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About lenses and f-stops

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noise2day

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I'm still learning about all the technical aspects of photography, so would appreciate your guidance on this.

Many of you have great things to say about the "Canon 17-40 f/4 USM L" lens. Does this mean that this lens is fixed at f/4? If so, I assume this implies you don't have much room to play with depth of field... or is there?

Thanks!

--
noise2day
 
Noise,

The F stop mentioned next to a lense description is the WIDEST F stop that lens will open up to. It has all the other f stops closing down so yes you do have room to play with.
Pete
noise2day said:
I'm still learning about all the technical aspects of photography,
so would appreciate your guidance on this.

Many of you have great things to say about the "Canon 17-40 f/4 USM
L" lens. Does this mean that this lens is fixed at f/4? If so, I
assume this implies you don't have much room to play with depth of
field... or is there?

Thanks!

--
noise2day
Click to expand...
 
When listed in the name of a lense the f value is always the maximum.

So in this case the maximum aperture of this lense is f/4, I believe the minimum aperture on this lense is f/22 but I could be wrong.

Cheers
Steve
noise2day said:
I'm still learning about all the technical aspects of photography,
so would appreciate your guidance on this.

Many of you have great things to say about the "Canon 17-40 f/4 USM
L" lens. Does this mean that this lens is fixed at f/4? If so, I
assume this implies you don't have much room to play with depth of
field... or is there?

Thanks!

--
noise2day
Click to expand...
--
http://www.pbase.com/hangman/galleries
 
Pete La said:
Noise,
The F stop mentioned next to a lense description is the WIDEST F
stop that lens will open up to. It has all the other f stops
closing down so yes you do have room to play with.
Pete
Click to expand...
What does it mean when a lens says "f/3.5-5.6", such as with the kit lens "Canon EF-S 18-55mm f/3.5-5.6"?

Thanks!

--
noise2day
 
Yup fixed at f/4. Room to play with DOF??? Well that depends on what your doing. The background blur is dependent on your distance to your subject, your aperature, and the distance to the background. No the DOF will never be as shallow as a 50mm 1.4 or the 16-35mm 2.8 but you have to consider what you plan to use this lens for. If your using it for landscape you will generally want wider dof and will be using f/values of f/8 or higher. For portraits f/4 often works well. Go play with the online dof calulators to see exactly how much room to play you would have... I have a feeling its a bit narrow then you might think. You can still obtain a nice background blur if you set up your shot correctly... but thats more a matter of composition and arrangement than anything else.

-Jordan
noise2day said:
I'm still learning about all the technical aspects of photography,
so would appreciate your guidance on this.

Many of you have great things to say about the "Canon 17-40 f/4 USM
L" lens. Does this mean that this lens is fixed at f/4? If so, I
assume this implies you don't have much room to play with depth of
field... or is there?

Thanks!

--
noise2day
Click to expand...
--
-Jordan
 
Some zoom lenses have different maximum apertures depending on the setting - the f3.5 refers to the maximum available at the widest zoom, and the f5.6 the maximum at the tele end
noise2day said:
Pete La wrote:
What does it mean when a lens says "f/3.5-5.6", such as with the
kit lens "Canon EF-S 18-55mm f/3.5-5.6"?

Thanks!

--
noise2day
Click to expand...
 
when stated 17-40 f4 L it simply means that you can get f4 at 17 and at 40mm. You can also use smaller apertures at all focal lengths f4 is simply the largest aperture you can get with the lens.

if stated 18-55 f4.5-5.6 that means that the largest aperture you can get at 18 mm is f4.5 but as you zoom out the largest aperture changes till you get to 55mm where the largest aperture is 5.6. At all focal lengths you can get smaller apertures. The numbers listed just tell you about the largest apertrure available at various focal lengths.

hope that helps.
Ron
 
noise2day said:
Pete La said:
Noise,
The F stop mentioned next to a lense description is the WIDEST F
stop that lens will open up to. It has all the other f stops
closing down so yes you do have room to play with.
Pete
Click to expand...
What does it mean when a lens says "f/3.5-5.6", such as with the
kit lens "Canon EF-S 18-55mm f/3.5-5.6"?
Click to expand...
This means that at 18mm the maximum aperture will be f/3.5 and when you zoom to 55mm the maximum aperture will be f/5.6. The maximum aperture will be different (between f/3.5 and f/5.6) for different points along the zoom range.

Cheers
Steve
--
http://www.pbase.com/hangman/galleries
 
As most people have correctly pointed out, lenses are described by their focal length in mm and the largest aperture possible. The smallest aperure is also fixed, often f/32. However in the 35mm format you find that few people shoot at f/13 or smaller. DO not shoot at f/16 or higher because your images wil soften up due to diffraction. For an explanation of diffraction and how it affects lenses go to

http://www.normankoren.com/Tutorials/MTF1A.html

It is a rather complicated story.

Yiannis

Show them Amato !!

http://www.pbase.com/ystasino
 
Nope, you are correct minimum aperature is F22....I own this lens...great lens by the way.
SteveP said:
So in this case the maximum aperture of this lense is f/4, I
believe the minimum aperture on this lense is f/22 but I could be
wrong.

Cheers
Steve
noise2day said:
I'm still learning about all the technical aspects of photography,
so would appreciate your guidance on this.

Many of you have great things to say about the "Canon 17-40 f/4 USM
L" lens. Does this mean that this lens is fixed at f/4? If so, I
assume this implies you don't have much room to play with depth of
field... or is there?

Thanks!

--
noise2day
Click to expand...
--
http://www.pbase.com/hangman/galleries
Click to expand...
--
Do what you've always done, Get what you've always gotten.

Visit my gallery at http://www.pbase.com/briguy00
 
Jordan Robbins wrote:
No the DOF will never be as shallow as a 50mm 1.4 or
Jordan Robbins said:
the 16-35mm 2.8 but you have to consider what you plan to use this
lens for.
Click to expand...
The shortest DOF that the 16-35 is capable of, is only about an inch (0.08 ft) shorter than the 17-40mm. A difference that you would not even see in the picture.

The 50mm only has shorter DOF when using f5.6 or wider. (However, it can get very short @ f1.4 though!)

Cheers :)

--
Barry

'He who runs with aggression, walks without dignity' - Samurai Jack
 
Im not sure if I just wrote my response poorly or if I am simply being misinterpreted... thats again not what I ment... I ment that he should consider what he would likely be using the 17-40mm L for and if he would ever really have a need for the wider aperature. I agree with what you said... the primary advantage of the 16-35mm is speed not dof. I guess I rushed too much while writing this seeing that I am at work.

-Jordan
v9 said:
v9 said:
the 16-35mm 2.8 but you have to consider what you plan to use this
lens for.
Click to expand...
The shortest DOF that the 16-35 is capable of, is only about an
inch (0.08 ft) shorter than the 17-40mm. A difference that you
would not even see in the picture.

The 50mm only has shorter DOF when using f5.6 or wider. (However,
it can get very short @ f1.4 though!)

Cheers :)

--
Barry

'He who runs with aggression, walks without dignity' - Samurai Jack
Click to expand...
--
-Jordan
 
Jordan Robbins said:
-Jordan
v9 said:
Jordan Robbins said:
the 16-35mm 2.8 but you have to consider what you plan to use this
lens for.
Click to expand...
The shortest DOF that the 16-35 is capable of, is only about an
inch (0.08 ft) shorter than the 17-40mm. A difference that you
would not even see in the picture.

The 50mm only has shorter DOF when using f5.6 or wider. (However,
it can get very short @ f1.4 though!)

Cheers :)

--
Barry

'He who runs with aggression, walks without dignity' - Samurai Jack
Click to expand...
--
-Jordan
Click to expand...
--
Barry

'He who runs with aggression, walks without dignity' - Samurai Jack
 
Jordan Robbins said:
Oye... I cant win today. :-) I think I need a spellchecker on
this forum.
Click to expand...
Hehe, us glass house denizens are throwing a lotta rocks today :)

I do realize the rest of your post mentioned selecting apertures narrower than f/4, but the original poster used "fixed at f/4" very specifically to mean that f/4 was the only aperture that could be used. When you replied "yup, fixed at f/4" I had to correct you because I was afraid the original poster (noise2day) would be more confused by two respondents saying the aperture was variable but you added terminology which was confusing at best.

No offense intended, I'm sure my best attempts at explaining something here have been riddled with typos or obfuscation. Or both :)

--
Zapped (Austin, TX)
http://www.pbase.com/pricklypear
 
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