Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
08-28-2012, 02:55 PM   #1
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
Macro: edge quality - tubes vs achromat diopter

I'm having a heated discussion with someone on dpreview who insists that, for non-macro lenses, good diopter add-on close-up lenses give better edge/corner results than do Bellows/tubes at less than 1:1 mag.

I'm seeking evidence this might be true. All my tests show it the other way 'round: extension gives better edge/corner quality than do diopter achromats.

I've tested Raynox 150, Nikon 4T, Marumi +5. all show bad contrast and softness in corners with moderate quality lens (Pentax A 50:2)

Please let me know of evidence (ie. actual photos, measurements, or authoritative sources) one way or the other.

Thanks,
Dave

REF: close-up lens' versus extension tubes [Page 1]: Open Talk Forum: Digital Photography Review

08-28-2012, 04:29 PM   #2
Moderator
Not a Number's Avatar

Join Date: Mar 2012
Location: Venice, CA
Posts: 7,455
Macro Comparison
08-28-2012, 05:26 PM   #3
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 16,235
Logically, unless an add on diopter is specifically designed for only one lens and it's aborations it is unlikely that edge sharpness wold improve with the diopter over the lens itself. Tubes are the way to go. Add on diopters only advantage is that they shorten the focal length while leaving the aperture diameter unchanged, and therefore thenFNumber goes down (lens gets faster)
08-28-2012, 07:11 PM   #4
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
Original Poster
QuoteOriginally posted by Not a Number Quote
Thank you. That's the person I'm conversing with and the only evidence I've seen. I've no reason to doubt the results for that test but have seen no other hard evidence.

Dave

08-28-2012, 07:40 PM   #5
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 5,392
I think it just depends on the combo -- did you test the Pentax 50/2 (kind of a crappy lens) with tubes also?
08-28-2012, 09:06 PM   #6
Inactive Account




Join Date: Dec 2008
Location: North Carolina
Photos: Albums
Posts: 1,720
QuoteOriginally posted by vonBaloney Quote
I think it just depends on the combo
It really does, some lenses work better on extension tubes than others, just like some lenses work better with certain diopters than others. Without trying every possible combination, it is impossible to know what will work best with what. Just find a setup that works for you, experiment with reverse mounting lenses and enlarger lenses too, there are many ways to achieve macro focus.

That site showing the test is terribly flawed, mostly because he didn't even use the same lens. I understand that he didn't have extension tubes to use with the Minolta AF lens, but he couldn't even be bothered to put the diopter on the Rokkor. He just proved the Minolta AF with a diopter is better than a Rokkor with an extension tube, which is useless. To definitively prove anything, you need a variety of lenses each tested with the extension tube and diopter, even then you might not prove anything.
08-29-2012, 08:50 AM   #7
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
Original Poster
Normal lenses expect parallel light when focused at infinity. Diopter type close-up lenses put the subject at infinity (in effect) This should make for a pretty good image - at least in the center.

Behavior at corners/edges should be less predictable. I used the A 50:2 for testing because it isn't stellar lens and I didn't want to bias the test towards special lenses.

I'm still seeking more comparison examples that show one effect or the other!

Thanks for your contributions thus far.

Dave
08-29-2012, 09:50 AM   #8
Pentaxian
audiobomber's Avatar

Join Date: May 2008
Location: Sudbury, Ontario
Photos: Albums
Posts: 6,801
Here's what I would do: Shoot a ruler with a 100mm macro at 1:1. Shoot with the same lens and a Raynox 150 mounted, adjust focus so that it gives 1.2:1. Remove the Raynox, mount a 25mm adapter for 1.2:1 macro at minimum focus. Crop the image from the bare lens to 1.2:1 as a control. Check the others for deterioration. I may do this, because I'm still a little confused about effective apertures with a macro lens vs diopter vs .

08-29-2012, 10:35 AM   #9
Veteran Member
westmill's Avatar

Join Date: Jan 2012
Location: Stoke on Trent
Photos: Gallery | Albums
Posts: 1,146
You lose X amount of quality just by fitting a good quality filter !!!!! Bellows and tubes do not have glass ! Of course you will get higher quality from bellows or tubes.
08-29-2012, 10:58 AM   #10
Pentaxian
audiobomber's Avatar

Join Date: May 2008
Location: Sudbury, Ontario
Photos: Albums
Posts: 6,801
QuoteOriginally posted by westmill Quote
You lose X amount of quality just by fitting a good quality filter !!!!! Bellows and tubes do not have glass ! Of course you will get higher quality from bellows or tubes.
I don't think your argument will convince the guy that Dave is arguing with. He needs proof..
08-29-2012, 11:17 AM   #11
Veteran Member
westmill's Avatar

Join Date: Jan 2012
Location: Stoke on Trent
Photos: Gallery | Albums
Posts: 1,146
QuoteOriginally posted by audiobomber Quote
I don't think your argument will convince the guy that Dave is arguing with. He needs proof..
True lol... mmmmm personly i would just ignore him
08-29-2012, 01:23 PM   #12
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
Original Poster
QuoteOriginally posted by westmill Quote
True lol... mmmmm personly i would just ignore him
I'd like evidence not only because his clever writing made me look silly if not stupid, but also because I really want to know.

I'd hate to have his clever writing mislead a lot of folks. It looks to me like there is no certain answer.
08-29-2012, 01:40 PM   #13
Veteran Member
westmill's Avatar

Join Date: Jan 2012
Location: Stoke on Trent
Photos: Gallery | Albums
Posts: 1,146
QuoteOriginally posted by newarts Quote
I'd like evidence not only because his clever writing made me look silly if not stupid, but also because I really want to know.

I'd hate to have his clever writing mislead a lot of folks. It looks to me like there is no certain answer.
I can understand that. there are those that are so good with words they can convince people black is white lol. Then you get those that understand all the maths and quote pages of info at you but they still miss the end result even though they are very knowledgeable. They think they understand it but they add 2 and 2 and create 5. With these people, it is rare you will open there eyes. It is not worth losing sleep over. I do understand the frustration though. If you have one of these types, trust me, whatever evidence you find will not be enough. Its kind of why I have people on my ignore list lol. Its no use knocking when there is no one home
08-29-2012, 03:01 PM   #14
Pentaxian
amoringello's Avatar

Join Date: May 2008
Location: Virginia, USA
Photos: Gallery
Posts: 1,562
he, he, I have not used tubes yet, but I don't see how an extension tube can give the added aberration in his bottom-most image unless it is bent.
He went from an image that is decent edge to edge quality to one that has warped at the edge.

Someone let me know if I'm wrong here (again I don't have tubes to test and can only think logically about their function), but...
An extension tube is in effect doing the same as a crop sensor does when used with a full frame lens (not exactly, but similar principles). It is enlarging the image circle onto your sensor to that the sensor is taking only a portion from the center of your image circle. So if anything, it is magnifying the best part of the image created by the lens -- that which avoids edge deterioration. With a lens tube, the edges should be potentially sharper than with the original lens on its own. Now to note, you are enlarging the image circle, so any imperfections in the glass will be magnified and that might render a softer image. I could see that the result might be a less sharp image, but such distortion simply does not make sense.
Am I off my rock here?

Anyway, I agree with the others... never fight a troll.
No matter how hard you hit them, they will regenerate and are just too stupid to stop fighting.
08-29-2012, 03:24 PM   #15
Pentaxian
audiobomber's Avatar

Join Date: May 2008
Location: Sudbury, Ontario
Photos: Albums
Posts: 6,801
QuoteOriginally posted by amoringello Quote
he, he, I have not used tubes yet, but I don't see how an extension tube can give the added aberration in his bottom-most image unless it is bent.
He went from an image that is decent edge to edge quality to one that has warped at the edge.
Note that he used different lenses, which completely invalidates his results. I suspect the second lens is decentered or somehow defective.
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!
close-up, diopter, evidence, extension, lens, lenses, quality, tripod, tubes
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: H.Q. 2.5 diopter achromat: Olympus IS/L A-Macro (Worldwide) cheekygeek Sold Items 2 07-04-2011 12:43 PM
For Sale - Sold: COSINA 100mm 3.5 MACRO with 1:1 ACHROMAt pentmax Sold Items 6 03-19-2011 12:38 PM
Zoom Lens into Macro using close up diopter? Gsmp Pentax SLR Lens Discussion 5 03-03-2011 10:20 PM
Basic question regarding image circle and edge quality tigershoot Pentax SLR Lens Discussion 3 01-27-2009 02:56 PM
Living on the edge (macro) mikerigel Post Your Photos! 13 07-16-2007 08:28 AM



All times are GMT -7. The time now is 01:26 AM. | 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