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03-07-2010, 10:05 AM   #1
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C'mon Pentax, it's time for a DA* 50mm F1.0

Lets face it Pentax, our options for 3rd party lenses are limited. We're a captive audience. Oh and lets not forget, we're suckers for something shiny.

We're unable to get an F1.0 lens for our cameras, and we want them. Other brands have them, but alas, not us.

Why do we want this lens? We don't really know, but if you sell them, we're almost guaranteed to buy them.

Just look at the prices of the manual focus Pentax-A F1.2 lenses on ebay these days. The seller that imports the new ones from Vietnam has sold them them for $999. Even the full manual f1.2 lenses from the 80s with stop down metering sell for more than $350!

I'll admit, I'm a sucker like most here, and I'd like to buy one for $800, but I suspect you'd still be able to sell them in bulk for $1000.

Really want to make us drool and go crazy with excitement? Feel free to take it even farther, up to a F0.85 or to 77mm.

Oh Tamron & Sigma, feel free to beat Pentax to this punch, just make the lens in our mount.

So, quit sandbagging. You make them, you sell them, and we'll buy them. Nuff said.

03-07-2010, 10:11 AM   #2
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How would a F0.85 work? I thought I understood at f1 100% of the light hit the sensor, so would F0.85 be more than the max ambient light?
03-07-2010, 10:17 AM   #3
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I dont believe the kmount would allow for a sub 1.0 aperture. I could be wrong, but I think I remember that being mentioned here. in fact,I believe I have read that 1.2 is about the max you can have on a Kmount lens. again I could be wrong, but it maybe worth doing a forum search about it.
03-07-2010, 10:37 AM   #4
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This approaching deserving of a separate thread...

There's some videos on youtube where people have adapted the C mount 28mm F0.85 lenses (to a non pentax camera) and shot video in the dead of night with them. ( YouTube - Panasonic Lumix GH1 + Tarcus 25mm f0.85 - Low Light ) Conceptually a fun idea, although I imagine the quality is bunk. There's an interesting pic of a F0.85 lens here: Leitz 75mm f0.85 | photostream

Ultimately I'd be happy with some F1.0 action though.

03-07-2010, 10:52 AM   #5
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I think the IQ is more important than a small F value for a lens. For some lens, though they got the maximum aperture as 1.4, but always we use it at 2.8 for a sharp shot and beautiful bokeh. So I think I would prefer those lens with smaller aperture, but they can do pretty well at maximum aperture. For example, I prefer DA 35 than FA 35, DFA 50 than FA 50.
03-07-2010, 10:53 AM   #6
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QuoteOriginally posted by icywarm Quote
How would a F0.85 work? I thought I understood at f1 100% of the light hit the sensor, so would F0.85 be more than the max ambient light?
Not quite - F stops is basically the focal length divided by the diameter of the lens opening (which allows light through to the sensor, film, etc). Here's a few links on the subject.

Aperture - Simple English Wikipedia, the free encyclopedia
f-Stop Table

Simply put, yes it's possible to go below F/1, but you need to use a lot of glass. Next question - would you pay the asking price if it came out? I highly doubt most users would...
03-07-2010, 11:11 AM   #7
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QuoteOriginally posted by séamuis Quote
I dont believe the kmount would allow for a sub 1.0 aperture. I could be wrong, but I think I remember that being mentioned here. in fact,I believe I have read that 1.2 is about the max you can have on a Kmount lens. again I could be wrong, but it maybe worth doing a forum search about it.
You aren't wrong. It has been discussed here before. Remember the whole D-FA 50mm 1.0 roadmap hoax? This post simply explains why K-Mount f1.0 is nearly impossible:

https://www.pentaxforums.com/forums/611694-post148.html


QuoteQuote:
Regarding an f/1.0 lens from Pentax: The 50mm f/1.4 has a rear element ~29mm in diameter, giving it an area of 660.5 sq.mm. The 50mm f/1.2 has a rear element diameter of ~35.5mm, giving it an area of 989.8 sq.mm. These numbers make sense: f/1.2 is 1/2 stop faster than f/1.4, so the area of its rear element should be 1.5 times larger; and it is.

A 50mm f/1.0 lens would have a rear element twice the area of the f/1.4, which would mean its diameter would have to be square root of 2 larger. That gives us ~41mm. Take any K mount lens and measure that width; you'll see that the aperture lever would have to be removed in order to have a rear element that large and the glass would be very near the edge of the mount.
03-07-2010, 02:01 PM   #8
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QuoteOriginally posted by henryjing Quote
I think the IQ is more important than a small F value for a lens. For some lens, though they got the maximum aperture as 1.4, but always we use it at 2.8 for a sharp shot and beautiful bokeh. So I think I would prefer those lens with smaller aperture, but they can do pretty well at maximum aperture. For example, I prefer DA 35 than FA 35, DFA 50 than FA 50.
Interesting point! I recently sold my FA 50 because although it was a 1.4 aperture, wide open it was very soft and lacked contrast. (Maybe just sample variation, who knows?) Sure, it was VERY sharp, stopped down, but at least for me, that's not the purpose of fast glass!

Another couple threads have questioned FA 50 vs. DA*55 vs. Sigma 1.4 HSM. Personally I'm not too keen on the price of the DA*55, but from what I've read, the Sigma has been designed for improved performance at maximum aperture. I think Pentax missed the boat with the DA*55 because for most people, paying at least twice the value of an FA 50 does not equate to twice the image quality (recent bokeh examples not withstanding!).

03-07-2010, 02:29 PM   #9
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QuoteOriginally posted by MrApollinax Quote
You aren't wrong. It has been discussed here before. Remember the whole D-FA 50mm 1.0 roadmap hoax? This post simply explains why K-Mount f1.0 is nearly impossible:

https://www.pentaxforums.com/forums/611694-post148.html
Something to consider: If it were truly a DA lens, then the image circle wouldn't need to be as large as an FA lens, so they should be able to get by with less glass. Not sure how it would work out, but it may not be impossible to make an F1.0 DA lens, even if an F1.0 FA lens is impossible. Or they could at least theoretically make a DA 35mm F1.0 lens, which if made for APS-C should be about the same dimensions as an FA 50mm F1.4. And it would give the same image output in terms of DOF and FOV.
03-07-2010, 06:52 PM   #10
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I would rather have an F/1.4 lens that is sharp wide open then the F/1.0 that is soft, but then I wouldn't want to give up an arm and a leg to play at F/1.0.
03-09-2010, 09:11 PM   #11
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What if it's a F/1.0 lens that's (maybe) a little soft wide open, but by the time you stop it down to F1.4 it's wicked sharp?
03-09-2010, 09:26 PM   #12
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It would be better to release cheap (200USD) 50 f1,7 a 35 f2 that would sell like hot cakes than yet another super expensive prime.
03-11-2010, 12:48 PM   #13
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I'd take a f1.0 35mm over 50mm any day since it's a more practical focal length on cropped sensors.
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