Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
06-27-2013, 09:48 PM - 4 Likes   #1
Veteran Member
scratchpaddy's Avatar

Join Date: Feb 2013
Location: Phoenix
Posts: 2,360
The TP Special!

This morning, I woke up with an idea in my head: how about making a single-element lens, a lens that is literally just one lens? It should work. Every converging lens has a focal point; just put the lens at the right distance from the sensor, and you have a camera! Who needs all those other elements, anyway?

I have an old fungus-infected JCPenney zoom that came in a lot from eBay. It was 8 lenses, including a Kiron 70-210 f/4, which is a fine lens. It must have gotten overlooked, because I was the only bidder at $10.

Lucky for me, the crappy JCPenney was the only one with fungus. I didn't mind taking it apart for this little experiment.

I got to it as soon as I got home from work. It's not like there's much else to do when it's 110 outside.

To keep most of the light from getting to the sensor from around the lens, I needed a tube. I used two toilet paper tubes, since they were available. I had to crimp one down a bit so it would fit inside the other. I could use the sliding action between the two for a focus mechanism. I used scotch tape to get the lens onto the tube, and it was done! The TP Special: a real piece of precision optical engineering.



There was still some room for stray light to get into the mirror box, but whatever. This is just a prototype.

It's a shame I got the lens from a telephoto. It's a little clumsy to work with something so long. I think the focal length of this lens is about 200mm, but I don't have anything laying around to measure it with. And I call myself an engineer. This is unacceptable!

This was the first shot I got. Only the overexposed background was in focus, but it had lots of pretty colors.




Maybe they put all those elements in lenses to get some detail in places other than the exact center of the photo?




I showed it to my dog, but she was unimpressed.




Sharpness is obviously not this lens's strong suit. Horses for courses, I say. Use it to capture all that optical mess you never see with all those other elements correcting for it.




This is my favorite so far. You can see the whole spectrum on the edges of the leaves with the brightest backlight.




Not bad for toilet paper, eh?

06-27-2013, 10:01 PM   #2
Junior Member




Join Date: May 2013
Location: Dillon Colorado
Posts: 31
This may be the coolest use of a toilet paper roll ever! Did you just happen to have an empty one laying around or did you have to empty it in the name of science?
06-27-2013, 10:18 PM   #3
Veteran Member
scratchpaddy's Avatar

Join Date: Feb 2013
Location: Phoenix
Posts: 2,360
Original Poster
QuoteOriginally posted by Johnyb3000 Quote
This may be the coolest use of a toilet paper roll ever! Did you just happen to have an empty one laying around or did you have to empty it in the name of science?
I just happened to finish a roll of toilet paper and paper towels in the same day. It was a fortunate coincidence. I'd hate to be wasteful, but I'd do most anything in the name of science!

It's too bad Skippy doesn't appreciate it as much as you do. Dogs just don't have much interest in science, it seems... or maybe she's just tired of having lenses tested on her?
06-27-2013, 10:42 PM   #4
Site Supporter
Tako Kichi's Avatar

Join Date: May 2013
Location: SW Ontario, Canada (ex-pat Brit)
Posts: 1,067
Ya know if you got some caulking you could use it to seal up those gaps between the tube and the camera. Might make swapping lenses a tad difficult though.

06-28-2013, 05:03 AM   #5
Pentaxian
panoguy's Avatar

Join Date: Sep 2007
Location: Washington, D.C.
Photos: Gallery | Albums
Posts: 3,290
Nice!
I think Tamron made a TP-PK Adaptall mount... didn't they?
06-28-2013, 05:14 AM   #6
Pentaxian
bdery's Avatar

Join Date: Mar 2008
Location: Quebec city, Canada
Photos: Gallery
Posts: 5,798
This is pretty cool, in a back-to-basics kind of way. Contrats on the funny narrative!
06-28-2013, 05:56 AM   #7
Pentaxian




Join Date: Nov 2011
Photos: Gallery | Albums
Posts: 3,723
PRIC will be miffed to hear that their 07 Mount Shield lens is no longer the worst.
06-28-2013, 09:56 AM   #8
Site Supporter




Join Date: Nov 2012
Location: Saint Paul
Posts: 304
Yeah! the dog does look dreamy!!

Edit: Hey I like that radio behind the camera :-)


Last edited by TropicalMonkey; 06-28-2013 at 10:01 AM.
06-28-2013, 10:14 AM   #9
Veteran Member
scratchpaddy's Avatar

Join Date: Feb 2013
Location: Phoenix
Posts: 2,360
Original Poster
QuoteOriginally posted by Tako Kichi Quote
Ya know if you got some caulking you could use it to seal up those gaps between the tube and the camera. Might make swapping lenses a tad difficult though.
You know, I thought about cannibalizing the K-mount from another worthless lens, and then using some sort of rubber tube to connect it to the lens, but somebody already did that, and they called it a Lensbaby.

I might try just gutting all those superfluous elements from the JCPenney, but that wouldn't have that same special "kludge" quality.

QuoteOriginally posted by panoguy Quote
Nice!
I think Tamron made a TP-PK Adaptall mount... didn't they?
Maybe so, but I'm afraid it might involve epoxy, like Larry said.

QuoteOriginally posted by bdery Quote
This is pretty cool, in a back-to-basics kind of way. Contrats on the funny narrative!
Thanks! There's no logical reason to do this, but that "back-to-basics" feel gives me the warm and fuzzies. It's a learning experience, too. Science!

QuoteOriginally posted by lytrytyr Quote
PRIC will be miffed to hear that their 07 Mount Shield lens is no longer the worst.
Shhhhh! You'll hurt its feelings.

QuoteOriginally posted by TropicalMonkey Quote
Yeah! the dog does look dreamy!!

Edit: Hey I like that radio behind the camera :-)
That's the "are you done, yet?" look.

I like that radio, too. That's my favorite thrift store find, ever!
06-29-2013, 04:20 PM   #10
Veteran Member
VisualDarkness's Avatar

Join Date: Nov 2011
Location: Uppsala, Sweden
Photos: Gallery
Posts: 4,441
Hey Paddy!
What about going for a TP photowalk? Too bad we are so far apart.
https://www.pentaxforums.com/forums/pentax-q/226445-ugliest-macro-setup-around-q.html
06-29-2013, 05:29 PM   #11
Veteran Member
scratchpaddy's Avatar

Join Date: Feb 2013
Location: Phoenix
Posts: 2,360
Original Poster
QuoteOriginally posted by VisualDarkness Quote
Hey Paddy!
What about going for a TP photowalk? Too bad we are so far apart.
https://www.pentaxforums.com/forums/pentax-q/226445-ugliest-macro-setup-around-q.html
We should start a TP Club! Cardboard tubes unite!

I've been meaning to do something like this ever since I saw that awesome setup of yours, and TropicalMonkey's question about single element lenses gave me the push I needed. Thanks for the inspiration.

I would love for this lens to get out more, but I worry about dust... and gravity.
06-29-2013, 06:20 PM - 1 Like   #12
Pentaxian
c.a.m's Avatar

Join Date: Jan 2013
Location: Ottawa, Canada
Posts: 1,044
Do you have plans to produce a WR version?
06-29-2013, 08:49 PM   #13
Veteran Member
sam-joseph's Avatar

Join Date: Oct 2009
Location: Newcastle, NSW, Australia
Photos: Gallery
Posts: 1,086
Bit of a crappy job, isn't it? Normally this kind of lens would be used with an open aperture....Do you notice any purple fringing with this one, or is it a different colour?...
I bet the wide-angle version is big, but....
Ok, I'll stop now.

Regards
06-29-2013, 10:21 PM   #14
Veteran Member
scratchpaddy's Avatar

Join Date: Feb 2013
Location: Phoenix
Posts: 2,360
Original Poster
QuoteOriginally posted by c.a.m Quote
Do you have plans to produce a WR version?
What, this isn't resistant enough for you? It resists the weather for a short while before... melting.

Then you make a new one!

QuoteOriginally posted by sam-joseph Quote
Bit of a crappy job, isn't it? Normally this kind of lens would be used with an open aperture....Do you notice any purple fringing with this one, or is it a different colour?...
I bet the wide-angle version is big, but....
Ok, I'll stop now.
Speaking of apertures, this one's got quite an unusual shape. It makes the highlights a bit wonky.



Considering fringing, was there a particular color you had in mind? We've got red, green, yellow, blue, purple... any color you like! Actually, if you wanted something besides fringing, you're flat outta luck.



I'm afraid there won't be a wide-angle version. Without a retrofocal group, I can't get any wider than the K-mount's FFD, which is 45mm.
06-30-2013, 12:49 AM   #15
Site Supporter
Jean Poitiers's Avatar

Join Date: Apr 2011
Location: Lost in translation ...
Photos: Gallery | Albums
Posts: 16,502
The dog "capture" is the best ... J
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
elements, focus, jcpenney, k-mount, lens, lenses, paper, pentax lens, sensor, slr lens, toilet, tp, tube
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Nature Two for one special with the Bigma. charliezap Post Your Photos! 15 01-25-2013 12:38 PM
I bought the Nikon J1 (Pink Special Edition) Christine Tham Non-Pentax Cameras: Canon, Nikon, etc. 23 04-20-2012 02:15 AM
never knew abouts the 43mm 'L special for LEICA' chaza01 Pentax SLR Lens Discussion 5 04-16-2012 05:43 PM
TP asks businesses not to hire Lex Madera General Talk 7 10-25-2011 11:42 AM
special time with a special lens (larger images) Marc Langille Post Your Photos! 30 11-01-2008 09:38 AM



All times are GMT -7. The time now is 02:22 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top