Reply to thread

Message

<blockquote data-quote="WayneF" data-source="post: 191525" data-attributes="member: 12496">Well, focal length of a lens (and sensor size) determines its angle of view.&nbsp; The numbers are not a convenient working tool, but still the numbers are:Speaking of horizonal width angle of view:DX camera:&nbsp;&nbsp; 60mm lens has 22 degree view,&nbsp; 120 mm (double) has 11 degrees (half).&nbsp; 105mm has 13 degrees.FX camera:&nbsp;&nbsp; 60mm lens has 33 degree view,&nbsp; 120 mm (double) has 17 degrees (half).&nbsp; 105mm has 20 degrees.This angle is simple &quot;similar triangles&quot; = 2 arc tan(radius / distance).&nbsp; The angle is same in front of lens (subject distance and subject dimension) as it is in back of lens (focal length and sensor size).&nbsp; At 1:1, the distance in front of lens is same as distance behind it.&nbsp; Two complications, the focal length increases as the lens is racked out forward to do 1:1.&nbsp; And we really do not know the point inside the lens where this is measured from - but it is all ballpark true.FX is 1.5x DX.&nbsp; So, to get the same viewing angle, the numbers show we must stand 1.5x closer with FX than with DX, if using same lens.&nbsp; The same lens is the same lens, so the only reason FX has wider view is simply because the FX sensor is bigger, it captures a wider view, but the DX sensor crops that view smaller.All these macro lenses will give a 1:1 size view.&nbsp; 1:1 size would be (for example), when a picture of a small coin would be the same actual size ON THE FILM as the coin is in real life.&nbsp; Means that for digital too, but we cannot remove the digital sensor and look at it, so it seems more clear about film. Same thing though.I don't know if 1:1 (extreme closeup) would be important to you or not.&nbsp; But they will all do 1:1.&nbsp; However, in doing it, the 60 mm might be within 2 inches of the subject, where the 105 mm might be back 6 or 7 inches from subject.&nbsp; We feel more comfortable working back at a few inches, the camera does not block the light for one thing.But if larger work than 1:1, if for example we want to include a subject area of maybe 18 inches in the view... then the 105 mm is a strong telephoto (160mm &quot;view&quot; on DX), which means it must stand back maybe 8 feet, which becomes inconvenient.&nbsp; 60 mm would be more like 3 or 4 feet, more friendly working.</blockquote>

[QUOTE="WayneF, post: 191525, member: 12496"] Well, focal length of a lens (and sensor size) determines its angle of view. The numbers are not a convenient working tool, but still the numbers are: Speaking of horizonal width angle of view: DX camera: 60mm lens has 22 degree view, 120 mm (double) has 11 degrees (half). 105mm has 13 degrees. FX camera: 60mm lens has 33 degree view, 120 mm (double) has 17 degrees (half). 105mm has 20 degrees. This angle is simple "similar triangles" = 2 arc tan(radius / distance). The angle is same in front of lens (subject distance and subject dimension) as it is in back of lens (focal length and sensor size). At 1:1, the distance in front of lens is same as distance behind it. Two complications, the focal length increases as the lens is racked out forward to do 1:1. And we really do not know the point inside the lens where this is measured from - but it is all ballpark true. FX is 1.5x DX. So, to get the same viewing angle, the numbers show we must stand 1.5x closer with FX than with DX, if using same lens. The same lens is the same lens, so the only reason FX has wider view is simply because the FX sensor is bigger, it captures a wider view, but the DX sensor crops that view smaller. All these macro lenses will give a 1:1 size view. 1:1 size would be (for example), when a picture of a small coin would be the same actual size ON THE FILM as the coin is in real life. Means that for digital too, but we cannot remove the digital sensor and look at it, so it seems more clear about film. Same thing though. I don't know if 1:1 (extreme closeup) would be important to you or not. But they will all do 1:1. However, in doing it, the 60 mm might be within 2 inches of the subject, where the 105 mm might be back 6 or 7 inches from subject. We feel more comfortable working back at a few inches, the camera does not block the light for one thing. But if larger work than 1:1, if for example we want to include a subject area of maybe 18 inches in the view... then the 105 mm is a strong telephoto (160mm "view" on DX), which means it must stand back maybe 8 feet, which becomes inconvenient. 60 mm would be more like 3 or 4 feet, more friendly working. [/QUOTE]

Verification