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fast glass?



 
 
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  #11  
Old January 9th 06, 05:36 AM posted to rec.photo.digital,rec.photo.digital.slr-systems
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Default fast glass?


"Edwin Pawlowski" wrote in message
m...


2. You can say: "My lens is better than your lens"


Bingo - which is presumably why the manufacturers churn out cheapish lenses
that they know perfectly well are not good enough for such wide aperture
work. People will buy them because of the numbers, rather than the results.






  #12  
Old January 9th 06, 05:46 AM posted to rec.photo.digital,rec.photo.digital.slr-systems
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Default fast glass?


"Bob Williams" wrote in message
news:7Hlwf.8482$jR.1694@fed1read01...


Danny wrote:
everyone seems to want 'fast glass' - f/2.8, 1.7, 1.4, etc, but I'm left
wondering 'why' As most people know, lenses are not at their sharpest
wide open - usually requiring f/7 - 9 (ish) before they attain their
maximum potential.

So why the fuss about 'fast' lenses?, and why pay the huge premiums to
own them? Most of my own lenses are 2.8, with one at 1.7, and one at
1.4 - yet I invariably have to stop down in order to get a nicely sharp
image, which sort of defeats the object of the 'fast glass', doesn't it?

I mean, why pay three times the price for a 'fast' lens, when you only
end up stopping it down? I've got a theory that it's the mania for bright
lenses that's behind a lot of the 'focus fuss' that clogs up the various
forums - perhaps people don't realise that you're just not going to get
the same image quality out of wide open lens and are mistaking 'softness'
for focus issues. Just a thought.

Just think of the "Bragging Rights" that come with the purchase.
Isn't that what life is all about? G



'fraid so. A friend of mine takes a dslr to shoot basic pictures for
websites (the product shots, etc, get farmed out)

His shots are destined to be heavily Photoshopped, Dreamweavered, and
Flashed, and the file size will be drastically reduced for the web. He
could use pretty well any P&S camera - but his clients like to see a
'professional' looking camera and lens because it reassures them.

Life today seems all about how things appear to be, rather than how things
actually are.


  #13  
Old January 9th 06, 05:54 AM posted to rec.photo.digital,rec.photo.digital.slr-systems
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Default fast glass?

Danny wrote:
everyone seems to want 'fast glass' - f/2.8, 1.7, 1.4, etc, but I'm
left wondering 'why' As most people know, lenses are not at their
sharpest wide open - usually requiring f/7 - 9 (ish) before they
attain their maximum potential.

So why the fuss about 'fast' lenses?, and why pay the huge premiums
to own them? Most of my own lenses are 2.8, with one at 1.7, and one
at 1.4 - yet I invariably have to stop down in order to get a nicely
sharp image, which sort of defeats the object of the 'fast glass',
doesn't it?
I mean, why pay three times the price for a 'fast' lens, when you
only end up stopping it down? I've got a theory that it's the mania
for bright lenses that's behind a lot of the 'focus fuss' that clogs
up the various forums - perhaps people don't realise that you're just
not going to get the same image quality out of wide open lens and are
mistaking 'softness' for focus issues. Just a thought.


Some reaons:
1. Intentional limiting depth of field.
2. Bright viewfinder...not only helpful for manual focus, but just plain
easier to use with accuracy.
3. Focus sensors work far better when you double, tripple or quadruple the
light it has to work with prior to actual exosure--regardless of the
aperture you use for that exposure.
4. You can use very fast shutter speeds...which is often worth sacrificing a
bit of lens-based sharpness.


  #14  
Old January 9th 06, 05:58 AM posted to rec.photo.digital,rec.photo.digital.slr-systems
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Default fast glass?


"Charles" wrote in message
...
In article , Danny
wrote:

Why is their always a smart-arse on every Usenet group?


I meant what I said. Read some basic photography books and you will
understand why we need fast glass.



OK. let's try again, shall we?

I'm well aware why some people 'need' fast lenses, and those that do need
them usually buy high quality optics (at high quality prices) that are up to
the job.

My point (perhaps not clearly made) is that the great mass of 'hobby'
photographers are buying cheaper lenses that are unsharp at wide apertures,
simply because an f/2.8 badge on a lens gives it more street cred than an
f/5.6 - even though the cheap ".8 might very well have to be stopped down
past the 'slower' lens in order to get a decently sharp image.

I know - because I've been suckered by the manufacturers as well, and If I
was buying them again I'd be far less impressed by the alleged maximum
aperture, and concentrate on element quality and construction.

btw, sorry for flying off the handle, I just assumed that you were taking
the ****.


  #15  
Old January 9th 06, 06:01 AM posted to rec.photo.digital,rec.photo.digital.slr-systems
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Default fast glass?

Danny wrote:
"Charles" wrote in message
...
In article , Danny
wrote:

Just a thought.


Just a thought. Read a basic book about photography.



Why is their always a smart-arse on every Usenet group? - don't you
have a ****ing job to go to?


It might have been a bit abrupt...but it certainly has a shred of truth to
it, since this is a topic any general photography technique book would cover
in some detail...but I understand your reaction to his less-than-tactful
reply...

For a better answer...see my original reply.
I'm surprized others haven't listed these little items.
They matter.

Ah heck... Here's a RE-post of it (with a bit more added), just in case you
lose your way.


Some reaons:
1. Intentional limiting of/greater control of depth of field.
2. Bright viewfinder...not only helpful for manual focus, but just plain
easier to accurately use in general.
3. Focus sensors work far better when you double, tripple or quadruple the
light it has to work with (which applies to any/every shot, since the focus
mechanism works PRIOR to stopping the bright lens down.
4. You can use very fast shutter speeds...which is often worth sacrificing a
bit of lens-based sharpness.
5. With many camera bodies, certain focus sensors become active ONLY with
lenses that are 2.8 or faster, simply due to the need for greater light
gathering/sensitivity.

All these add up to very good reasons and very legitimate uses for large
aperture lenses.

Ta-da!

-Mark


  #16  
Old January 9th 06, 06:03 AM posted to rec.photo.digital,rec.photo.digital.slr-systems
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Default fast glass?


"MarkČ" mjmorgan(lowest even number wrote in message
news:K_lwf.8788$V.1281@fed1read04...
Danny wrote:
everyone seems to want 'fast glass' - f/2.8, 1.7, 1.4, etc, but I'm
left wondering 'why' As most people know, lenses are not at their
sharpest wide open - usually requiring f/7 - 9 (ish) before they
attain their maximum potential.

So why the fuss about 'fast' lenses?, and why pay the huge premiums
to own them? Most of my own lenses are 2.8, with one at 1.7, and one
at 1.4 - yet I invariably have to stop down in order to get a nicely
sharp image, which sort of defeats the object of the 'fast glass',
doesn't it?
I mean, why pay three times the price for a 'fast' lens, when you
only end up stopping it down? I've got a theory that it's the mania
for bright lenses that's behind a lot of the 'focus fuss' that clogs
up the various forums - perhaps people don't realise that you're just
not going to get the same image quality out of wide open lens and are
mistaking 'softness' for focus issues. Just a thought.


Some reaons:
1. Intentional limiting depth of field.
2. Bright viewfinder...not only helpful for manual focus, but just plain
easier to use with accuracy.
3. Focus sensors work far better when you double, tripple or quadruple the
light it has to work with prior to actual exosure--regardless of the
aperture you use for that exposure.
4. You can use very fast shutter speeds...which is often worth sacrificing
a bit of lens-based sharpness.



Number 3 sounds a viable reason in theory - but it presupposes that the
camera itself doesn't have any A/F issues. I can only say that the Pentax
f/1.4 A/F lenses are not noted for fast focus in low light. In fact, many
slower Pentax lenses are quicker to focus under the same conditions.


  #17  
Old January 9th 06, 06:10 AM posted to rec.photo.digital,rec.photo.digital.slr-systems
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Default fast glass?


"MarkČ" mjmorgan(lowest even number wrote in message
news5mwf.8789$V.3101@fed1read04...
Danny wrote:
"Charles" wrote in message
...
In article , Danny
wrote:

Just a thought.

Just a thought. Read a basic book about photography.



Why is their always a smart-arse on every Usenet group? - don't you
have a ****ing job to go to?


It might have been a bit abrupt...but it certainly has a shred of truth to
it, since this is a topic any general photography technique book would
cover in some detail...but I understand your reaction to his
less-than-tactful reply...

For a better answer...see my original reply.
I'm surprized others haven't listed these little items.
They matter.

Ah heck... Here's a RE-post of it (with a bit more added), just in case
you lose your way.


Some reaons:
1. Intentional limiting of/greater control of depth of field.
2. Bright viewfinder...not only helpful for manual focus, but just plain
easier to accurately use in general.
3. Focus sensors work far better when you double, tripple or quadruple the
light it has to work with (which applies to any/every shot, since the
focus mechanism works PRIOR to stopping the bright lens down.
4. You can use very fast shutter speeds...which is often worth sacrificing
a
bit of lens-based sharpness.
5. With many camera bodies, certain focus sensors become active ONLY with
lenses that are 2.8 or faster, simply due to the need for greater light
gathering/sensitivity.



That last one sounds interesting - are we talking digital bodies here?
Come to that, how *do* you know that an A/F sensor is working properly? - is
there more to it than simply seeing if the relevant focus point lights up? -
I suppose there must be, because an *ist will illuminate all focus points,
even with the lens cap on!.....


  #18  
Old January 9th 06, 06:14 AM posted to rec.photo.digital,rec.photo.digital.slr-systems
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Posts: n/a
Default fast glass?

Danny wrote:
everyone seems to want 'fast glass' - f/2.8, 1.7, 1.4, etc, but I'm left
wondering 'why' As most people know, lenses are not at their sharpest wide
open - usually requiring f/7 - 9 (ish) before they attain their maximum
potential.


The "rule of thumb" as I remember it is that a lens it generally
sharpest at two stops below its largest aperture. For an f/2.8 lens
then, f/5.6 would be your sharpest aperture. For a lens that maxes out
at f/5.6 (like my Canon EF 75-300 at longer zooms) it would be f/11.

But again, that's just a rule of thumb. A lot of other design
parameters can affect exactly where a lens is sharpest.

So why the fuss about 'fast' lenses?,


Mostly, in order to get faster shutter speeds, which is why they're
called "fast" lenses.

Also useful if you want LESS depth of field, in order to draw the eye to
the subject and reduce a distracting the background.

and why pay the huge premiums to own
them? Most of my own lenses are 2.8, with one at 1.7, and one at 1.4 - yet
I invariably have to stop down in order to get a nicely sharp image, which
sort of defeats the object of the 'fast glass', doesn't it?


Depends on what your needs are. If all you want is sharpness and lots
of depth of field, then no, there's not much need. If you shoot a lot
of landscapes with a tripod, you're probably not going to draw a lot of
benefit from a really fast lens.

If you're shooting moving subjects, like animals in nature or sporting
events, and/or shooting in poor lighting conditions, as with indoor
sporting events, you need all the light-collecting power you can get at
the highest shutter speed available. These conditions are also
instances where you'd often want less depth of field.

I mean, why pay three times the price for a 'fast' lens, when you only end
up stopping it down? I've got a theory that it's the mania for bright lenses
that's behind a lot of the 'focus fuss' that clogs up the various forums -
perhaps people don't realise that you're just not going to get the same
image quality out of wide open lens and are mistaking 'softness' for focus
issues. Just a thought.


That depends more on the lens design. A Canon L-series lens at f/2.8 is
going to probably be a lot sharper than my bottom-of-the-barrel 70-300
at ANY aperture.


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  #19  
Old January 9th 06, 06:15 AM posted to rec.photo.digital,rec.photo.digital.slr-systems
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Default fast glass?


"Danny" wrote in message
...
everyone seems to want 'fast glass' - f/2.8, 1.7, 1.4, etc, but I'm left
wondering 'why' As most people know, lenses are not at their sharpest

wide
open - usually requiring f/7 - 9 (ish) before they attain their maximum
potential.


My understanding is that most lenses are sharpest when stopped down 2 to 3
stops - therefore - if the lens is faster in the first place then you'll
still be shooting faster compared to a slower lens.

DOF can get too critical to use F2.8 in close-up work (assuming you're
trying to get all of the subject matter in focus) - but I regularly shoot
distant objects @ F2.8 (Fastest my lenses will go).

Last but not least, often only the faster lenses come with an IS option eg
the 70-200 F2.8L IS - the more petite F4 version is NON-IS only.



  #20  
Old January 9th 06, 06:20 AM posted to rec.photo.digital,rec.photo.digital.slr-systems
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Posts: n/a
Default fast glass?

Danny wrote:
"Charles" wrote in message
...

In article , Danny
wrote:


Why is their always a smart-arse on every Usenet group?


I meant what I said. Read some basic photography books and you will
understand why we need fast glass.




OK. let's try again, shall we?

I'm well aware why some people 'need' fast lenses, and those that do need
them usually buy high quality optics (at high quality prices) that are up to
the job.

My point (perhaps not clearly made) is that the great mass of 'hobby'
photographers are buying cheaper lenses that are unsharp at wide apertures,
simply because an f/2.8 badge on a lens gives it more street cred than an
f/5.6 - even though the cheap ".8 might very well have to be stopped down
past the 'slower' lens in order to get a decently sharp image.

I know - because I've been suckered by the manufacturers as well, and If I
was buying them again I'd be far less impressed by the alleged maximum
aperture, and concentrate on element quality and construction.


That's fine for YOUR needs. Not everyone has the same needs.

I do a lot of shooting in nightclubs. I could really do with something
faster than I've got (EF-S 18-55 that came with my 300D maxes out at
f/4). Even a cheap f/2 would make my life a lot happier; as it is, the
lighting in most venues is so limited, I simply can't shoot available
light: even at ISO 1600, f/4 requires a shutter speed of 1/15 or slower.
A super-sharp lens is quite meaningless if I've got tons of motion blur.


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