2,000mm f13.5 SMC-M on eBay

K David · 04-09-2015, 07:33 PM

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.

Asahi Pentax SMC M 2000mm F13 5 Reflex Lens Nikon F Adapter for Pentax K | eBay

Not sure if anyone saw this, but if you have $12K to spare, go for it. It's interesting to see some other photos of this lens. I'd love to see what kind of photos it can take.

No affiliation with the seller.

calsan · 04-09-2015, 07:43 PM

Seems a big bunch of money for a mirror lens.

DeadJohn · 04-09-2015, 07:51 PM

*Definitely* not worth it unless you're a collector. Save $11000 and buy a new 2000mm f10 telescope

C8-A XLT (CGE) Optical Tube Assembly [item # 91024-XLT]

honey bo bo · 04-09-2015, 09:12 PM

Just got a fun mirror lens for $100 - Bausch & Lomb Criterion 4000 1200mm mirror X $20 Toyo 2 X Pusher = 2400 mm and it actually works; Sort of !
All for $120 I'm looking forward to warmer weather so that I can get my money's worth.. Boy the SR is smoking trying to keep up with Shake Rattle and Roll going on at that length.
That's 3600mm before the turn of the century.

---------- Post added 04-10-15 at 12:47 AM ----------

By the way those pics aren't hand held. The whole thing is securely attached to a $15 Velbon Challenger tripod with a 40km breeze.
I think I could smell rubber burning from my K3 and it's in house SR and photo pride system trying to make a bad situation OK!

Attached Images

View Picture EXIF

View Picture EXIF

Last edited by honey bo bo; 04-09-2015 at 09:19 PM. Reason: add on

goubejp · 04-10-2015, 01:50 AM

I have a A*1200 on sale for much less; add a 1,4 X converter and you'll have 1680 mm and better IQ.
Anything above F11 is not useful cause of diffraction anyway

**southlander** · 04-10-2015, 01:51 AM

While I have one or two M lenses, I don't see myself springing for this baby!

K David · 04-10-2015, 10:20 AM

Originally posted by goubejp

Anything above F11 is not useful cause of diffraction anyway

Yes and no. That depends on the lens. f11 on a 50mm lens, as you know, is a lot different than f11 on a 300mm lens. On the 50mm lens, f11 is an aperture opening of 4.54mm. On the 300mm lens, f11 is an aperture opening of 27.27mm. Diffraction is a result of aperture size, so the longer the lens the greater the required f stop before diffraction is an issue. That's one of the reasons why large format photographers can use smaller apertures without image quality loss.

On a 2,000mm lens, the aperture at f13.5 is 148mm across. Even at f32, the aperture is 62.5mm across -- many Pentax lenses could fit through that aperture opening.

**UncleVanya** · 04-10-2015, 06:34 PM

Originally posted by K David

Yes and no. That depends on the lens. f11 on a 50mm lens, as you know, is a lot different than f11 on a 300mm lens. On the 50mm lens, f11 is an aperture opening of 4.54mm. On the 300mm lens, f11 is an aperture opening of 27.27mm. Diffraction is a result of aperture size, so the longer the lens the greater the required f stop before diffraction is an issue. That's one of the reasons why large format photographers can use smaller apertures without image quality loss.

On a 2,000mm lens, the aperture at f13.5 is 148mm across. Even at f32, the aperture is 62.5mm across -- many Pentax lenses could fit through that aperture opening.

Nothing I have ever read on this topic has indicated any dependency on focal length. I'm not saying you are wrong, it is just odd that this is largely glossed over.

This site is typical Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks

---------- Post added 04-10-15 at 09:44 PM ----------

This seems to explicitly refute that focal length is a factor...

Finding the Diffraction Limit - doesn't it depend on focal length and pixel size?

Other discussions point out that print size and viewing distances are integral to this and discounting those factories is misleading.

Glorfindelrb · 04-10-2015, 06:45 PM - **1 Like**

Originally posted by UncleVanya

Nothing I have ever read on this topic has indicated any dependency on focal length. I'm not saying you are wrong, it is just odd that this is largely glossed over.

This site is typical Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks

Your site does answer this.

Quote:

Technical Note: Independence of Focal Length
Since the physical size of an aperture is larger for telephoto lenses (f/4 has a 50mm diameter at 200mm, but only a 25mm diameter at 100mm), why doesn't the airy disk become smaller? This is because longer focal lengths also cause light to travel further before hitting the camera sensor -- thus increasing the distance over which the airy disk can continue to diverge. The competing effects of larger aperture and longer focal length therefore cancel, leaving only the f-number as being important (which describes focal length relative to aperture size).

**UncleVanya** · 04-10-2015, 06:47 PM

Originally posted by Glorfindelrb

Your site does answer this.

Thanks, my question seems answered, focal length isn't a factor.

**monochrome** · 04-10-2015, 09:22 PM

For that money you can buy the FF and all three new D-FA zoom lenses. And the Princesses.

04-09-2015, 07:33 PM	#1
K David Veteran Member Join Date: Oct 2012 Location: Colorado Photos: Gallery Posts: 1,437	2,000mm f13.5 SMC-M on eBay 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. Asahi Pentax SMC M 2000mm F13 5 Reflex Lens Nikon F Adapter for Pentax K \| eBay Not sure if anyone saw this, but if you have $12K to spare, go for it. It's interesting to see some other photos of this lens. I'd love to see what kind of photos it can take. No affiliation with the seller.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
SMC-M 50/1.4 on eBay	RioRico	Pentax Price Watch	3	10-18-2011 04:03 PM
For Sale - Sold: SMC 85mm f/2.2 Soft, SMC-M 50mm f/4 Macro, SMC-M 135 3.5, SMC-M 85mm 2, SMC-M	jgmankos	Sold Items	3	06-14-2010 06:48 PM

04-09-2015, 07:43 PM	#2
calsan Pentaxian Join Date: Nov 2008 Location: Perth, Australia Photos: Gallery Posts: 1,549	Seems a big bunch of money for a mirror lens.

04-09-2015, 07:51 PM	#3
DeadJohn Pentaxian Join Date: Jan 2011 Location: New York Posts: 4,834	Definitely not worth it unless you're a collector. Save $11000 and buy a new 2000mm f10 telescope C8-A XLT (CGE) Optical Tube Assembly [item # 91024-XLT]

04-10-2015, 01:50 AM	#5
goubejp Veteran Member Join Date: Oct 2007 Location: France Photos: Albums Posts: 804	I have a A*1200 on sale for much less; add a 1,4 X converter and you'll have 1680 mm and better IQ. Anything above F11 is not useful cause of diffraction anyway

04-10-2015, 01:51 AM	#6
southlander Site Supporter Join Date: May 2012 Location: Adelaide Photos: Gallery \| Albums Posts: 1,364	While I have one or two M lenses, I don't see myself springing for this baby!

04-10-2015, 10:20 AM	#7
K David Veteran Member Join Date: Oct 2012 Location: Colorado Photos: Gallery Posts: 1,437 Original Poster	Originally posted by goubejp Anything above F11 is not useful cause of diffraction anyway Yes and no. That depends on the lens. f11 on a 50mm lens, as you know, is a lot different than f11 on a 300mm lens. On the 50mm lens, f11 is an aperture opening of 4.54mm. On the 300mm lens, f11 is an aperture opening of 27.27mm. Diffraction is a result of aperture size, so the longer the lens the greater the required f stop before diffraction is an issue. That's one of the reasons why large format photographers can use smaller apertures without image quality loss. On a 2,000mm lens, the aperture at f13.5 is 148mm across. Even at f32, the aperture is 62.5mm across -- many Pentax lenses could fit through that aperture opening.

04-10-2015, 06:34 PM	#8
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,445	Originally posted by K David Yes and no. That depends on the lens. f11 on a 50mm lens, as you know, is a lot different than f11 on a 300mm lens. On the 50mm lens, f11 is an aperture opening of 4.54mm. On the 300mm lens, f11 is an aperture opening of 27.27mm. Diffraction is a result of aperture size, so the longer the lens the greater the required f stop before diffraction is an issue. That's one of the reasons why large format photographers can use smaller apertures without image quality loss. On a 2,000mm lens, the aperture at f13.5 is 148mm across. Even at f32, the aperture is 62.5mm across -- many Pentax lenses could fit through that aperture opening. Nothing I have ever read on this topic has indicated any dependency on focal length. I'm not saying you are wrong, it is just odd that this is largely glossed over. This site is typical Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks ---------- Post added 04-10-15 at 09:44 PM ---------- This seems to explicitly refute that focal length is a factor... Finding the Diffraction Limit - doesn't it depend on focal length and pixel size? Other discussions point out that print size and viewing distances are integral to this and discounting those factories is misleading.

04-10-2015, 06:45 PM - 1 Like	#9
Glorfindelrb Veteran Member Join Date: Feb 2012 Posts: 364	Originally posted by UncleVanya Nothing I have ever read on this topic has indicated any dependency on focal length. I'm not saying you are wrong, it is just odd that this is largely glossed over. This site is typical Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks Your site does answer this. Quote: Technical Note: Independence of Focal Length Since the physical size of an aperture is larger for telephoto lenses (f/4 has a 50mm diameter at 200mm, but only a 25mm diameter at 100mm), why doesn't the airy disk become smaller? This is because longer focal lengths also cause light to travel further before hitting the camera sensor -- thus increasing the distance over which the airy disk can continue to diverge. The competing effects of larger aperture and longer focal length therefore cancel, leaving only the f-number as being important (which describes focal length relative to aperture size).

04-10-2015, 06:47 PM	#10
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,445	Originally posted by Glorfindelrb Your site does answer this. Thanks, my question seems answered, focal length isn't a factor.

04-10-2015, 09:22 PM	#11
monochrome Loyal Site Supporter Join Date: Mar 2008 Location: Working From Home Photos: Gallery \| Albums Posts: 26,276	For that money you can buy the FF and all three new D-FA zoom lenses. And the Princesses.