Canon Lens RumorsCanon Patents

Canon EF-S 17-55 f/2 IS – Patent

EF-S 17-55 Replacement Coming?
A patent has been discovered showing the existence of an EF-S 17-55 f/2 IS lens.

Canon EF-S 17-55 f/2 IS
Canon EF-S 17-55 f/2 IS

Canon EF-S 17-55 f/2 IS
Patent Publication No. 2010-14866
Published 2010/01/21
Filing Date: 2008/07/02

Example 1
Focal length f = 17.50 ~ 53.05mm
Brightness F = 2.0
Focus back 34.90 ~ 48.26mm

Example 2
Focal length f = 17.50 ~ 52.36mm
Brightness F = 1.8
Back Focus 34.15 ~ 45.06mm

General
Zoom is easy to increase the rate
Increase the amount of movement of the lens
But more aberration
Large diameter is easily
To compensate by increasing the number of lens aberration
But heavier
Patent literature
Placement of the lens to optimize the refractive index
Aspheric lenses

From Here: http://egami.blog.so-net.ne.jp/2010-02-08#more

CR’s Take
I’ve looked quickly, but I haven’t been able to find the actual patent anywhere. Can anyone else?

Thanks Justin

74 responses to “Canon EF-S 17-55 f/2 IS – Patent”

  1. I’d just like to correct jo-1 and Fred. f2.0 on an EF-S lens is FF equivalent of f2.0. Your point is only true for an EF lens used on a crop sensor lens. E.g f2.8 would have a shallower depth of field on a FF than a crop. The 17-55mm f2.8 IS WILL have the same DOF as a 24-70 on a FF. This is because EF-S lenses have the rear element moved towards the sensor. This means that although it’s labelled as a 17-55mm (because that’s the EF equivalent to achieve the same angle of view on a crop body), it is actually a 27 to 88 mm design with a smaller image circle. Therefore at a comparable focal length, marked 50mm on a 24-70mm and marked 31mm on the EF-S, both at f2.8, the DOF WILL be the same. Only if the 24-70 was used on both at 31mm and 50mm would you see a difference in DOF.

    Also, as an owner of a 17-55, amazing but not as much colour and contrast as you’d expect from an L.

  2. No it is not. It is a 17-55 with a smaller image circle (than an EF lens of the same focal length range) that replicates the fov of a FF 27-88. The focal length is what is printed on it.

    If it was a 27-88 focal length then the fov would be even narrower. Just put a 17-40 on your crop camera and view at 17mm then put your 17-55 on at 17mm, fov is the same.

Leave a Reply

Your email address will not be published. Required fields are marked *