| View previous topic :: View next topic |
| Author |
Message |
guardian
Joined: 18 Mar 2009
Posts: 1747
|
 Posted: Sun Mar 24, 2013 2:15 pm Post subject: Front/rear element flipping |
 |
|
guardian wrote:
This is limited to lenses having front and/or rear elements which are "flippable". "Flippable" in this instance means symmetrical. A lens convex on one side and concave on the other obviously is not flippable. A lens having dissimilar curvatures front and rear is not "flippable".
That said:
What are the merits of renewing the exposed surface of a front or rear element by flipping? Depending on the lens's age and the amount of wear and tear to which it has been subjected over many years, might this not be something to consider?
For scratched lenses, would it not be better if light incident upon the lens encounters a first surface free of scratches, even if that means the exit surface will have the scratches, instead? To the extent scratches or imperfection trap dirt, would it not be better to face the scratches toward the lens's interior, where the environment is surely cleaner?
Lens flipping, when possible, seems to me something to consider. What do you think? |
|
| Back to top |
|
 |
RSalles
Joined: 12 Aug 2012
Posts: 1376
Location: Brazil - RS / South
|
| Posted: Sun Mar 24, 2013 4:53 pm Post subject: |
|
|
RSalles wrote:
I think that is better to know which can be flipped and to avoid a lens like this from a not proven reputation's seller,
[]s,
Renato |
|
| Back to top |
|
|
Orio
Joined: 24 Feb 2007
Posts: 29658
Location: West Emilia
Expire: 2012-12-04
|
| Posted: Sun Mar 24, 2013 5:04 pm Post subject: |
|
|
Orio wrote:
What may look like flippable, may actually be not.
_________________
Orio, Administrator
T*
NE CEDE MALIS AUDENTIOR ITO
Ferrania film is reborn! http://www.filmferrania.it/
Support the Ornano film chemicals company and help them survive!
http://forum.mflenses.com/ornano-chemical-products-t55525.html |
|
| Back to top |
|
|
martinsmith99
Joined: 31 Aug 2008
Posts: 6968
Location: S Glos, UK
Expire: 2013-11-18
|
| Posted: Sun Mar 24, 2013 6:42 pm Post subject: |
|
|
martinsmith99 wrote:
if the lens is scratched, it's scratched, no matter which side points outwards.
_________________
No longer here |
|
| Back to top |
|
|
guardian
Joined: 18 Mar 2009
Posts: 1747
|
| Posted: Sun Mar 24, 2013 8:25 pm Post subject: |
|
|
guardian wrote:
| martinsmith99 wrote: |
| if the lens is scratched, it's scratched, no matter which side points outwards. |
Agreed
Lenses bend light, though. Light incident upon the lens's first surface, however, is not yet bent, whereas light exiting the lens already has been bent by the lens's optical properties.
Also, regarding coatings:
If the old surface has imperfections in its coating, owing for example to over-exuberant cleaning, while the flipped lens offers (to incident light) a fresh, new, and perfect coating, would that not be an advantage? Coatings matter too, of course, inside the lens. But would not the coating quality of the first surface matter more? |
|
| Back to top |
|
|
visualopsins
Joined: 05 Mar 2009
Posts: 10362
Location: California
Expire: 2021-06-22
|
| Posted: Sun Mar 24, 2013 10:55 pm Post subject: |
|
|
visualopsins wrote:
I don't think there are any camera lenses with any element having identical curvatures both sides.
If there are any, surely factory couldn't say which side is which, eh? 
Rear element scratches show in images, while front element scratches rarely show other than loss of contrast. Scratches show when angle of incidence is steep enough...
_________________
☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮ like attracts like! ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮
Cameras: Sony A7Rii, Spotmatics II, F, and ESII, Nikon P4
M42 Asahi Optical Co., Lenses:
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
Other lenses:
Carl Zeiss Jena Flektogon 2.4/35
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
|
|
| Back to top |
|
|
guardian
Joined: 18 Mar 2009
Posts: 1747
|
| Posted: Mon Mar 25, 2013 12:00 pm Post subject: |
|
|
guardian wrote:
| visualopsins wrote: |
I don't think there are any camera lenses with any element having identical curvatures both sides.
If there are any, surely factory couldn't say which side is which, eh?
Rear element scratches show in images, while front element scratches rarely show other than loss of contrast. Scratches show when angle of incidence is steep enough... |
I appreciate your comments. First of all, I should have paid better attention in high school physics!
But just on gut instinct, and thinking about this only following the insight provided by your post, I tend to agree with you about lack of front element symmetry. This is something to which I shall be paying much more attention going forward!!  |
|
| Back to top |
|
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Search
Memberlist
Register
Profile
Log in to check your private messages
Log in
