Re: lens of the week: 2000/13.5 and M 2000/13.5
From: Bojidar Dimitrov [EMAIL PROTECTED] Hi, a question to the optical-formula gurus. Pentax describes the optics of this mirror lens as 6 elements in 4 groups. Looking at the diagram that they provide us, I see 8 elements. I will number them 1 through 8 when looking from left to right. 1 and 2 as well as 5 and 6 seem to be forming the two two-element groups (like the optical formula suggests), but what about the rest? I am thinking like this: - elements 2 and 3 must be mirrors, so they might not be counted towards the number of optical elements. Now we are down to 6 elements which agrees with Pentax. But the number of groups is now 5. - alternatively, element 8 is the screw-on filter, so that might not be counted. Then we are left with 7-5. Still doesn's fit. Your ideas are welcome. Cheers, Boz Boz, my interpretation : first group of 2 elements, some schmidt/maksutov like corrector forms a group with the secundary mirror. Second group of 1 element is the primary mirror (maybe mangin mirror?) light goes then to the already mentioned secondary mirror, and then back to the third group af 1 element, a negative lens. Then the 2 element fourth group, some kitted achromat. So, now we have 4 groups and 6 elements, although I have my doubts if it is right to consider the corrector/secondary mirror one group. The last 2 elements, are the 2 filterwheels. one for the color filters, and one for the ND filters Probably not counted as elements. George - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
RE: lens of the week: 2000/13.5 and M 2000/13.5
Just make sure the focus is set properly when you see Prince Charles, Britney Spears and Boy George having a threesome in Buckingham Palace with the curtains wide open :) Is there anybody that actually owns one of these? I often though of getting one and starting up my on little domestic spy business. You could do some neat things with it and some 3200 ASA BW film! __ Do You Yahoo!? Yahoo! Auctions - buy the things you want at great prices http://auctions.yahoo.com/ - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
Re: lens of the week: 2000/13.5 and M 2000/13.5
Hi, a question to the optical-formula gurus. Pentax describes the optics of this mirror lens as 6 elements in 4 groups. Looking at the diagram that they provide us, I see 8 elements. I will number them 1 through 8 when looking from left to right. 1 and 2 as well as 5 and 6 seem to be forming the two two-element groups (like the optical formula suggests), but what about the rest? I am thinking like this: - elements 2 and 3 must be mirrors, so they might not be counted towards the number of optical elements. Now we are down to 6 elements which agrees with Pentax. But the number of groups is now 5. - alternatively, element 8 is the screw-on filter, so that might not be counted. Then we are left with 7-5. Still doesn's fit. Your ideas are welcome. Cheers, Boz - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
Re: lens of the week: 2000/13.5 and M 2000/13.5
Hello, about this lense, how good would this make a LX with SD-11 clear for astrophotopgrahy ? equivalent of this would be 5.8" mirror Smith Cassegrain. and a 24x36mm eye-piece... what type of TC could be used with this lense ? Philippe Hi, a question to the optical-formula gurus. Pentax describes the optics of this mirror lens as 6 elements in 4 groups. Looking at the diagram that they provide us, I see 8 elements. I will number them 1 through 8 when looking from left to right. 1 and 2 as well as 5 and 6 seem to be forming the two two-element groups (like the optical formula suggests), but what about the rest? I am thinking like this: - elements 2 and 3 must be mirrors, so they might not be counted towards the number of optical elements. Now we are down to 6 elements which agrees with Pentax. But the number of groups is now 5. - alternatively, element 8 is the screw-on filter, so that might not be counted. Then we are left with 7-5. Still doesn's fit. Your ideas are welcome. Cheers, Boz - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org . - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
Re: lens of the week: 2000/13.5 and M 2000/13.5
William wrote: Is there anybody that actually owns one of these? I often though of getting one and starting up my on little domestic spy business. You could do some neat things with it and some 3200 ASA BW film! If you can focus it! I had troubles with the 1000/11. Try to stop down any lens to F:11 and try focusing it. A 2000mm will be 10 times worse; remeber the focusing accuracy involved. Its pretty much hopeless in my experience. Focusing bracketing is mandatory. Pl - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
Re: lens of the week: 2000/13.5 and M 2000/13.5
on 4/19/01 11:16 AM, O'Neill, William at William.O'[EMAIL PROTECTED] wrote: Is there anybody that actually owns one of these? I often though of getting one and starting up my on little domestic spy business. You could do some neat things with it and some 3200 ASA BW film! - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org . - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
RE: lens of the week: 2000/13.5 and M 2000/13.5
Pl said: If you can focus it! I had troubles with the 1000/11. Try to stop down any lens to F:11 and try focusing it. A 2000mm will be 10 times worse; remeber the focusing accuracy involved. Its pretty much hopeless in my experience. Focusing bracketing is mandatory. I say: Yes, but Pl, in the domestic spy business, all you need to do is be able to recognize the guy/gal cavorting with the other guy/gal. Wall hanging quality isn't such an issue for most of the clients. - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
