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Optics Theory - This forum is aimed towards the TECHNICAL side of photographic OPTICS THEORY. There will be some overlap by camera/manufacturer, but this forum is for the heavy duty tech discussions. This is NOT the place to discuss a specific lens or lens line, do that in the appropriate forum. This is the forum to discuss optics or lenses in general, to learn about the tech behind the lenses and images. IF you have a question about a specific lens, post it in the forum about that type of camera, NOT HERE.

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Old 11-21-2010   #51
gekopaca
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When I shoot with R-D1 (X1,5 factor) I use very often 12 and 15mm (eq. 18 and 21mm) and 35 and 50mm (eq. 50 and 75mm) but I don't like my 28mm (eq 40mm) : I can't find a good frame with it, don't like the pictures I make with…
It's very stange, because with my Panasonic GH1 (X2 factor) I love my 20mm (eq.40mm) and I feel it really easy to frame.
Is it because one is Rf and the other one VF? I don't know.
About 14mm with GH1 (eq. 28mm) I feel it too "wise"; I prefer eq. 24mm or even 21mm (doesn't still exists for this camera).
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Old 11-21-2010   #52
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Quote:
Originally Posted by rondo View Post
This was supposed to be a technical discussion over the differences, and it ended up being "I like x better than y / horses for courses" kind of replies which the photo forums is full of...Too bad no one with the two lenses volunteered to do a simple test. Thanks anyway.
Man, just go to a store and try the two for yourself if that is all you wanted.
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Old 11-21-2010   #53
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When I said I didn't have access to it, this would include camera stores too, I live in an other part of the world, where people order things from foreign countries-and are stuck with it. I should tell you that there are few fancy camera stores here (few of them lets you touch cameras, and when they do never with batteries in them-and forget about trying them with your flashdisks)
No one's problem other than mine of course...
In one of the posts above, I did volunteer to do the annoying and time consuming part of it, which must have escaped your attention.
What I requested was two photos with 28 and a 35 from the very same point, and share it here: I will do the necessary adjustment for resizing and overlapping. A digicam with a step zoom would have done it.
I know I was cordial and kind when I requested the help. I like RFF, because people are kind and helpful here, few negative replies won't change my mind.
Ready to take the blame: I guess I wasn't clear about it in my opening post, but not a particularly long thread...I mentioned it few posts later.
http://www.rangefinderforum.com/foru...0&postcount=43

Thanks again.

Last edited by rondo : 11-21-2010 at 05:58.
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Old 11-21-2010   #54
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When you take a tripod, take a 28mm photo (a), then a second 35mm photo (b) from the same point and at the same f-stop, the only (minuscule) differences between (a) cropped by 35/28=1.25 and (b) will be due to the specific lenses you use. Meaning, to do your "test", just take any 28mm photo from flickr and crop it in PS. Voila.
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Old 11-21-2010   #55
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Do you have consumer electronics stores in your area? If so, they should have the Canon S90/95 which allows you to choose precise focal lengths with the dial around the lens barrel. This should help you.
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Old 11-21-2010   #56
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Quote:
Originally Posted by ferider View Post
Meaning, to do your "test", just take any 28mm photo from flickr and crop it in PS. Voila.
So simple yet I would have never thought of it.
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Old 11-21-2010   #57
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Like this. Imagine one was taken by the CV 28/3.5 Color Skopar at around f5.6 or so (which it was), and the other by the 35/2.5 at the same f-stop (very similar lens in signature).
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Old 11-21-2010   #58
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Quote:
Originally Posted by ferider View Post
When you take a tripod, take a 28mm photo (a), then a second 35mm photo (b) from the same point and at the same f-stop, the only (minuscule) differences between (a) cropped by 35/28=1.25 and (b) will be due to the specific lenses you use. Meaning, to do your "test", just take any 28mm photo from flickr and crop it in PS. Voila.
Ferider,
thanks, but not following you, I'm afraid...I don't have the lenses, that's why I was asking...It is not that I am lazy to do it on my own.
Regarding cropping any 28 mm image from flickr: That's exactly what I am trying to see: is it the same thing or there are other lens characteristics that would change the simple math. I have a fixed lens 28 mm digicam. So I don't need flickr to implement your test.
What you are claiming is that, the image I posted at the opening post is correct. that it is simply a view angle difference. Many argued otherwise...
Thanks again,
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Old 11-21-2010   #59
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When people begin to treat focal lengths as holy objects that one must conform to, they forget that the famous focal lengths such as 28/35/50/75 were simply "averages" of the best "compromise" for a focal length in a time when zoom lenses were not feasible yet.

Last edited by ebino : 11-21-2010 at 06:20.
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Old 11-21-2010   #60
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Ferider,
I think distance of the object you are photographing is a factor here. In a landscape shot, I assume you will be right.
But if you are composing something few meters away from you, the difference will be more than angle of view.
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Old 11-21-2010   #61
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Quote:
Originally Posted by rondo View Post
Ferider,
thanks, but not following you, I'm afraid...I don't have the lenses, that's why I was asking...It is not that I am lazy to do it on my own.
Regarding cropping any 28 mm image from flickr: That's exactly what I am trying to see: is it the same thing or there are other lens characteristics that would change the simple math. I have a fixed lens 28 mm digicam. So I don't need flickr to implement your test.
What you are claiming is that, the image I posted at the opening post is correct. that it is simply a view angle difference. Many argued otherwise...
Thanks again,
It is correct for well corrected lenses; say for instance you compare a 35/2 ASPH and 28/2 ASPH Summicron: you will be hard pressed to find any difference between 35 and cropped 28 picture. Of course, if one lens has more distortion than the other, there might be more difference.

Quote:
Originally Posted by rondo View Post
Ferider,
I think distance of the object you are photographing is a factor here. In a landscape shot, I assume you will be right.
But if you are composing something few meters away from you, the difference will be more than angle of view.
As long as your camera location is the same, the difference is only the angle of view. I can look for text book references if you need.

Best,

Roland.
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Last edited by ferider : 11-21-2010 at 06:25.
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Old 11-21-2010   #62
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Here is what a people shot would look like, at f2 and about a meter distance.
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Old 11-21-2010   #63
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Quote:
Originally Posted by ferider View Post
It is correct for well corrected lenses; say for instance you compare a 35/2 ASPH and 28/2 ASPH Summicron: you will be hard pressed to find any difference between 35 and cropped 28 picture. Of course, if one lens has more distortion than the other, there might be more difference.
This is an interesting point. I guess it makes sense to do the comparison with high-end optics, not crappy zoom digicams. Barrel distortion and perspective are two different things.


[/quote] I can look for text book references if you need.[/quote]

Only if you have time, or a link to a website would do. I looked up a bit before posting here, but couldn't find anything.
Thanks again.
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Old 11-21-2010   #64
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Roland, Wow, did you actually take two pictures here, or just cropped a 28?
edit: looking closely, you just cropped it, I think...

Last edited by rondo : 11-21-2010 at 06:43.
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Old 11-21-2010   #65
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Another way of putting what you said:
A 35 mm with m8, will give exactly same results as 50 mm (52 to be exact) with m9.
I assume that has been the experience of those who used both...The angle of view will be the same for sure, and no other optical difference?
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Old 11-21-2010   #66
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At the same camera distance - yes.

My photos above are 28mm photos that I cropped for you.

There are lots of references: http://www.luminous-landscape.com/tu..._lengths.shtml, for example, or for a good text-book, "The Ansel Adams Guide, Book 1, by John P. Schaefer, Chapter 3 - Lenses and Accessories". Maybe Roger can chime in with another on-line reference.

Roland.
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Old 11-21-2010   #67
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Roland, All this psychological difference mumbo-jumbo goes to trash, if this is indeed the case. I am ready to take your word on that. I think you made a good point by differentiating good lenses from bad ones, i think that's the major difference here. And as the lenses get wider optical imperfections are more common.
I learned something from this thread. Thanks...In the future if I have access to both lenses I will try to "satisfy my curiosity" as someone above has put it...Rest assured, I will come and share here my own findings, in case someone else is curious...1500 views on this thread makes me think that it wasn't exactly selfish to ask the question.

Thanks for the links.
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Old 11-21-2010   #68
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When taken from the same camera position, Roland's photo of the girl shows the difference in the field of view of the 2 lenses.

To more completely see the difference in the 2 focal lengths, one needs to do something else: change camera position when changing from one focal length to the other, so that a foreground element is the same size in both photos. That way one can see the difference in perspective of these 2 focal lengths. IMO, this is the most important difference between the 2 focal lengths. One can not see this by simply cropping a 28mm photo to a 35mm field of view. The 28mm lens will show more airy-ness and give the impression of a bigger space between foreground and background elements.

This isn't psychological mumbo jumbo, but it is a little more complex and difficult for some to understand than the simple cropping exercise that demonstrates only the difference in field of view and not the perspective rendering differences of 2 focal lengths.
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Last edited by FrankS : 11-21-2010 at 07:30.
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Old 11-21-2010   #69
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No problem, Rondo. For well corrected RF lenses, there really are only the following practical differences:

1) Compared to 35, you cann't get as "close" with a 28. On Leica, typically, 0.7m for both.
2) Compared to 28, you cann't get as "wide" with a 35. Important in-doors, with your back against a wall and for infinity landscapes.
3) Speed/Size: my fastest 35 is f1.4. An LTM/M-mount 28/1.4 does not exist. On the other hand, my 28/1.9 is much bigger than my 35/1.4.

And rest assured, more mumbo jumbo will be added to this thread

Cheers,

Roland.
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Last edited by ferider : 11-21-2010 at 07:39.
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Old 11-21-2010   #70
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Quote:
Originally Posted by FrankS View Post
When taken from the same camera position, Roland's photo of the girl shows the difference in the field of view of the 2 lenses.

To more completely see the difference in the 2 focal lengths, one needs to do something else: change camera position when changing from one focal length to the other, so that a foreground element is the same size in both photos. That way one can see the difference in perspective of these 2 focal lengths. IMO, this is the most important difference between the 2 focal lengths. One can not see this by simply cropping a 28mm photo to a 35mm field of view. The 28mm lens will show more airy-ness and give the impression of a bigger space between foreground and background elements.

This isn't psychological mumbo jumbo, but it is a little more complex and difficult for some to understand than the simple cropping exercise that demonstrates only the difference in field of view and not the perspective rendering differences of 2 focal lengths.
Absolutely.

Although many here emphasize that learning photography is easier with prime lenses, this is a case where a digital camera with a standard zoom lens is really vastly superior as a learning tool. Rent or borrow a DSLR with a "kit" zoom, and do as Frank suggests on a variety of subjects with a moderate aperture (say, f/5.6), so that enough background is resolved to see how things change as you change FL and move the camera back and forth. A digital camera is preferred for this exercise because you get instant feedback, and because each capture is marked with EXIF data — so that when you go back and look at these reference photos later, there will be no question about what FL and camera settings were used.

Be systematic. Study the results. Go out and take some pictures with the camera's zoom ring taped at 24, 28, 35, 40, 50mm equivalent. See what you like shooting with. See what produces the best results (you may find that these are not the same).

You'll know which prime(s) you want to shoot with soon enough.
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Old 11-21-2010   #71
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Quote:
Originally Posted by FrankS View Post
This isn't psychological mumbo jumbo, but it is a little more complex and difficult for some to understand than the simple cropping exercise that demonstrates only the difference in field of view and not the perspective rendering differences of 2 focal lengths.
ever seen "vertigo"? here's a clip with a bunch of dolly zooms. pay attention to the table in the scene from "goodfellas".

http://www.youtube.com/watch?v=Y48R6-iIYHs

changing the position of the camera is what changes the perspective. changing focal length merely changes angle of view, which in this case is used to keep the subject matter in the shot at the same magnification.
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Old 11-21-2010   #72
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Yeah, that video is a very good demonstration of this. The camera position changes as the lens zooms to keep the foreground elements the same size. You can see the changes happening in the background rendering.
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Old 11-21-2010   #73
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Quote:
Originally Posted by aizan View Post
ever seen "vertigo"? here's a clip with a bunch of dolly zooms. pay attention to the table in the scene from "goodfellas".

http://www.youtube.com/watch?v=Y48R6-iIYHs

changing the position of the camera is what changes the perspective. changing focal length merely changes angle of view, which in this case is used to keep the subject matter in the shot at the same magnification.
Excellent example, and I think a good way to sum things up. I think almost everyone was saying the very same thing in different terms.
If I have to remind you my first post: I was questioning the accuracy of the nested rectangles to identify different focal lengths, with a stationary camera.
That system is absolutely accurate, as long as the camera is stationary the perspective remains exactly the same no matter which lens one uses.
Period. Of course you get more or less coverage of the scene, depending on the focal length, but the relationship of objects does not change based on the focal length used.-again with stationary camera.

If one aims to achieve the same area of coverage (i.e.composition) with different focal lengths, perspective will differ.
Thank you all, especially to Roland and Frank....
I think all is clear and everyone is happy.
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Old 11-22-2010   #74
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Quote:
Originally Posted by aizan View Post
ever seen "vertigo"? here's a clip with a bunch of dolly zooms. pay attention to the table in the scene from "goodfellas".

http://www.youtube.com/watch?v=Y48R6-iIYHs

changing the position of the camera is what changes the perspective. changing focal length merely changes angle of view, which in this case is used to keep the subject matter in the shot at the same magnification.
Thanks for the great video. Maybe this will make more people unsterstand the relationship between point of view, perspective and focal length, and we won't see anymore those stupid "zoom with your feet" recommendations.

Zooming connot be accomplished by getting closer or further away from the subject, as this would modify the perspective, which isn't the case with using a different focal length from the same point of view.

Cheers!

Abbazz
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Old 11-22-2010   #75
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Quote:
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...won't see anymore those stupid "zoom with your feet" recommendations.
They are not exactly stupid as long as they don't suggest it is the "same thing"
Lack of choices shouldn't stop you to think about what you can capture with a given equipment. Sometimes constrains lead to better results.
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