Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-30-2021, 05:35 PM   #1
Closed Account
Michael Piziak's Avatar

Join Date: Dec 2013
Location: West Virginia
Posts: 2,815
How many extension tubes can one use - ?

How many extension tubes, or mm of extension tubes, can one use before you either get to close to the subject or light degrades too much or something else degrades - ??

My pic today using the Asahi Pentax m-100mm macro f4 with Asahi Pentax extension tubes (57mm total tubes)



03-30-2021, 06:00 PM   #2
Loyal Site Supporter
Loyal Site Supporter




Join Date: Oct 2018
Location: Quebec City, Quebec
Posts: 6,493
Nothing limiting the extension, really. Of course you have to compensate your exposure according to the magnification ratio and get enough DOF the be able to recognize a subject. Inanimate subjects can be magnified easily to 5X or more. You can add extension tubes to a set of bellows (here the 645 Auto Bellows with 645 #2 Extension Tube and '645 to K' adapter with a 645 A 75 mm f/2.8 normal lens). The K3 compensated for the light loss and exposed automatically in Av mode. The shorter the lens, the greater a magnification you can achieve.



03-30-2021, 06:10 PM   #3
Site Supporter
Site Supporter




Join Date: Jun 2008
Location: Terrace, BC, Canada
Photos: Albums
Posts: 122
If you are using automatic tubes that close down the aperture when you make the shot, you'll hit a mechanical limit where the linkages cannot perform their function. You are using three tubes? You might get another one or two.
When you use too much extension you can also reach a point where the plane of focus is so close that it is now inside the lens.
03-30-2021, 06:10 PM   #4
Closed Account
Michael Piziak's Avatar

Join Date: Dec 2013
Location: West Virginia
Posts: 2,815
Original Poster
QuoteOriginally posted by RICHARD L. Quote
Nothing limiting the extension, really. Of course you have to compensate your exposure according to the magnification ratio and get enough DOF the be able to recognize a subject. Inanimate subjects can be magnified easily to 5X or more. You can add extension tubes to a set of bellows (here the 645 Auto Bellows with 645 #2 Extension Tube and '645 to K' adapter with a 645 A 75 mm f/2.8 normal lens). The K3 compensated for the light loss and exposed automatically in Av mode. The shorter the lens, the greater a magnification you can achieve.



Outstanding photo - is that blueberries?

Interesting. I have the m100mm macro lens and ordered the m50mm macro lens. So, I can actually get more magnification if using the shorter 50mm macro lens (with extension tubes) ?

---------- Post added 03-30-21 at 06:15 PM ----------

QuoteOriginally posted by Derek Quote
If you are using automatic tubes that close down the aperture when you make the shot, you'll hit a mechanical limit where the linkages cannot perform their function. You are using three tubes? You might get another one or two.
When you use too much extension you can also reach a point where the plane of focus is so close that it is now inside the lens.
I'm pretty sure I'm using the old non-automatic Asahi Pentax extension tubes. I use the green button for Tv shift.
Thanks for your reply - I understand.

Addendum: I think I might have the auto extension tubes - they're the ones like here: https://www.pentaxforums.com/articles/influential-gear/asahi-pentax-auto-extension-tubes.html But regardless, I'm using the M macro lens where I select the aperture on the lens. I really don't know if the tubes are doing something to the lens (aperture?) when I use the green button (for Tv shift) - ???


Last edited by Michael Piziak; 03-30-2021 at 06:21 PM.
03-30-2021, 06:20 PM   #5
Loyal Site Supporter
Loyal Site Supporter




Join Date: Oct 2018
Location: Quebec City, Quebec
Posts: 6,493
Quebec blueberries indeed. One blueberry to a pie ... lol !

A shorter 50 mm Macro will get you very close to the subject (a few inches), so it might scare away insects and the like plus it may create shadows or make lighting more difficult. A 100 mm Macro will get the same magnification (typically 1:2 or 1:1) but at a greater 'subject to lens' distance and will achieve a slightly different perspective. The same Extension Tube will amplify magnification 2 times more on a 50 than on a 100 mm lens. It is also true extreme extension may create linkage problems for automatic tubes. Older A series 50 mm Macro achieved only 1:2 (0.5 X) magnification while a more modern DFA 100 mm f/2.8 goes to 1:1 unaided, if I'm right. Better check this in the 'Lens Reviews' section of the Forum.

Regards

Last edited by RICHARD L.; 03-30-2021 at 06:30 PM.
03-30-2021, 06:28 PM   #6
Site Supporter
Site Supporter
AggieDad's Avatar

Join Date: Jan 2015
Location: Houston, TX
Photos: Gallery | Albums
Posts: 1,440
QuoteOriginally posted by Michael Piziak Quote
How many extension tubes, or mm of extension tubes, can one use before you either get to close to the subject or light degrades too much or something else degrades - ??
How many do you have?

Seriously, just make sure you have some support for them if really start stacking them. A better bet might be to find a bellows to use. My Pentax bellows adjusts from about 3.5 to 16 cm – and I can add an extension tube or two on to it if I want.
03-30-2021, 06:39 PM   #7
Closed Account
Michael Piziak's Avatar

Join Date: Dec 2013
Location: West Virginia
Posts: 2,815
Original Poster
QuoteOriginally posted by AggieDad Quote
How many do you have?

Seriously, just make sure you have some support for them if really start stacking them. A better bet might be to find a bellows to use. My Pentax bellows adjusts from about 3.5 to 16 cm – and I can add an extension tube or two on to it if I want.
Well, I just have the Asahi Pentax extension tubes 1,2, & 3 (totalling 57mm of tubes).
I was just playing around in my head and thinking if I bought another set and played around with adding a tube or 2, then what would happen.
Oh, & I do most all my shooting, hand held, in the field - so adding too many could become a problem - lol

03-30-2021, 07:13 PM - 1 Like   #8
Site Supporter
Site Supporter
gofour3's Avatar

Join Date: Oct 2008
Location: Vancouver, Canada
Posts: 8,085
QuoteOriginally posted by Michael Piziak Quote
Well, I just have the Asahi Pentax extension tubes 1,2, & 3 (totalling 57mm of tubes).
I was just playing around in my head and thinking if I bought another set and played around with adding a tube or 2, then what would happen.
Oh, & I do most all my shooting, hand held, in the field - so adding too many could become a problem - lol
You would be better off reversing a lens and using a bellows unit, than a stack of extension tubes. 28mm lenses are good for reversing with higher magnification.

Phil.
03-30-2021, 07:45 PM   #9
Pentaxian
swanlefitte's Avatar

Join Date: May 2015
Location: Minneapolis
Photos: Gallery
Posts: 4,068
as to too close I tried with the sigma 10-20mm. I only used the collars of the tubes and by 10mm it was too close. If I remember correctly the object touched at 14mm and at 10mm the subject would need to be in the lens.
03-30-2021, 07:58 PM   #10
Closed Account
Michael Piziak's Avatar

Join Date: Dec 2013
Location: West Virginia
Posts: 2,815
Original Poster
QuoteOriginally posted by gofour3 Quote
You would be better off reversing a lens and using a bellows unit, than a stack of extension tubes. 28mm lenses are good for reversing with higher magnification.

Phil.
Thanks for the reply.
But yea, I do much of my macros in the field - it's a non-bellows situation. I suspect I could add another #1 tube anyways....

---------- Post added 03-30-21 at 08:00 PM ----------

QuoteOriginally posted by swanlefitte Quote
as to too close I tried with the sigma 10-20mm. I only used the collars of the tubes and by 10mm it was too close. If I remember correctly the object touched at 14mm and at 10mm the subject would need to be in the lens.
Thanks for the reply.
I think my 2 lens would be more accomodating to adding an extra #1 tube or perhaps even another #2 tube - ?
Again, my lens are the Asahi Pentax m-100mm macro f4 and Asahi Pentax m-50mm macro f4
(on a k-s2)
03-30-2021, 08:25 PM   #11
Otis Memorial Pentaxian
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 42,007
QuoteOriginally posted by Michael Piziak Quote
Interesting. I have the m100mm macro lens and ordered the m50mm macro lens. So, I can actually get more magnification if using the shorter 50mm macro lens (with extension tubes) ?
Less working distance...much less.


Steve
03-31-2021, 08:02 AM   #12
Pentaxian
photoptimist's Avatar

Join Date: Jul 2016
Photos: Albums
Posts: 5,113
100mm of extension on a 100 mm f/4 lens gets you 1:1 magnification but knocks two stops off the aperture (f/8 with the lens wide open).

300mm of extension on a 100 mm f/4 lens gets you 3:1 magnification but knocks four stops off the aperture (f/16 with the lens wide open).

700mm of extension on a 100 mm f/4 lens gets you 7:1 magnification but knocks six stops off the aperture (f/32 with the lens wide open).


A 50mm lens will get these magnifications and light-loss levels with 50, 150, and 350 mm of extension. That is, you get twice the magnification for a given amount of extension. However, a given amount of magnification creates a given amount of light loss regardless of focal length.


P.S. macro lenses typically have a long throw on the focus range which gives them up to 1/2 to a full focal length worth of extension in addition to the tubes.

P.P.S. Diffraction starts to be a detail-killer at higher magnifications which, combined with being forced to use the lens wide open can mean that sharp pictures are impossible.

P.P.P.S. Hand-holding at high magnifications is also unlikely to work well. SR doesn't work at high magnifications (in theory, it could, but in practice the SR system would need to know the magnification factor which it doesn't so SR doesn' know how to stabilize extreme macro shooting scenarios).
03-31-2021, 08:10 AM   #13
Closed Account
Michael Piziak's Avatar

Join Date: Dec 2013
Location: West Virginia
Posts: 2,815
Original Poster
QuoteOriginally posted by photoptimist Quote
100mm of extension on a 100 mm f/4 lens gets you 1:1 magnification but knocks two stops off the aperture (f/8 with the lens wide open).

300mm of extension on a 100 mm f/4 lens gets you 3:1 magnification but knocks four stops off the aperture (f/16 with the lens wide open).

700mm of extension on a 100 mm f/4 lens gets you 7:1 magnification but knocks six stops off the aperture (f/32 with the lens wide open).


A 50mm lens will get these magnifications and light-loss levels with 50, 150, and 350 mm of extension. That is, you get twice the magnification for a given amount of extension. However, a given amount of magnification creates a given amount of light loss regardless of focal length.


P.S. macro lenses typically have a long throw on the focus range which gives them up to 1/2 to a full focal length worth of extension in addition to the tubes.

P.P.S. Diffraction starts to be a detail-killer at higher magnifications which, combined with being forced to use the lens wide open can mean that sharp pictures are impossible.

P.P.P.S. Hand-holding at high magnifications is also unlikely to work well. SR doesn't work at high magnifications (in theory, it could, but in practice the SR system would need to know the magnification factor which it doesn't so SR doesn' know how to stabilize extreme macro shooting scenarios).
Thanks for the reply. So this confirms that using a 50mm macro lens with extension tubes, that I've ordered, will get more magnification than my current 100mm macro - very interesting. You are the 2nd person that posted this, so I believe it.

Concerning 1:1 macro. My only grounds for questioning your calculations, is that in another thread, a user told me that one only needs 50mm of extension tubes, on a 100mm macro lens, to get 1:1 magnification. But perhaps the APS-C sensor size is the reason for this - ?
03-31-2021, 08:46 AM   #14
Site Supporter
Site Supporter




Join Date: Jun 2008
Location: Idaho
Photos: Gallery
Posts: 2,360
QuoteOriginally posted by Michael Piziak Quote
....................Concerning 1:1 macro. My only grounds for questioning your calculations, is that in another thread, a user told me that one only needs 50mm of extension tubes, on a 100mm macro lens, to get 1:1 magnification. But perhaps the APS-C sensor size is the reason for this - ?
You get 1:1 magnification on any lens when the lens-to-subject and the lens-to-sensor (or film) are both twice the infinity focal length (that which is normally listed for a lens). On a 100mm lens, the lens-to-sensor distance would be 200mm for 1:1. The macro lens itself will provide some of that (actually all of that if it's capable of 1:1 on its own), but if left at the infinity setting, 100mm already exists so a 100mm extension is needed. If you make use of the macro lens close focusing abilities, less than 100mm may be needed.

1:1 magnification is irrelevant of sensor size and simply means the image on the sensor is the same size as the subject. This happens when subject and sensor distances from the lens are equal.
03-31-2021, 11:05 AM   #15
Site Supporter
Site Supporter




Join Date: Jun 2008
Location: Terrace, BC, Canada
Photos: Albums
Posts: 122
Another approach would be a cheap 49mm lens coupler from ebay. Mount your 100 on the camera and then reverse mount the 50 to that to take you to 2:1. You're using the 50 as a close-up filter, but there's not much room between you and your subject. Hand-held becomes really only possible with macro flash.
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!
10mm, asahi, degrades, extension, extension tubes, f4, k-mount, lens, macro, magnification, pentax, pentax lens, reply, slr lens, thanks, tube, tubes
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Question: Can you use extension tubes with the 100mm macrof2.8 D-FA (Water resistant) stemked Pentax SLR Lens Discussion 9 02-17-2021 02:21 PM
Wanted - Acquired: K Mount extension tubes, and / or Helicoid extension tube gsrokmix Sold Items 2 01-15-2021 08:48 PM
How many is too many (how many is too few)? hooverfocus Photographic Industry and Professionals 14 04-05-2017 02:38 PM
Confused - How to (can you) use DA 35mm with extension tubes? ohaya Troubleshooting and Beginner Help 48 02-19-2016 01:50 PM



All times are GMT -7. The time now is 09:49 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