Does a good lens help focusing?

I have an Olympus E500 which is fairly good,
but I want better focusing - if possible.

Does a more expensive, or prime lens, give a
better sharp focus generally?

If so, what are the parameters I should look
for in such a lens?

pj

On 2008-03-31 19:20:09 -0400, "Peter Jason" said:

I have an Olympus E500 which is fairly good,
but I want better focusing - if possible.

Does a more expensive, or prime lens, give a
better sharp focus generally?

If so, what are the parameters I should look
for in such a lens?

pj

Yes. Hold all else equal, a faster (ie. Wider aperature) better
quality lens will improve both the ability of your eyes and the AF
system to focus quciker and faster. I stress all else being equal.
Take the SLR or DSLR of your choice and put on a variety of lenses.
Aperature has the largest effect. An F2.8 lens is easier to focuse
than and F4.5 lens. The better and faster lenses will focus more
quickly in a given light situaton. Now, you can not go comparing
cameras. On the manual side, view finder quality has a lot to do with
the your ability to focus. On AF systems the lens, the sensors, the
motors, the processor and the focusing algorithms all have an effect.
So, you can not say with an accuracy that a superb canon lens will
focuse faster than an equal focal length Nikon or vice versa, as the
cameras are different and introduce many factors. You need to pick a
couple of camera/lens combinations for what you want to do and try them.
--
jen ... not.. home...//// yahoo... com

Jim Nason wrote:
On 2008-03-31 19:20:09 -0400, "Peter Jason" said:

I have an Olympus E500 which is fairly good,
but I want better focusing - if possible.

Does a more expensive, or prime lens, give a
better sharp focus generally?

If so, what are the parameters I should look
for in such a lens?

pj

Yes. Hold all else equal, a faster (ie. Wider aperature) better quality
lens will improve both the ability of your eyes and the AF system to
focus quciker and faster. I stress all else being equal. Take the
SLR or DSLR of your choice and put on a variety of lenses. Aperature
has the largest effect. An F2.8 lens is easier to focuse than and F4.5
lens. The better and faster lenses will focus more quickly in a given
light situaton. Now, you can not go comparing cameras. On the manual
side, view finder quality has a lot to do with the your ability to
focus. On AF systems the lens, the sensors, the motors, the processor
and the focusing algorithms all have an effect. So, you can not say
with an accuracy that a superb canon lens will focuse faster than an
equal focal length Nikon or vice versa, as the cameras are different and
introduce many factors. You need to pick a couple of camera/lens
combinations for what you want to do and try them.


This is not entirely true. Unless the sensor is specially designed, the
way the focusing lenses on the AF module work will automatically make
all lenses appear to be a fixed aperture - typically f6.3. No matter how
much wider the lens is, the sensor can only 'see' f6.3 (rather like a
viewfinder with a clear screen). Special sensors which can see f2.8 are
added (example, my Sony A700 has one central sensor able to benefit from
f2.8 lenses, the rest effectively reduce all lenses to f6.3). The
Olympus E-500, I think, does not have any wide aperture sensors. I may
be wrong, the specs need to be looked up, but I'm pretty sure it uses
'standard' sensors which may be f5.6 effective aperture limitation on
the 4/3rds system.

David

--
Icon Publications Ltd, Maxwell Place, Maxwell Lane, Kelso TD5 7BB
Company Registered in England No 2122711. Registered Office 12 Exchange
St, Retford, Notts DN22 6BL
VAT Reg No GB458101463
Trading as Icon Publications Ltd, Photoworld Club and Troubadour.uk.com
www.iconpublications.com - www.troubadour.uk.com - www.f2photo.co.uk -
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Tel +44 1573 226032

All other things being equal, a lens with a maximum aperture of f1.4 will allow the autofocus to focus faster (and maybe more
precisely) than a lens with a maximum aperture of, say, f4 or less. That doesn't mean the pictures will be any sharper though. In
fact, 'fast' lenses tend to be less sharp overall than 'slow' lenses of the same kind (ie prime or zoom), even when both are stopped
down to the same aperture.

One thing not to overlook if you're after better viewfinder clarity is making sure that the viewfinder diopter adjuster (if your
camera has one) is correctly set for *your* eyes. That alone can make vastly more difference than changing lenses.

Cheers
--
cmyk
"Peter Jason" wrote in message ...
I have an Olympus E500 which is fairly good, but I want better focusing - if possible.

Does a more expensive, or prime lens, give a better sharp focus generally?

If so, what are the parameters I should look for in such a lens?

pj

David Kilpatrick wrote:

the way the focusing lenses on the AF module work will automatically
make all lenses appear to be a fixed aperture - typically f6.3. No matter
how much wider the lens is, the sensor can only 'see' f6.3 (rather like a
viewfinder with a clear screen).

I never heard of that, thanks. Here's a similar scenario:

David Ruether talked about the viewfinder system's limitations. As I
understand the viewfinder's ground glass allows some direct transmission
to your eye (aerial image) and some of the image is captured on the
ground glass freezing the aperture as the sensor will see it given it's
size.

What the eye sees directly is different though because the eye is a
small sensor camera with much more depth of field, more like a pocket
sized point & shoot camera.

The part that gets locked into the ground glass shows translucently
through the sharp eye image so you really have two apertures overlaid
but it ends up looking more like about f/2.8 so for practical purposes.

Theoretically an f/1.2 lens is no easier to focus than an f/2.8 lens
manually although perhaps the partial ground glass image helps somewhat.
I had thought maybe the dimensions of the mirror box limit apparent
aperture in the viewfinder but the explanation of the translucent
overlay makes more sense.


Special sensors which can see f2.8 are
added (example, my Sony A700 has one central sensor able to benefit from
f2.8 lenses, the rest effectively reduce all lenses to f6.3). The
Olympus E-500, I think, does not have any wide aperture sensors. I may
be wrong, the specs need to be looked up, but I'm pretty sure it uses
'standard' sensors which may be f5.6 effective aperture limitation on
the 4/3rds system.

David

"Peter Jason" wrote in message
...
I have an Olympus E500 which is fairly good, but I want better focusing -
if possible.

Does a more expensive, or prime lens, give a better sharp focus generally?

If so, what are the parameters I should look for in such a lens?

http://www.cambridgeincolour.com/tut...-autofocus.htm

Paul Furman wrote:
David Kilpatrick wrote:

the way the focusing lenses on the AF module work will automatically
make all lenses appear to be a fixed aperture - typically f6.3. No
matter how much wider the lens is, the sensor can only 'see' f6.3
(rather like a viewfinder with a clear screen).

I never heard of that, thanks. Here's a similar scenario:

David Ruether talked about the viewfinder system's limitations. As I
understand the viewfinder's ground glass allows some direct transmission
to your eye (aerial image) and some of the image is captured on the
ground glass freezing the aperture as the sensor will see it given it's
size.


I did a visual explanation of this using the Canon f1.2 85mm and
compared an actual shot through the viewfinder, with live view:

http://www.dphotoexpert.com/2007/09/...lr-viewfinder/

It shows exactly how much the translucency factor of the focusing screen
affects apparent depth of field.

The terminology used by makers for AF modules is confusing - they refer
to special sensors which will work at 'f2.8 or greater'. Of course all
the sensors work at f2.8 or greater, they just don't show any benefit.
The special wide aperture sensors benefit from the wider aperture.

David

--
Icon Publications Ltd, Maxwell Place, Maxwell Lane, Kelso TD5 7BB
Company Registered in England No 2122711. Registered Office 12 Exchange
St, Retford, Notts DN22 6BL
VAT Reg No GB458101463
Trading as Icon Publications Ltd, Photoworld Club and Troubadour.uk.com
www.iconpublications.com - www.troubadour.uk.com - www.f2photo.co.uk -
www.photoclubalpha.com - www.minoltaclub.co.uk
Tel +44 1573 226032

Thank you for all replies.

Peter