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tb_a
Joined: 26 Jan 2010 Posts: 3678 Location: Austria
Expire: 2019-08-28
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Posted: Wed Mar 21, 2018 4:51 pm Post subject: Lens Turbo AKA Speed Booster |
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tb_a wrote:
I've done a comparison of the combination of a 50mm lens at F4 in combination with Zhongyi's Lens Turbo and a glass-less adapted 35mm lens at F2.8. Both pictures have been shot with tripod from exactly the same distance. Exposure times have been the same; i.e. the focal reduced F4 lens actually needs the same exposure time like the F2.8 lens. Camera was the NEX-C3 16MP APS-C.
Minolta MD 50mm/F1.4 at F4 on Lens Turbo:
Minolta MD 35mm/F2.8 at F2.8:
In the second comparison I compared a 50mm lens + LT on the NEX with the same lens on the FF Sony A850 (both fully open):
Voigtlaender Color-Ultron 50mm/F1.8 + LT on NEX-C3:
Voigtlaender Color-Ultron 50mm/F1.8 on A850:
The same comparison with the Color-Ultron outdoor at infinity landscape (LT/NEX against A850) was likewise clearly in favor of the FF picture as the picture corners from the LT have been really lousy; i.e. totally unsharp. At closer distance this isn't that obvious.
However, even the old Lens Turbo seems to have some advantages, particularly if there is neither a FF camera nor a real wide angle lens on hand.
BTW, I made this comparisons because of heavy discussions in an other forum. There the theory came in that a so called "focal reducer" is able to change a 50mm lens into a BETTER and REAL 35mm lens. Besides that I doubt that a focal reducer is able to make from a mediocre lens a better one, I really oppose the definition that it will change any existing lens into a new one with shorter focal length. I would likewise not call a 50mm lens with a 2X converter a 100mm lens or any lens a "macro lens" just because it was used with extension rings.
Would be nice if some of the folks here let me know their point of view about the definition of a focal reduced lens; i.e. will it change it's focal length to be a new 35mm lens (to stay with this example) or will it still be simply a focally reduced 50mm lens (my preferred definition)?
Cheers, _________________ Thomas Bernardy
Manual focus lenses mainly from Minolta, Pentax, Voigtlaender, Leitz, Topcon and from Russia (too many to be listed here). |
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Sjak
Joined: 29 Sep 2017 Posts: 696
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Posted: Wed Mar 21, 2018 5:25 pm Post subject: |
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Sjak wrote:
Technically, the focal length is the lens' FL multiplied by the adaper's factor (often 0.71 for reducers, 1.4 or 2* for tele converters)
As for preferred vocabulary for describing such a combination, I have no real opinion. We have freedom of speech
It could be helpful to refer to "lens x mm with y* converter" when describing the combination. |
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kds315*
Joined: 12 Mar 2008 Posts: 16544 Location: Weinheim, Germany
Expire: 2021-03-09
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Posted: Thu Mar 22, 2018 1:48 am Post subject: |
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kds315* wrote:
Gosh how I hate to say that AGAIN: the lens focal length IS NOT CHANGED when using a speed booster / focal reducer, only the angle of view AS SEEN BY THE SENSOR is, as the FF coverage is reduced to a (say) 0.7x sensor size (actually the projected image diameter is. It just APPEARS as if the focal length has changed ... _________________ Klaus - Admin
"S'il vient a point, me souviendra" [Thomas Bohier (1460-1523)]
http://www.macrolenses.de for macro and special lens info
http://www.pbase.com/kds315/uv_photos for UV Images and lens/filter info
https://www.flickr.com/photos/kds315/albums my albums using various lenses
http://photographyoftheinvisibleworld.blogspot.com/ my UV BLOG
http://www.travelmeetsfood.com/blog Food + Travel BLOG
https://galeriafotografia.com Architecture + Drone photography
Currently most FAV lens(es):
X80QF f3.2/80mm
Hypergon f11/26mm
ELCAN UV f5.6/52mm
Zeiss UV-Planar f4/60mm
Zeiss UV-Planar f2/62mm
Lomo Уфар-12 f2.5/41mm
Lomo Зуфар-2 f4.0/350mm
Lomo ZIKAR-1A f1.2/100mm
Nikon UV Nikkor f4.5/105mm
Zeiss UV-Sonnar f4.3/105mm
CERCO UV-VIS-NIR f1.8/45mm
CERCO UV-VIS-NIR f4.1/94mm
CERCO UV-VIS-NIR f2.8/100mm
Steinheil Quarzobjektiv f1.8/50mm
Pentax Quartz Takumar f3.5/85mm
Carl Zeiss Jena UV-Objektiv f4/60mm
NYE OPTICAL Lyman-Alpha II f1.1/90mm
NYE OPTICAL Lyman-Alpha I f2.8/200mm
COASTAL OPTICS f4/60mm UV-VIS-IR Apo
COASTAL OPTICS f4.5/105mm UV-Micro-Apo
Pentax Ultra-Achromatic Takumar f4.5/85mm
Pentax Ultra-Achromatic Takumar f5.6/300mm
Rodenstock UV-Rodagon f5.6/60mm + 105mm + 150mm
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calvin83
Joined: 12 Apr 2009 Posts: 7554 Location: Hong Kong
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Posted: Thu Mar 22, 2018 2:22 am Post subject: |
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calvin83 wrote:
Yes. A focal reducer works exactly opposite as a tele-converter. They don't change the real focal length of the lens but reduce/magnify the image circle. _________________ https://lensfever.com/
https://www.instagram.com/_lens_fever/
The best lens is the one you have with you. |
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tb_a
Joined: 26 Jan 2010 Posts: 3678 Location: Austria
Expire: 2019-08-28
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Posted: Thu Mar 22, 2018 2:27 am Post subject: |
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tb_a wrote:
kds315* wrote: |
Gosh how I hate to say that AGAIN: the lens focal length IS NOT CHANGED when using a speed booster / focal reducer, only the angle of view AS SEEN BY THE SENSOR is, as the FF coverage is reduced to a (say) 0.7x sensor size (actually the projected image diameter is. It just APPEARS as if the focal length has changed ... |
I really tried hard to convince the people at DPR's "Adapted Lens Talk" but I simply had no chance alone in the desert.
At least here I'm not alone.... _________________ Thomas Bernardy
Manual focus lenses mainly from Minolta, Pentax, Voigtlaender, Leitz, Topcon and from Russia (too many to be listed here). |
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luisalegria
Joined: 07 Mar 2008 Posts: 6627 Location: San Francisco, USA
Expire: 2018-01-18
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Posted: Thu Mar 22, 2018 5:30 am Post subject: |
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luisalegria wrote:
The image circle effect is exactly the point.
I'm quite impressed by my cheapo focal reducer actually.
Very handy, makes a 50mm more useful for max bokeh - with a bigger image you get more of it!
And its great for available light. The cheap 50/1.4 becomes quite a lot more like a 35mm f/1.2 - hey, I have to buy that 7Artisans thing!
That is, if all you've got is an APS-C camera. And you are ok with bulky lenses. And you dont care about corners.
Talking about bulky lenses, when I get time I need to try my 180 Sonnar on that thing. _________________ I like Pentax DSLR's, Exaktas, M42 bodies of all kinds, strange and cheap Japanese lenses, and am dabbling in medium format/Speed Graphic work. |
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ZoneV
Joined: 09 Nov 2009 Posts: 1633 Location: Germany
Expire: 2011-12-02
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Posted: Thu Mar 22, 2018 7:43 am Post subject: |
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ZoneV wrote:
kds315* wrote: |
Gosh how I hate to say that AGAIN: the lens focal length IS NOT CHANGED when using a speed booster / focal reducer, only the angle of view AS SEEN BY THE SENSOR is, as the FF coverage is reduced to a (say) 0.7x sensor size (actually the projected image diameter is. It just APPEARS as if the focal length has changed ... |
The lens system (front-lens + booster) focal length is changed, and the speed too. _________________ Camera modification, repair and DIY - some links to look through: http://www.4photos.de/camera-diy/index-en.html
I AM A LENS NERD!
Epis, Elmaron, Emerald, Ernostar, Helioplan and Heidosmat.
Epiotar, Kameraobjektiv, Anastigmat, Epis, Meganast, Magnagon, Quinar, Culmigon, Novotrinast, Novflexar, Colorplan, Sekor, Kinon, Talon, Telemegor, Xenon, Xenar, Ultra, Ultra Star. Tessar, Janar, Visionar, Kiptar, Kipronar and Rotelar.
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tb_a
Joined: 26 Jan 2010 Posts: 3678 Location: Austria
Expire: 2019-08-28
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Posted: Thu Mar 22, 2018 9:41 am Post subject: |
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tb_a wrote:
luisalegria wrote: |
The image circle effect is exactly the point.
I'm quite impressed by my cheapo focal reducer actually.
Very handy, makes a 50mm more useful for max bokeh - with a bigger image you get more of it!
And its great for available light. The cheap 50/1.4 becomes quite a lot more like a 35mm f/1.2 - hey, I have to buy that 7Artisans thing!
That is, if all you've got is an APS-C camera. And you are ok with bulky lenses. And you dont care about corners.
Talking about bulky lenses, when I get time I need to try my 180 Sonnar on that thing. |
Good idea. It never came into my mind to use any tele lens in a speed booster combination. However, the shorter exposure times may make sense to use it. Particularly with the excellent MD 200mm/F4 lens which is "boosted to F2.8" equivalence.
I'm really impressed by the result although it's only the first version of the cheap Chinese Zhongyi "Lens Turbo".
Here we go (all shot at maximum aperture):
Minolta MD 200mm/F4 direct:
Minolta MD 200mm/F4 on LT:
Minolta MD 300mm/F4.5 IF direct:
Minolta MD 300mm/F4.5 IF on LT:
_________________ Thomas Bernardy
Manual focus lenses mainly from Minolta, Pentax, Voigtlaender, Leitz, Topcon and from Russia (too many to be listed here). |
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tb_a
Joined: 26 Jan 2010 Posts: 3678 Location: Austria
Expire: 2019-08-28
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Posted: Thu Mar 22, 2018 10:45 am Post subject: |
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tb_a wrote:
Finally two other rather extreme examples; again same distance and fully open.
Minolta RF 500mm/F8 direct:
Minolta RF 500mm/F8 on LT:
Minolta MC 58mm/F1.2 direct:
Minolta MC 58mm/F1.2 on LT:
After all, I now have a lens faster than F1.0.
Seriously, I think that when people claim that any speed booster is able to make any lens better that this is only an impression. Logically, when used on tele lenses, the smaller magnification in combination with a speed booster looks a little bit sharper. If watched at same size at 100% crop, i.e. in pixel peeping mode, this isn't any longer the case.
BTW, I think it's time to clean the RF500. _________________ Thomas Bernardy
Manual focus lenses mainly from Minolta, Pentax, Voigtlaender, Leitz, Topcon and from Russia (too many to be listed here). |
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kds315*
Joined: 12 Mar 2008 Posts: 16544 Location: Weinheim, Germany
Expire: 2021-03-09
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Posted: Thu Mar 22, 2018 1:06 pm Post subject: |
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kds315* wrote:
ZoneV wrote: |
kds315* wrote: |
Gosh how I hate to say that AGAIN: the lens focal length IS NOT CHANGED when using a speed booster / focal reducer, only the angle of view AS SEEN BY THE SENSOR is, as the FF coverage is reduced to a (say) 0.7x sensor size (actually the projected image diameter is. It just APPEARS as if the focal length has changed ... |
The lens system (front-lens + booster) focal length is changed, and the speed too. |
Yes, correct for the SYSTEM, but not for the LENS _________________ Klaus - Admin
"S'il vient a point, me souviendra" [Thomas Bohier (1460-1523)]
http://www.macrolenses.de for macro and special lens info
http://www.pbase.com/kds315/uv_photos for UV Images and lens/filter info
https://www.flickr.com/photos/kds315/albums my albums using various lenses
http://photographyoftheinvisibleworld.blogspot.com/ my UV BLOG
http://www.travelmeetsfood.com/blog Food + Travel BLOG
https://galeriafotografia.com Architecture + Drone photography
Currently most FAV lens(es):
X80QF f3.2/80mm
Hypergon f11/26mm
ELCAN UV f5.6/52mm
Zeiss UV-Planar f4/60mm
Zeiss UV-Planar f2/62mm
Lomo Уфар-12 f2.5/41mm
Lomo Зуфар-2 f4.0/350mm
Lomo ZIKAR-1A f1.2/100mm
Nikon UV Nikkor f4.5/105mm
Zeiss UV-Sonnar f4.3/105mm
CERCO UV-VIS-NIR f1.8/45mm
CERCO UV-VIS-NIR f4.1/94mm
CERCO UV-VIS-NIR f2.8/100mm
Steinheil Quarzobjektiv f1.8/50mm
Pentax Quartz Takumar f3.5/85mm
Carl Zeiss Jena UV-Objektiv f4/60mm
NYE OPTICAL Lyman-Alpha II f1.1/90mm
NYE OPTICAL Lyman-Alpha I f2.8/200mm
COASTAL OPTICS f4/60mm UV-VIS-IR Apo
COASTAL OPTICS f4.5/105mm UV-Micro-Apo
Pentax Ultra-Achromatic Takumar f4.5/85mm
Pentax Ultra-Achromatic Takumar f5.6/300mm
Rodenstock UV-Rodagon f5.6/60mm + 105mm + 150mm
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luisalegria
Joined: 07 Mar 2008 Posts: 6627 Location: San Francisco, USA
Expire: 2018-01-18
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Posted: Thu Mar 22, 2018 2:57 pm Post subject: |
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luisalegria wrote:
Good point!
Make some tele lenses more hand-holdable by increasing shutter speeds.
I was thinking of the larger defocused field of view, as you show with the 58mm. More bokeh, and for that purpose who cares about corners. _________________ I like Pentax DSLR's, Exaktas, M42 bodies of all kinds, strange and cheap Japanese lenses, and am dabbling in medium format/Speed Graphic work. |
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DConvert
Joined: 12 Jun 2010 Posts: 902 Location: Essex UK
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Posted: Thu Mar 22, 2018 5:16 pm Post subject: |
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DConvert wrote:
kds315* wrote: |
ZoneV wrote: |
kds315* wrote: |
Gosh how I hate to say that AGAIN: the lens focal length IS NOT CHANGED when using a speed booster / focal reducer, only the angle of view AS SEEN BY THE SENSOR is, as the FF coverage is reduced to a (say) 0.7x sensor size (actually the projected image diameter is. It just APPEARS as if the focal length has changed ... |
The lens system (front-lens + booster) focal length is changed, and the speed too. |
Yes, correct for the SYSTEM, but not for the LENS |
The Lens & booster combined system is as far as the camera is concerned a lens, and most photographers would use it in this way.
Being pedantic & splitting the two is a little like claiming the focal length of the lens is actually that of it's first element (which is itself a lens).
This is nothing like the situation with a cropped sensor, where the focal length remains the same. |
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woodrim
Joined: 14 Jan 2010 Posts: 4060 Location: Charleston
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Posted: Thu Mar 22, 2018 10:53 pm Post subject: |
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woodrim wrote:
Focal length of a lens does not change but the field of view does. The same has always been true whether using on a larger format where field of view becomes wider or a crop camera where it becomes more narrow. The whole crop factor thing strikes me as an arbitrary decision made to help people relate to what most were used to with 35mm film cameras.
I've used a 1.5 crop for so long I suppose today with FF it becomes a .66 crop _________________ Regards,
Woodrim |
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cooltouch
Joined: 15 Jan 2009 Posts: 9097 Location: Houston, Texas
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Posted: Fri Mar 23, 2018 3:05 pm Post subject: |
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cooltouch wrote:
I have a question about focal reducers: will a focal reducer, when converting a given lens to an obvious wide angle field of view, does it increase the apparent depth of field in the same way a "native" wide angle lens would? Let's say that the lens with reducer is set so that its increased aperture ratio is set to duplicate the same aperture as is used with the 'native' wide angle? So you would, what? Stop down the lens with reducer one stop more? And at that point, is there a difference in depth of field? _________________ Michael
My Gear List: http://michaelmcbroom.com/photo/gear.html
My Gallery: http://michaelmcbroom.com/gallery3/index.php/
My Flickr Page: https://www.flickr.com/photos/11308754@N08/albums
My Music: https://soundcloud.com/michaelmcbroom/albums
My Blog: http://michaelmcbroom.com/blogistan/ |
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luisalegria
Joined: 07 Mar 2008 Posts: 6627 Location: San Francisco, USA
Expire: 2018-01-18
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Posted: Fri Mar 23, 2018 4:12 pm Post subject: |
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luisalegria wrote:
Cooltouch,
The difference in depth of field comes in when you use the same framing for a subject. With a focal reducer, for the same frame, you can come much closer (limited by how close the lens focuses of course), reducing the effective DOF and getting more bokeh.
Same as if comparing full frame sensor vs crop sensors, or for that matter Large format vs medium format vs 35mm.
DOF is affected by focal length, aperture and distance. _________________ I like Pentax DSLR's, Exaktas, M42 bodies of all kinds, strange and cheap Japanese lenses, and am dabbling in medium format/Speed Graphic work. |
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tb_a
Joined: 26 Jan 2010 Posts: 3678 Location: Austria
Expire: 2019-08-28
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Posted: Fri Mar 23, 2018 6:26 pm Post subject: |
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tb_a wrote:
Michael, if you compare the first two pictures of this thread; i.e. the 50/1.4 stopped down to F4 against the 35/2.8 one fully open (exactly the same exposure time and same distance), you'll barely see any difference. Therefore I tend to say that the focal reduced lens is performing as if it would be the wide angle one in every respect incl. depth of field. _________________ Thomas Bernardy
Manual focus lenses mainly from Minolta, Pentax, Voigtlaender, Leitz, Topcon and from Russia (too many to be listed here). |
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cooltouch
Joined: 15 Jan 2009 Posts: 9097 Location: Houston, Texas
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