sigma 30mm f/1.4 background blur

[richard_bach]

hello everyone,

 

I am currently looking for a fast normal prime for my 20d. I am seriously condsidering the Sigma, but

haven't had the chance to try it out.

 

Even at f/1.4, is 30mm too wide to allow shallow depth of field? my main purpose besides low light would

be shallow depth of field applications. how well would the sigma work for this?

 

any other general comments on the lens are appreciated, as every resource on the lens has had a different

opinion on it.

 

Thanks in advance.

Richard

[Stock-Photos]

http://www.fredmiranda.com/reviews/showproduct.php?product=320&sort=7&cat=38&page=1

[zigzag]

Place your camera type and distances into the calculator <a href="http://www.cambridgeincolour.com/tutorials/depth-of-field.htm">[here]</a> and see what you think about DOF at f/1.4.

 

I think at f/1.4 you will see the DOF is very shallow.

 

Incidentally, then just change to a 24mm lens and a 50mm and see how the DOF changes - in which direction does it go as the lens becomes wider?

[taner]

I am really enjoying mine so far:

 

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00NnwI<div></div>

[William Michael]

>>> Even at f/1.4, is 30mm too wide to allow shallow depth of field? my main purpose besides low light would be shallow depth of field applications. how well would the sigma work for this? <<<

 

No, the 30mm will `allow shallow DoF`: it depends on one`s interpretation of `shallow` and how far away the subject is . . .

 

At F1.4 on a 20D (CoC = 0.1995)

 

Subject Distance 3 ft DoF = 2 inches

 

SD 6 ft, DoF = 8 inches

 

SD 9 ft, DoF = 18 inches

 

SD 12ft, DoF = 32 inches (nearly 3 ft)

 

SD 15ft, DoF = 51 inches (nearly 4.5 ft)

 

I would refer to 2 inches and 8 inches as a `shallow` DoF, but NOT 18 inches: your interpretations might be different.

 

A 50mm (f1.8 or F1.4) would be handy to have as a standby, in your coat pocket, IMO.

 

WW

[michaelkh]

My experience with it suggests that the depth of field on a DX sized sensor is roughly

equivalent to about f/2.4 with my 50mm f/1.8 on film.

 

There will be slightly more depth of field on a canon APS-C sensor as I understand it, but

you will get reasonably shallow depth of field, yes.

 

I think carrying a 50mm f/1.8 or f/1.4 as well is an excellent idea.

 

As for general comments, I like the lens a lot on my Fuji S2, but then I'm not a lens

marque purist, nor am I overly given to fine measuring of things. It might really be as

rubbish as some people suggest, and it'd be fine with me as long as my results were OK.