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dalla
Joined: 29 Mar 2011
Posts: 5
Location: Sweden
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 Posted: Thu Mar 31, 2011 7:12 pm Post subject: DoF 50mm lens difference? |
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dalla wrote:
I tried two 50mm lenses today and notices that the DoF was difference between the lenses at same aperture.
The two lenses was a Rokkor 50mm 1.4 and a Yashica 50mm 1.7. How could the depth of field not be the same when the same aperture is set?
Have I missed something in the theory of photography or could it be because of the difference in adapters used on my m4/3 camera? |
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aleksanderpolo
Joined: 24 Jan 2010
Posts: 684
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| Posted: Thu Mar 31, 2011 7:23 pm Post subject: |
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aleksanderpolo wrote:
I had the same question before, but apparently the DOF formula is only for a theoretical lens, for actual lens with different formula, they can have different DOF at the same focal length and F number. I don't completely understand this, but people often comment:
C/Y distagon 35/1.4 has narrower DOF than other 35/1.4 lens.
C/Y distagon 21/2.8 has seemingly deeper DOF than other lens. |
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LucisPictor
Joined: 26 Feb 2007
Posts: 17633
Location: Oberhessen, Germany / Maidstone ('95-'96)
Expire: 2013-12-03
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| Posted: Thu Mar 31, 2011 8:10 pm Post subject: |
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LucisPictor wrote:
1) The f-stops are never really 100% precise. With one lens f/1.7 mean perhaps f/1.61 and with another lens f/1.79.
2) We can never be sure that the focus is absolutely identical, and especially for close-ups even the slightest focus difference can have an effect in DoF.
3) The focal length of different 50mm lenses are not exactly 50mm, some are 47mm, others are 53mm or so...
When these three aspects come together the difference can be considerable.
Lens A: 53mm with f/1.61
Lens B: 48mm with f/1.79
Plus a slightly different focus setting
and you will generate a different DoF.
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dalla
Joined: 29 Mar 2011
Posts: 5
Location: Sweden
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| Posted: Thu Mar 31, 2011 8:50 pm Post subject: |
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dalla wrote:
This makes sense. Thanks! |
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visualopsins
Joined: 05 Mar 2009
Posts: 10543
Location: California
Expire: 2025-04-11
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| Posted: Thu Mar 31, 2011 11:38 pm Post subject: |
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visualopsins wrote:
Welcome dalla!
There is another message thread here about this: http://forum.mflenses.com/viewtopic.php?t=37692
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☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮ 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 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 (51BB), 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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newton
Joined: 10 Mar 2011
Posts: 343
Location: USA
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| Posted: Sat Apr 02, 2011 6:27 am Post subject: |
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newton wrote:
| LucisPictor wrote: |
1) The f-stops are never really 100% precise. With one lens f/1.7 mean perhaps f/1.61 and with another lens f/1.79.
2) We can never be sure that the focus is absolutely identical, and especially for close-ups even the slightest focus difference can have an effect in DoF.
3) The focal length of different 50mm lenses are not exactly 50mm, some are 47mm, others are 53mm or so...
When these three aspects come together the difference can be considerable.
Lens A: 53mm with f/1.61
Lens B: 48mm with f/1.79
Plus a slightly different focus setting
How can you measure this precisely? Thx.
and you will generate a different DoF. |
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AhamB
Joined: 22 Jun 2008
Posts: 733
Location: Germany
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| Posted: Sat Apr 02, 2011 9:58 am Post subject: |
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AhamB wrote:
I think that what aleksanderpolo is saying may actually play a bigger role than deviations in the FL and aperture size.
@visualopsins: Thanks for that link! Very interesting page on POTN. I had seen other comparisons from denoir between the Rollei Distagon 35/1.4 and the Leica Summilux-M 35/1.4, where the Rollei has significantly shallower DOF. |
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aleksanderpolo
Joined: 24 Jan 2010
Posts: 684
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| Posted: Sat Apr 02, 2011 5:45 pm Post subject: |
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aleksanderpolo wrote:
| AhamB wrote: |
I think that what aleksanderpolo is saying may actually play a bigger role than deviations in the FL and aperture size.
@visualopsins: Thanks for that link! Very interesting page on POTN. I had seen other comparisons from denoir between the Rollei Distagon 35/1.4 and the Leica Summilux-M 35/1.4, where the Rollei has significantly shallower DOF. |
I was unconvinced that two lens of the same focal length at the same F stop can have different DOF, until I saw Denoir's comparison between the Distagon 35/1.4 and Lux 35/1.4.
I think some have commented that images made with Distagon 35/1.4 have a feel of MF to it, perhaps its due to its shallower DOF |
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visualopsins
Joined: 05 Mar 2009
Posts: 10543
Location: California
Expire: 2025-04-11
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| Posted: Sat Apr 02, 2011 6:19 pm Post subject: |
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visualopsins wrote:
If I understand correctly, the DOF calculator works fine for lens well corrected for CA, but overestimates DOF for lenses with CA. The DOF for lenses with CA also depends on colors in scene. For lenses partially corrected for CA, scene color effects depend on how correction is applied in lens formula -- some formulas shift the red, some blue, others both, to correct CA.
_________________
☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮ 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 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 (51BB), 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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