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-   -   Depth of field (http://www.velocityreviews.com/forums/t409585-depth-of-field.html)

rda 01-01-2005 12:42 PM

Depth of field
 
Another question about the Sigma 20mm 1.8 (I just cannot afford the Canon
17-40L).

If I use f1.8 from a distance of around 20' from my subject would a group
shot be sharp, or would I have to stop down?

Sorry to bother you guys all the time.


Happy New Year !

--
rda
www.rdaphoto.co.uk



Joseph Meehan 01-01-2005 02:55 PM

Re: Depth of field
 
rda wrote:
> Another question about the Sigma 20mm 1.8 (I just cannot afford the
> Canon 17-40L).
>
> If I use f1.8 from a distance of around 20' from my subject would a
> group shot be sharp, or would I have to stop down?
>
> Sorry to bother you guys all the time.
>
>
> Happy New Year !


If they were all the same distance from the lens they should all be in
focus, there are a lot of other factors related to sharpness.

If they were standing one behind the other a couple of feet apart, then
the answer is you would need to stop down.

--
Joseph Meehan

26 + 6 = 1 It's Irish Math



dylan 01-01-2005 04:04 PM

Re: Depth of field
 
any use ? http://www.dofmaster.com/dofjs.html

"rda" <nottellin@secret.net> wrote in message
news:Mdydnew2cYs-B0vcRVnyvA@fireflyuk.net...
> Another question about the Sigma 20mm 1.8 (I just cannot afford the Canon
> 17-40L).
>
> If I use f1.8 from a distance of around 20' from my subject would a group
> shot be sharp, or would I have to stop down?
>
> Sorry to bother you guys all the time.
>
>
> Happy New Year !
>
> --
> rda
> www.rdaphoto.co.uk
>
>




rda 01-01-2005 04:26 PM

Re: Depth of field
 

"dylan" <no@nospam.com> wrote in message
news:cr6hnm$kv$1@news7.svr.pol.co.uk...
> any use ? http://www.dofmaster.com/dofjs.html
>


WOW, great link.

It would seem that for 20' the depth of field would be from 13.2' - 41.2'.

Thanks

--
rda
www.rdaphoto.co.uk - comments welcomed (on the photos, I know the site is
crap)



skroob 01-01-2005 05:54 PM

Re: Depth of field
 
I am looking into this lens myself, and have a question or two for the
group.

I have a D70 with the following lenses (18-70mm 3.5/4.5 DX, 70-300 4/5.6 ED,
28mm 3.5 PC, Sigma 12-24mm 4.5/5.6)

I was looking at adding the Sigma 20mm 1.8 to cover me in low-light
situations where my SB-800 flash would be frowned upon (such as in a
Cathedral).

I should mention at this point that I shoot architecture 95% of the time,
where its important for great sharpness and elimination of depth of field
(not a problem set to infinity focus). However, with this lens, i want to
get into artistic and portrait photography.

Is this a wise choice?

Thanks in advance.


"rda" <nottellin@secret.net> wrote in message
news:Mdydnew2cYs-B0vcRVnyvA@fireflyuk.net...
> Another question about the Sigma 20mm 1.8 (I just cannot afford the Canon
> 17-40L).
>
> If I use f1.8 from a distance of around 20' from my subject would a group
> shot be sharp, or would I have to stop down?
>
> Sorry to bother you guys all the time.
>
>
> Happy New Year !
>
> --
> rda
> www.rdaphoto.co.uk
>
>




rda 01-01-2005 05:58 PM

Re: Depth of field
 

"skroob" <skroob@mpwgfwewe.com> wrote in message
news:gtBBd.36341$kq2.14457@twister.nyc.rr.com...
> I am looking into this lens myself, and have a question or two for the
> group.
>
> I have a D70 with the following lenses (18-70mm 3.5/4.5 DX, 70-300 4/5.6

ED,
> 28mm 3.5 PC, Sigma 12-24mm 4.5/5.6)
>
> I was looking at adding the Sigma 20mm 1.8 to cover me in low-light
> situations where my SB-800 flash would be frowned upon (such as in a
> Cathedral).
>
> I should mention at this point that I shoot architecture 95% of the time,
> where its important for great sharpness and elimination of depth of field
> (not a problem set to infinity focus). However, with this lens, i want to
> get into artistic and portrait photography.
>
> Is this a wise choice?
>


I found a few sample images taken with this lens on pbase.
http://search.pbase.com/search?q=20m...ch+Photos&c=sp

Note, only some are taken with the Sigma.



--
rda
www.rdaphoto.co.uk comments welcome (on the photos, the site is crap)



Bart van der Wolf 01-01-2005 06:29 PM

Re: Depth of field
 

"rda" <nottellin@secret.net> wrote in message
news:Se2dnStxp8zOUkvcRVnyvQ@fireflyuk.net...
>
> "dylan" <no@nospam.com> wrote in message
> news:cr6hnm$kv$1@news7.svr.pol.co.uk...
>> any use ? http://www.dofmaster.com/dofjs.html
>>

>
> WOW, great link.
>
> It would seem that for 20' the depth of field would be from 13.2' -
> 41.2'.


Yes, theoretically in the 14-34 feet range everything would be
perfectly in focus, but I doubt the lens will perform uniformly
throughout the Field of view when used wide open...

Bart



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