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Archive 2007 · Reverse mounting info. Topic Name Change.
  
 
Tom Hicks
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p.4 #1 · p.4 #1 · Reverse mounting info. Topic Name Change.


Ok we have taken two different lens one a 100mm normal lens and the other 100mm macro lens , both at the min focus distance , both producing different magnification .

Let go back, taking the same set up, but putting the 100mm lenses at infinity focus.

The first image is with the 100-300 set at 100mm and infinity focus, note there is no change in image size as when the same lens was focus at min focus dist.







Jan 11, 2008 at 10:06 PM
Tom Hicks
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p.4 #2 · p.4 #2 · Reverse mounting info. Topic Name Change.


Now for the 100mm macro lens at infinity . Remember EXIF is intact.







Jan 11, 2008 at 10:07 PM
Tom Hicks
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p.4 #3 · p.4 #3 · Reverse mounting info. Topic Name Change.


Now this last images is with the 100-300 zoomed in to the point where I got the same image size as with the 100mm macro at min focus distance. Note in the EXIF data. it comes out to be 165mm, that's pretty close to the 1.6 crop . 165 divided x 50 = 3.3 to 1









Jan 11, 2008 at 10:10 PM
 

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Dalantech
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p.4 #4 · p.4 #4 · Reverse mounting info. Topic Name Change.


Tom Hicks wrote:
Yes, and taking in account the crop of the camera 3 to1


I think what Tom was trying to say is that you'd need to shoot at 3 to 1 with a full frame camera to get a similar screen or print size -and not that the magnification changed.

It's been a long running discussion here and on other web sites as to what's really happening with the smaller than full frame sensors. Some people have even used the term "print magnification" which I can't stand because it implies that the image is magnified when it's not.

The crop factor of the smaller than full frame sensors is just that -a crop. No different that the cropping tool in Photoshop and there is no magic in it.

But when you shoot with a full frame camera and view the image on a computer screen (or print it) the subject will appear smaller because the computer (or the printer) is going to size the overall image to fit the medium that it's displayed on. The magnification hasn't changed but it sure looks like it has...

Maybe we should adopt terms like "screen crop factor" and "print crop factor" so that we can keep things straight?...



Jan 11, 2008 at 10:40 PM
quine
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p.4 #5 · p.4 #5 · Reverse mounting info. Topic Name Change.


I started experimenting with lens reversal a week or so ago. The best result I got is this shot of a quarter:

http://andrew.cmu.edu/user/djwang/photos/fm/_IMG_0712_quarter_200_28_smaller.jpg

It was shot with reversed 28mm held in front of 200mm, which I think is approximately 7:1 (I could be entirely wrong on this, but I think I'm in the ballpark).



Jan 12, 2008 at 12:29 PM
Tom Hicks
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p.4 #6 · p.4 #6 · Reverse mounting info. Topic Name Change.


I will unstick this thread in a few days , so read it while you can .


Jan 19, 2008 at 09:29 PM
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