
The flange focal distance is 45.46 and the diameter is about 39mm if you meassure and substruct the nececery space for fixing the lens. You can calculate the sin as (half diameter)/(FFD). The substitution gives 45.46/39 = 1.1656, so approx F1.2.
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