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gearsNcogs
Joined: 20 Oct 2010 Posts: 215
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Posted: Wed Apr 27, 2011 2:09 am Post subject: How do Extender Tubes work? |
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gearsNcogs wrote:
Are they better, worse, or just different from macro lenses? i also just dont understand how they work exactly. _________________ Stills: SLR: Asahi Pentax Spotmatic SP, DSLR: Canon EOS Rebel XTi, Canon EOS 7D
Cine: 16mm: Krasnogorsk-3 (M42 mount) 8mm: Revere Model 88 Super 8: Bell and Howell 1235 XL Filmosonic
MF Lenses: M42: Meteor 5-1 KMZ 17-69mm 1:1,9 (Cine Only), Asahi Super Takumar 50mm 1:1.4, Focal MC 28mm 1:2.8, Tele-Lentar 135mm 1:2.8, Helios-44 KMZ 58mm 1:2, Helios-44-2 KMZ 58mm 1:2 M39: Industar-26M 50mm 1:2.8 F: Nikon Nikkor 50mm 1:1.8 EF: Lensbaby Composer f2 w/Double Glass Optic, Rokinon 35mm 1:1.4 AS UMC, Rokinon 85mm T1.5 AS IF UMC
AF Lenses: EF-S: Canon EF-S 18-55mm 1:3.5-5.6 II, EF: Tamron AF 70-300mm 1:4-5.6 TELE-MACRO (1:2), Canon EF 50mm 1:1.8 II
Fixed-Focus Lenses: D: Elitar 6.5mm 1:1.9, Wollensak-Revere 13mm 1:2.5 Velostigmat |
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RioRico
Joined: 12 Mar 2010 Posts: 1120 Location: California or Guatemala or somewhere
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Posted: Wed Apr 27, 2011 3:11 am Post subject: Q |
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RioRico wrote:
There are only two ways to increase the magnification of a lens: add another lens to it, or extend its distance from the frame (film or sensor). Add-on close-up lenses and magnifying teleconverters do the first, but with some loss of image quality (IQ). Extension does the second, with no loss of IQ, but with a loss of light.
A 'macro' camera lens is built so that it can be extended on its own body. So, my Vivitar 90/2.8 macro or Macro-Takumar 50/4 can extend out to double the normal length of a 90mm or 50mm lens, and thus can attain 1:1 magnification. Other macro camera lenses may not extend as far, and may only reach 1:2.
With tubes or bellows, you push the lens objective further from the frame. One very popular combination is the Industar-50/3.5 lens, which may cost about US$25, put onto a set of M42 macro tubes, which may cost US$7. The 50mm lens body, placed on 50mm of tube extension, can now reach 1:1.
Tubes are simple and cheap but the only way to change magnification and focal distance is to change tubes. A bellows is much more flexible, and may only cost US$25-40 on eBay. I like to use cheap sharp enlarger lenses on bellows. The lenses often cost US$10 or less, and if they are longer than 80mm, they will reach infinity focus and so can be used for non-macro general photography too.
My Vivitar-Komine 90/2.8 macro is a fine M42 lens, very sharp and easy to use. It is also rather heavy. More often, I use a light-weight combo of inexpensive 90mm or 100mm or 105mm or 110mm enlarger lens on small Bellowscope bellows; the combination weighs half as much, and costs considerably less than a camera macro lens. Both enlarger and macro lenses are built for edge-to-edge flatfield sharpness. A good enlarger lens on bellows is every bit as good, or better, than a camera macro lens. _________________ Too many film+digi cams+lenses, oh my -- Pentax K20D, K-1000, M42s, more
The simple truth is this: There are no neutral photographs. --F-Stop Fitzgerald |
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newton
Joined: 10 Mar 2011 Posts: 343 Location: USA
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Posted: Wed Apr 27, 2011 1:43 pm Post subject: |
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newton wrote:
Why did they ever invent magnifying teleconverters then since IQ is affected so much?
I remember in the 70's and 80's these were popular sales items by camera stores.
My Vivitar 100 mm 2.8 seems crappy to me, btw. |
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visualopsins
Joined: 05 Mar 2009 Posts: 10807 Location: California
Expire: 2025-04-11
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Posted: Wed Apr 27, 2011 5:43 pm Post subject: |
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visualopsins wrote:
TC doesn't affect lens focus distance, can focus infinity. Add tube to focus closer, but lose ability to focus infinity. _________________ ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮ like attracts like! ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮
Cameras: Sony ILCE-7RM2, Spotmatics II, F, and ESII, Nikon P4
Lenses:
M42 Asahi Optical Co., Takumar 1:4 f=35mm, 1:2 f=58mm (Sonnar), 1:2.4 f=58mm (Heliar), 1:2.2 f=55mm (Gaussian), 1:2.8 f=105mm (Model I), 1:2.8/105 (Model II), 1:5.6/200, Tele-Takumar 1:5.6/200, 1:6.3/300, Macro-Takumar 1:4/50, Auto-Takumar 1:2.3 f=35, 1:1.8 f=55mm, 1:2.2 f=55mm, Super-TAKUMAR 1:3.5/28 (fat), 1:2/35 (Fat), 1:1.4/50 (8-element), Super-Multi-Coated Fisheye-TAKUMAR 1:4/17, Super-Multi-Coated TAKUMAR 1:4.5/20, 1:3.5/24, 1:3.5/28, 1:2/35, 1:3.5/35, 1:1.8/85, 1:1.9/85 1:2.8/105, 1:3.5/135, 1:2.5/135 (II), 1:4/150, 1:4/200, 1:4/300, 1:4.5/500, Super-Multi-Coated Macro-TAKUMAR 1:4/50, 1:4/100, Super-Multi-Coated Bellows-TAKUMAR 1:4/100, SMC TAKUMAR 1:1.4/50, 1:1.8/55
M42 Carl Zeiss Jena Flektogon 2.4/35
Contax Carl Zeiss Vario-Sonnar T* 28-70mm F3.5-4.5
Pentax K-mount SMC PENTAX-A ZOOM 1:3.5 35~105mm, SMC PENTAX ZOOM 1:4 45~125mm
Nikon Micro-NIKKOR-P-C Auto 1:3.5 f=55mm, NIKKOR-P Auto 105mm f/2.5 Pre-AI (Sonnar), Micro-NIKKOR 105mm 1:4 AI, NIKKOR AI-S 35-135mm f/3,5-4,5
Tamron SP 17mm f/3.5 (51B), Tamron SP 17mm f/3.5 (151B), SP 500mm f/8 (55BB), SP 70-210mm f/3.5 (19AH)
Vivitar 100mm 1:2.8 MC 1:1 Macro Telephoto (Kiron)
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gearsNcogs
Joined: 20 Oct 2010 Posts: 215
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Posted: Thu Apr 28, 2011 3:21 am Post subject: |
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gearsNcogs wrote:
Thanks for that fantastic info RioRico! _________________ Stills: SLR: Asahi Pentax Spotmatic SP, DSLR: Canon EOS Rebel XTi, Canon EOS 7D
Cine: 16mm: Krasnogorsk-3 (M42 mount) 8mm: Revere Model 88 Super 8: Bell and Howell 1235 XL Filmosonic
MF Lenses: M42: Meteor 5-1 KMZ 17-69mm 1:1,9 (Cine Only), Asahi Super Takumar 50mm 1:1.4, Focal MC 28mm 1:2.8, Tele-Lentar 135mm 1:2.8, Helios-44 KMZ 58mm 1:2, Helios-44-2 KMZ 58mm 1:2 M39: Industar-26M 50mm 1:2.8 F: Nikon Nikkor 50mm 1:1.8 EF: Lensbaby Composer f2 w/Double Glass Optic, Rokinon 35mm 1:1.4 AS UMC, Rokinon 85mm T1.5 AS IF UMC
AF Lenses: EF-S: Canon EF-S 18-55mm 1:3.5-5.6 II, EF: Tamron AF 70-300mm 1:4-5.6 TELE-MACRO (1:2), Canon EF 50mm 1:1.8 II
Fixed-Focus Lenses: D: Elitar 6.5mm 1:1.9, Wollensak-Revere 13mm 1:2.5 Velostigmat |
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adityap
Joined: 11 Aug 2010 Posts: 51 Location: Pune, India
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Posted: Thu Apr 28, 2011 4:49 am Post subject: |
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adityap wrote:
Very informative post Rico, thanks a lot |
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Arkku
Joined: 28 Feb 2007 Posts: 1416 Location: Helsinki, Finland
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Posted: Thu Apr 28, 2011 6:41 am Post subject: |
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Arkku wrote:
Actually the third way to “add macro” is to reverse the lens. =)
The reason why this works is that the point of focus is then where the film/sensor would normally be, which is much closer than the minimum focus distance of a typical lens. Since the lens is the same but focused closer, magnification will increase…
The underlying reason why extension tubes work is also that they simply allow you to focus closer. With “zero extension” the lens is focused at infinity, and the more extension you add (by moving the lens farther from the film/sensor) the closer it focuses. With extension equal to focal length (e.g. 50mm tubes with 50mm lens at infinity setting) magnification will equal 1:1. Not much higher magnification can usually be reached with tubes (alone) because the focus distance will soon become impractical.
You can combine reversing and tubes, though, or you can reverse a shorter lens in front of a longer one to get magnification approx. equal to the ratio of the focal lengths (e.g. 200mm on camera with 50mm reversed in front of it gives 200mm : 50mm = 4:1 magnification). |
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RioRico
Joined: 12 Mar 2010 Posts: 1120 Location: California or Guatemala or somewhere
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Posted: Thu Apr 28, 2011 8:34 am Post subject: |
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RioRico wrote:
Well, actually, reversing a camera lens brings the focus much closer, but does not magnify. Magnification comes from extension. Camera lenses may have front insets of various depths. Reversing a deep-inset camera lens DOES provide some extension and thus magnification. Reversing a shallow-inset camera lens, does not. (And newcomers complain about this!) For increased magnification with a reversed camera lens, I add short macro tubes or even just some step-rings.
Camera lenses are built so that one side (the object field) can focus out to infinity, while the other side (the image field) sharply projects an image a short distance to the frame (film or sensor). The distance from the lens mount to the frame is called the register or flange focal distance, and it's essentially the working distance of a reversed prime camera lens. Register can be very short, like 20mm for m4/3 systems or around 28mm for old Leica lenses, to fairly long, like around 46mm for Pentax or Nikon, and even longer for medium-format camera lenses.
Yes, primes can be reverse-stacked, where a shorter lens is reversed on a longer lens. This is the same sort of lens supplement as if you had added a close-up adapter, but the reversed lens is better-corrected for optical aberrations than are most such adapters.
________________________________________
I found a neat trick: Cheap zoom lenses improve when reversed! Exact results will vary with the lens, but here is my story. I reversed an SMC-A 35-80/4-5.6 zoom, arguably one of the crappiest lenses ever sold by Pentax, onto my K20D. I used only a simple 49mm-PK mount-reversal ring (US$5). I found that at 35mm, I could reach 2:1 magnification at a working distance of about 50mm / 2in; at 80mm, I could focus as close as 150mm / 6in, and out beyond infinity. And the images are sharp!
I also tried that with a 'better' zoom, a Tamron 28-70. To mount it, I used a 55mm-PK mount-reversal ring and a 52-55mm step ring. That combo, and the slightly deeper front inset of the Tamron, provided enough extra extension that 35mm magnification increased to abound 2.5:1, but the long end could not focus to infinity. And I tried a Tokina RMC 35-135/3.5-4.5 with the 55mm-PK ring. but found that the old one-touch push-pull zoom design was a bit too loose for careful macro work. So, when reversing a zoom, Your Mileage May Vary.
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One last note: No non-reversed lens can focus closer than its focal length. No matter how much extension is put on a 50mm lens, it can never focus closer than 50mm. Great extension may result in great magnification, but you can't get any closer! The result: Shorter lenses are great for working very close, for easily filling the frame. Longer lenses allow (or force!) you to work from further way. 35-55mm may be ideal for studio work. 90-200mm may be needed for field work, lest the bugs be frightened away by a lens poking too close to them. _________________ Too many film+digi cams+lenses, oh my -- Pentax K20D, K-1000, M42s, more
The simple truth is this: There are no neutral photographs. --F-Stop Fitzgerald |
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Arkku
Joined: 28 Feb 2007 Posts: 1416 Location: Helsinki, Finland
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Posted: Thu Apr 28, 2011 10:39 am Post subject: |
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Arkku wrote:
RioRico wrote: |
Well, actually, reversing a camera lens brings the focus much closer, but does not magnify. Magnification comes from extension. |
Magnification comes from focus distance relative to focal length.
(Of course one needs to realize that the distance is not measured from the physical end of the lens body, so the “optical” distance may be different than it would appear.) |
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