Site Sponsors
Results 1 to 24 of 24

Thread: In-Depth Articles on Lenses

  1. #1
    Not Available
    Join Date
    Jul 2009
    Location
    New York
    Posts
    1,864
    Post Thanks / Like

    In-Depth Articles on Lenses

    Hey, gang.

    I wrote an article over the weekend, the first in a series - about lenses. Not that we haven't heard it all before, but it has a decidedly M system slant to it. Since it's a "basics" kind of article, it's just that - defining a lens and its basic controls, etc.

    Today my mind was racing with ideas and I ended up just dumping it all into another article, which is the second of the series. It goes into more details about actually using a lens for creative purposes.

    There will be at least a third part, which I'm still formulating - which will cover more advanced topics. Things like chromatic and spherical aberrations, floating and aspherical elements, etc.

    Anyway, I thought I might mention them to my esteemed colleagues here at GetDPI for informational purposes and maybe to elicit a little peer review and see what y'all think. Feedback is always appreciated, of course. But I might point out that articles (and reviews) on the site are constantly updated to be as accurate and complete as possible rather than just gather dust. That and the fact that I get ideas after publishing and just don't have the time to do it all at once...

    Lens Primer - The Basics

    Lens Primer - Creative Controls

    Enjoy.

  2. #2
    Senior Member doug's Avatar
    Join Date
    Nov 2007
    Posts
    708
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    In the discussion of the M8's crop factor IMHO it's more accurate to apply the crop factor to the lens' field of view rather than to its focal length. The focal length doesn't change, the field of view does.

  3. #3
    Senior Member
    Join Date
    Jan 2010
    Posts
    519
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    What people care - is simply what they get. That is what they are interested in, when they attach FF lens to cropped body.

    In u43 world rule is very simple and straightforward:
    - multiply focal by 2, that will give you frame, borders, effective focal as on FF
    - multiply aperture by 2, that will give you DOF as on FF
    - multiply aperture by 1, that will give you exposure used aperture

    As an example - attaching 50mm f/1.4 lens to u43 body, will give you:
    - 100mm - effective focal as on FF
    - f/2.8 - DOF of such aperture at above focal as on FF
    - f/1.4 - aperture taken in exposure

    Of course the lens still stays 50mm and DOF is as DOF of 50mm lens on FF.
    Best Regards!

  4. #4
    Senior Member
    Join Date
    Jan 2010
    Posts
    519
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    PS:
    One more comment. Reading the article, I have feeling, that you mention perspective when writing about focal lengths, instead of camera subject distance.

    Perspective doesn't depend on focal length, but on distance between camera and subject.
    I assume you used common mental abbreviation, maybe it would be worth of clear distinction.

    See discussion here:
    http://www.l-camera-forum.com/leica-...ml#post1775367
    Best Regards!

  5. #5
    Senior Member
    Join Date
    Jul 2011
    Location
    Texas
    Posts
    408
    Post Thanks / Like
    Images
    1

    Re: In-Depth Articles on Lenses

    I think your article was great. Really informative for me..I'm new to rangefinders so everything you wrote was very helpful
    Great website

  6. #6
    Senior Member doug's Avatar
    Join Date
    Nov 2007
    Posts
    708
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    The problem with the 'effective focal length' terminology is that it confuses anyone who is trying to calculate bellows extension or close-up factors.

  7. #7
    Not Available
    Join Date
    Jul 2009
    Location
    New York
    Posts
    1,864
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Hard at work on the third article; "Lens Primer - Advanced Topics" and should be published later today, or worse comes to worse over the weekend. Stay tuned...

    Quote Originally Posted by Moonshine View Post
    I think your article was great. Really informative for me..I'm new to rangefinders so everything you wrote was very helpful
    Great website
    Awesome! Thank you.

    Quote Originally Posted by doug View Post
    The problem with the 'effective focal length' terminology is that it confuses anyone who is trying to calculate bellows extension or close-up factors.
    True... I should explain that a little more. As far as bellows and extension tubes - how many M users really use either?

  8. #8
    Not Available
    Join Date
    Jul 2009
    Location
    New York
    Posts
    1,864
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Thar she blows!

    Lens Primer - Advanced Topics

    This one was a little harder to write. Primarily to keep it simple enough for n00bs to wrap their heads around, but also to keep it to a reasonable size. I'll be adding some illustrations and sample photos, possibly other sections. But my brain is fried for today.

  9. #9
    Senior Member leicashot's Avatar
    Join Date
    Oct 2010
    Location
    Melbourne, Australia
    Posts
    525
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Quote Originally Posted by Jerry_R View Post
    PS:
    One more comment. Reading the article, I have feeling, that you mention perspective when writing about focal lengths, instead of camera subject distance.

    Perspective doesn't depend on focal length, but on distance between camera and subject.
    I assume you used common mental abbreviation, maybe it would be worth of clear distinction.

    See discussion here:
    http://www.l-camera-forum.com/leica-...ml#post1775367
    Gotta disagree. Perspective is dependent on focal length as each focal length carries a particular perspective with it.....ok my last post on GetDPI, cheers

    K

  10. #10
    Senior Member
    Join Date
    Jun 2010
    Location
    EU
    Posts
    325
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Double Negative, these are very good and interesting articles! I for example found very informative the chapter about different Leica and Zeiss lens names since I was just recently after such information being confused with all the strange names.

    However, I'm a bit confused who these articles are aimed for. This may be just me, but I see two approaches a bit mixed here: 1) readers who are quite new to photography and 2) readers who are familiar with photography and cameras in general but new to the world of Leica and rangefinders.

    If you plan to still add stuff to the articles, I have two suggestions. First, the rangefinder focusing is a bit difficult to understand for us who haven't used such a camera. Some sort of an explanation might be good to have. Second, in lenses perhaps one could explain the difference and similarities between LTM and the M39 thread that some older Russian glass use. I for example am confused with these lenses.

    But all together, a great contribution!

  11. #11
    Not Available
    Join Date
    Jul 2009
    Location
    New York
    Posts
    1,864
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Hmm, some interesting points regarding perspective. Indeed, it's got a lot to do with camera-subject distance; I went the focal length route because it's easy to understand in the context of the article (so called mental abbreviation, heheh). But I'll have to revisit it and maybe make some changes to make the distinction a bit clearer.

    As for who the articles are for... That's an interesting observation, and a good question. Somewhere in between someone new to photography and rangefinders to someone with a bit of exposure to photography in general I guess. Sort of a translation between SLRs and RFs (as these articles all have a strong M theme to them). I didn't want to make them too technical and dry and appeal to a broad audience. But also be useful on a technical/reference level.

    I can certainly add an explanatory section or better yet an entire article on the rangefinder mechanism, camera and how its different from an SLR, etc. I mean, that is a pretty big part of the equation.

    I've cleaned up the "effective" focal length sentence to basically just read "...effectively have a focal length of 100mm..." Shortcut? Yeah, guess so.

    Thanks for the feedback everyone, I truly appreciate it. I wrote all three of these articles rather quickly in the course of a week and it's good to get some fresh eyes on them that understand what the hell I'm talking about.

    Definitely glad they've already helped people - that's the whole point!

  12. #12
    Senior Member
    Join Date
    Jul 2011
    Location
    Texas
    Posts
    408
    Post Thanks / Like
    Images
    1

    Re: In-Depth Articles on Lenses

    An article on rangefinder focussing would be great!! Please write one

  13. #13
    Senior Member
    Join Date
    Apr 2011
    Location
    Santa Cruz, California
    Posts
    586
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Quote Originally Posted by leicashot View Post
    Gotta disagree. Perspective is dependent on focal length as each focal length carries a particular perspective with it.....ok my last post on GetDPI, cheers

    K
    Sorry but that's wrong - perspective is not a function of focal length; it is only a function of the location of the camera in relation to the subject (not just distance to subject as has been posted).

    This is easy to prove - take a wide angle shot and a telephoto shot of the same subject from the exact same camera position then crop the wide angle photo to match the fov of the telephoto shot. They will look exactly the same (barring any lens distortion) - ie the perspective is identical.

    You can also use this same method to show that the often misquoted "flattening" effect of telephoto lenses has nothing to do with the lens - it too is a matter of perspective and you will see the same flattening with the wide angle shot once it is cropped to match the telephoto fov.

    Cheers,
    -- Joe

    http://mountainjoe.zenfolio.com/ - excuse the mess

  14. #14
    Member
    Join Date
    Oct 2009
    Posts
    82
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    I think the tone's spot on. Making the switch myself from SLR to Leica M it's helpful to have a clear translation resource as I 'learn' about the options of my new world. Thanks for [big] efforts!

    -Jeff

  15. #15
    Senior Member
    Join Date
    Jan 2010
    Posts
    519
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Best Regards!

  16. #16
    Senior Member
    Join Date
    Apr 2011
    Location
    Santa Cruz, California
    Posts
    586
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Quote Originally Posted by Jerry_R View Post
    Handy link - wished I had seen that - would have saved me some typing

    Cheers,
    -- Joe

    http://mountainjoe.zenfolio.com/ - excuse the mess

  17. #17
    Not Available
    Join Date
    Jul 2009
    Location
    New York
    Posts
    1,864
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Yeah, the article wasn't entirely clear, so I spent the morning cleaning up the first and last artickes and added more illustrations and images, etc. Definitely needed it. Thanks again for the feedback, guys.

  18. #18
    Super Duper
    Senior Member
    rayyan's Avatar
    Join Date
    Jan 2008
    Posts
    5,887
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Quote Originally Posted by leicashot View Post
    Gotta disagree. Perspective is dependent on focal length as each focal length carries a particular perspective with it.....ok my last post on GetDPI, cheers

    K
    Gotta disagree. But what do I know. Even with my lux 50mm asph I take ' lousy ' pictures. Maybe I should try removing the lens cap.
    But it might get dust on my shiny lens.

    Cheers.

  19. #19
    Senior Member mjm6's Avatar
    Join Date
    Jul 2009
    Location
    Sacramento, CA
    Posts
    526
    Post Thanks / Like
    Images
    15

    Re: In-Depth Articles on Lenses

    Quote Originally Posted by mountainjoe View Post
    Handy link - wished I had seen that - would have saved me some typing

    Cheers,

    Mountainjoe is correct...

    We've had this discussion before in this forum...

    http://forum.getdpi.com/forum/showth...eferrerid=3085

    Look at the posts about 1/2 of the way through the thread. I provided images that prove that perspective is 100% dependent on the geometry of the situation, and not on the focal length of the lens.


    ---Michael
    a7r, a7rII, FE 16-35, FE 24-70GM, FE 70-200, Loxia 21mm, 35mm, 50mm

  20. #20
    Not Available
    Join Date
    Jul 2009
    Location
    New York
    Posts
    1,864
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Slowly started updating the lens reviews; going to be adding a lot more detail, samples, etc. Just a matter of finding the time. Started with the Zeiss C Sonnar T* 1,5/50 ZM review by adding a bit under the focus shift section, added MTF and other curves... I still plan to do an actual focus shift, vignetting and sharpness tests w/results (M8 and film/M9)... You can click on the "6/4" of the elements/groups and it'll pop up a layout of the internals.

    Then do all the rest...

  21. #21
    Not Available
    Join Date
    Jul 2009
    Location
    New York
    Posts
    1,864
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Vignetting tests and "Further Research" sections added to most lens reviews, along with "Coding for Digital Ms."

    Getting there! If I wasn't leaving for Germany in a few days, I'd have some time this coming weekend to add additional tests, but alas - authentic Bier and Schnitzel wait for no man!

  22. #22
    Member
    Join Date
    Apr 2009
    Location
    Vancouver, BC
    Posts
    221
    Post Thanks / Like
    Images
    1

    Re: In-Depth Articles on Lenses

    Had a quick read of the first article.

    There's a small error near the end in the naming section:

    The lens is a "APO -Telyt-M 135mm f/3.4 ASPH ", not f/4.

    I'm sure you know this, but the Cosina way of naming Voigtländer lenses is based on the old Voigtländer way of naming things, with Ultrons being around f/2, Noktons faster and Skopars and Color Skopars being slower, with the latter being better optimized for colour, ie, less magnification variation due to spectral differences. Heliars were typically long focal length lenses with larger amounts of spherical aberration to allow adjustment of sharpness and especially contrast of fine detail by varying the aperture. A high bokeh quality was designed into these lenses.

  23. #23
    Not Available
    Join Date
    Jul 2009
    Location
    New York
    Posts
    1,864
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    Aha! Thank you, I fixed that typo. Must've had the Tele-Elmar-M on the brain or something.

    Interesting info on the Voigtländer naming, and yes - not entirely new stuff there. The Ultrons and Noktons are fairly obvious - as are the Heliars (which I believe are Tessar variants).

    Though I don't know that I'd say Color Skopars are "optimized for color." Every lens is optimized for color, even old lenses that, at the time - could only record on black and white film (since that's all they had back then). Black and white in some ways is actually more demanding than color.

  24. #24
    Not Available
    Join Date
    Jul 2009
    Location
    New York
    Posts
    1,864
    Post Thanks / Like

    Re: In-Depth Articles on Lenses

    I added a new review over the weekend; the Zeiss Biogon T* 2/35 ZM and added some preliminary sharpness tests and additional sample images thread links to existing reviews. Wrote up an article just today for the heck of it - Breaking the Photographic Rut.

    I'm looking forward to improved sharpness testing (both charts and real world) and reviewing the next lens - I'm thinking the Zeiss Biogon T* 2,8/25 or Planar T* 2/50 ZMs. Love those lenses.

    If ya haven't been by in a while, come check it out. It's really coming along, I think.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •