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In-Depth Articles on Lenses

Double Negative

Not Available
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... :p

Lens Primer - The Basics

Lens Primer - Creative Controls

Enjoy. :)
 

doug

Well-known member
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.
 

Jerry_R

New member
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.
 

Jerry_R

New member

Moonshine

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

doug

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

Double Negative

Not Available
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...

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. :)

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? :p
 

Double Negative

Not Available
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. :p
 

leicashot

New member
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-forum/leica-m9-forum/191402-should-i-buy-75mm-3.html#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
 

emr

Member
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!
 

Double Negative

Not Available
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. :p

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!
 
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,
 

jeffnesh

Member
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
 

Double Negative

Not Available
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.
 

rayyan

Well-known member
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.
 

mjm6

Member

Double Negative

Not Available
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... :p
 
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