Re: Canon 17/40 f/4L

"Eric Hocking" <(E-Mail Removed)> wrote in message
news:bdctv1$1hp$(E-Mail Removed)...
<snip>
> Well, in that 4x4ft box the original poster was talking about, my back of
a
> cigarette packet calculations gives the Canon 17mm an horizontal fov of
27in
> and the Sigma 15mm an horizontal fov of 43in at a distance of 3ft (I'm
> allowing 1ft for a "fathead" and the camera). So, it would appear that in
> the situation described, the Sigma will capture 16in more of the scene in
> the horizontal - that's potentially the difference only capturing a son
and
> daughter and chopping out another son/daughter from the photo.
>
> The Sigma 17mm gives an horizontal 38in fov - 11ins better than the Canon.
>
> Again the above is back of the envelope calcs - anyone feel free to
correct
> them, but it's good enough for government work in my book.

Let me be the first to correct. The above is based on 1/2 of the chord, so
I believe the dimensions of the view are closer to:

Canon 17mm: 54x36in
Sigma 15mm: 86x57in
Sigma 17mm: 76x51in

So perhaps the measurement is only signficant in this case in the *vertical*

And then again, my maths could *still* be wrong!

>
> --
> Eric Hocking
> "A closed mouth gathers no feet"
> "Ignorance is a renewable resource" P.J.O'Rourke
> REPLACE ".com" with ".co.uk" to reply
> http//www.twofromoz.freeserve.co.uk




Eric Hocking

> Let me be the first to correct. The above is based on 1/2 of the chord,
so
> I believe the dimensions of the view are closer to:
>
> Canon 17mm: 54x36in
> Sigma 15mm: 86x57in
> Sigma 17mm: 76x51in
>
> So perhaps the measurement is only signficant in this case in the
*vertical*
>
> And then again, my maths could *still* be wrong!
>


Your math my be correct, but your input data is more than likely wrong on
the canon 17-40 lens. It should probably be about 104degrees and not
74degrees. I'm not gonna do the math, but you could try it again.

The difference between the two sigmas sounds correct but the canon is (I am
99% sure ) is incorrect.

BillP

How do you get 4 kids and a fat headed photographer into a 4ft square area?
JT

"Eric Hocking" <(E-Mail Removed)> wrote in message
news:bdddgv$5so$(E-Mail Removed)...
> "Eric Hocking" <(E-Mail Removed)> wrote in message
> news:bdctv1$1hp$(E-Mail Removed)...
> <snip>
> > Well, in that 4x4ft box the original poster was talking about, my back
of
> > a cigarette packet calculations gives the Canon 17mm an horizontal fov
of 27in
> > and the Sigma 15mm an horizontal fov of 43in at a distance of 3ft (I'm
> > allowing 1ft for a "fathead" and the camera). So, it would appear that
in
> > the situation described, the Sigma will capture 16in more of the scene
in
> > the horizontal - that's potentially the difference only capturing a son
> > and daughter and chopping out another son/daughter from the photo.
> >

"Auspics" <(E-Mail Removed)> wrote in message
news:rrbLa.550$(E-Mail Removed)...
> How do you get 4 kids and a fat headed photographer into a 4ft square
area?
> JT

Give a 400mm lens to Eric and he will make it a fisheye. It's all in the
math.

"BillP" <(E-Mail Removed)> wrote in message
news:3efc5768$0$9666$(E-Mail Removed) ...
> > Let me be the first to correct. The above is based on 1/2 of the chord,
> so
> > I believe the dimensions of the view are closer to:
> >
> > Canon 17mm: 54x36in
> > Sigma 15mm: 86x57in
> > Sigma 17mm: 76x51in
> >
> > So perhaps the measurement is only signficant in this case in the
> *vertical*
> >
> > And then again, my maths could *still* be wrong!
>
> Your math my be correct, but your input data is more than likely wrong on
> the canon 17-40 lens. It should probably be about 104degrees and not
> 74degrees. I'm not gonna do the math, but you could try it again.
>
> The difference between the two sigmas sounds correct but the canon is (I
am
> 99% sure ) is incorrect.

Yep, shown up by the true specs from the US Canon site.

--
Eric Hocking
"A closed mouth gathers no feet"
"Ignorance is a renewable resource" P.J.O'Rourke
REPLACE ".com" with ".co.uk" to reply
http//www.twofromoz.freeserve.co.uk