maybe good or bad but thought someone may like to see it.

http://www.pbase.com/sparky14/gallery/300mm_lens_test




.

Pity no Sigma 50-500 Bigma. Interesting the difference at f8 between the Canon 300f2.8 and the f4.

Originally Posted by Humungus maybe good or bad but thought someone may like to see it. http://www.pbase.com/sparky14/gallery/300mm_lens_test .

SO - what's your conclusion 'Gus?

my conclusion:

that's a lot of money right there!!!

actually, real conclusion: I can see why my friend loves his recently aquired Sigma 100-300 f4 so much - the test shots from that one look like some of the best to my untrained eye. AND its a zoom!

a question from me: why is Canon's 300 f2.8 so much bigger than Sigma's 300 f2.8??

Originally Posted by DoctorIt a question from me: why is Canon's 300 f2.8 so much bigger than Sigma's 300 f2.8??

The Canon lens has IS

Originally Posted by pathfinder SO - what's your conclusion 'Gus?

Once you spend a few $K on gear...its all down to the mug holding it !!

Originally Posted by DoctorIt a question from me: why is Canon's 300 f2.8 so much bigger than Sigma's 300 f2.8??

Let me elaborate on my previous answer with the following chart I put together. Note that the IS causes an increase in the lens elemnts and the lens groups.

Canon Sigma
Lens Construction (group)
13 ..... 10
Lens Construction (element)
17 ..... 12
No. of Diaphragm Blades
8 ..... 9
Minimum Aperture
32 ..... 32
Closest Focusing Distance (m)
2.5 ..... 2.5
Filter Diameter (mm) (rear)
52 ..... 46
Maximum Diameter x Length (mm)
128 x 252 ..... 119 x 214
Weight (g)
2,550 ..... 2,400

Originally Posted by DoctorIt my conclusion: that's a lot of money right there!!!

which one is which??????

Originally Posted by Ann McRae which one is which??????

....question! The key is on the same page as the .jpg of the lenses.

Originally Posted by cmr164 Let me elaborate on my previous answer with the following chart I put together. Note that the IS causes an increase in the lens elemnts and the lens groups. Canon Sigma Lens Construction (group) 13 ..... 10 Lens Construction (element) 17 ..... 12 No. of Diaphragm Blades 8 ..... 9 Minimum Aperture 32 ..... 32 Closest Focusing Distance (m) 2.5 ..... 2.5 Filter Diameter (mm) (rear) 52 ..... 46 Maximum Diameter x Length (mm) 128 x 252 ..... 119 x 214 Weight (g) 2,550 ..... 2,400

good call - IS adds elements.

Originally Posted by cmr164 The Canon lens has IS

I don't think IS is reason the Canon lens is larger. The Canon 75-300 IS is no where near as large and it has IS. The 23-135 IS isn't that large. Nor is the 70-200 f2.8 IS L.
I think the reason the Canon 300mm F2.8 IS L is that large is to capture more light. Objective lenses are measured by their diameter and Canons Objective is significantly larger eg: it gathers more light. That is inescapable,.

One way to make a lens smaller is to make it f2.9 or f3 and label it f2.8 - pretty close in the film world where 1/3 of a stop is reletively insignificant.

Originally Posted by pathfinder I don't think IS is reason the Canon lens is larger. The Canon 75-300 IS is no where near as large and it has IS. The 23-135 IS isn't that large. Nor is the 70-200 f2.8 IS L. I think the reason the Canon 300mm F2.8 IS L is that large is to capture more light. Objective lenses are measured by their diameter and Canons Objective is significantly larger eg: it gathers more light. That is inescapable,. One way to make a lens smaller is to make it f2.9 or f3 and label it f2.8 - pretty close in the film world where 1/3 of a stop is reletively insignificant.

Giggle....

Ok lets compare the Canon 28-200 f3.5-5.6 with the 28-135 f3.5-5.6. Clearly the 2nd lens with its shorter FL range should be physically smaller in length with a optical length of 135mm vs 200mm and in diameter because f5.6 at 135mm is a smaller diameter than f5.6 at 200mm.

The reality is that the IS lens is longer larger diameter and heavier than the 28-200mm lens.

28-135IS ..... 28-200 without IS
Lens Construction (group)
..... 12 ..... 12
Lens Construction (element)
..... 16 ..... 16
No. of Diaphragm Blades
..... 6 ..... 6
Minimum Aperture
..... 22-36 ..... 22-36
Closest Focusing Distance (m)
..... 0.5 ..... 0.45
Filter Diameter (mm)
..... 72 ..... 72
Maximum Diameter x Length (mm)
..... 78x97 ..... 78.4x89.6
Weight (g)
..... 549 ..... 495

[Humungus throws hands into the air & slowly walks out of the room backwards..muttering]


"Hey...i don't want any trouble"

Originally Posted by cmr164 Giggle.... Ok lets compare the Canon 28-200 f3.5-5.6 with the 28-135 f3.5-5.6. Clearly the 2nd lens with its shorter FL range should be physically smaller in length with a optical length of 135mm vs 200mm and in diameter because f5.6 at 135mm is a smaller diameter than f5.6 at 200mm. The reality is that the IS lens is longer larger diameter and heavier than the 28-200mm lens. 28-135IS ..... 28-200 without IS Lens Construction (group) ..... 12 ..... 12 Lens Construction (element) ..... 16 ..... 16 No. of Diaphragm Blades ..... 6 ..... 6 Minimum Aperture ..... 22-36 ..... 22-36 Closest Focusing Distance (m) ..... 0.5 ..... 0.45 Filter Diameter (mm) ..... 72 ..... 72 Maximum Diameter x Length (mm) ..... 78x97 ..... 78.4x89.6 Weight (g) ..... 549 ..... 495

Interesting Charles - the objective lenses diameters are the same - maybe for zoom lenses the objective lens diameter has other variables than just aperature. But for a prime lens, is it not true that the diameter of the front element is the major factor in the maximum f stop since f stops are a ratio of focal length to diameter?

Time Life Library of Photography : The f stop number for any aperature is arrived at by dividing the diameter of the aperature into the focal length of the lens. Hence f2.8=300/X in mm Hence X=300/2.8 = 107 mm
I just picked up a centimeter ruler and measured the diameter of the front element of my Canon 300mmF2.8 - guess what It is 10.7 cm or 107mm. I don't think that is an accident.

Like I said earlier - since the aperature number is a direct relationship to the true focal length, I do not understand how the other lenses can be smaller in diameter - unless they are a shorter focal length or they are not a true f2.8 If a lens was a 285 mm focal length and f3.0 ( rather than a true f2.8) then the front lens would only need to be 95mm in diameter - one full centimeter smaller in diameter and 95 Squared =9025 and 107 squared=11449 9025/1449=78% A lens that is only 80% of the area of a different lens will be cheaper to make than the larger lense all things being equal - won't it?
Is there something here I am confused about Charles? I am not an optical engineer, but I think the math speaks for itself.

You said the Canon lens was larger because of IS and the added elements and compexity of IS - The lens barrel may be bigger as you say. For me, when I said the Canon lens was bigger, I meant in diameter - the front lens element is larger in diameter, and hence, area and hence, admits more light because of its larger optical aperature. IS had nothing to do with the size of the front lens element.

Anyway this has been an interesting discsussion and I think I learned something - I KNOW the diameter a front lens element must be for a given aperature for a given focal length.

Originally Posted by pathfinder Interesting Charles - the objective lenses diameters are the same - maybe for zoom lenses the objective lens diameter has other variables than just aperature. But for a prime lens, is it not true that the diameter of the front element is the major factor in the maximum f stop since f stops are a ratio of focal length to diameter?.... Anyway this has been an interesting discsussion and I think I learned something - I KNOW the diameter a front lens element must be for a given aperature for a given focal length.

All the math is correct and the diameter of the objective and the FL do create a hard limit on the f-stop but there are factors that can make that limit effectively less (never more). On an IS equipped lens the optical path is moving quite lterally and inorder to do that there is a virtual objective size that is smaller that the physical objective size to give jiggle room for the IS. I similar effect ecists with fixed max aperture zooms. The 16-35 f2.8L clearly is not getting the full benefit of the fron objective or it would have to have a numerically lower f-stop at 16mm than at 35mm