Olympus OM enthusiasts' digital prayers have been answered ...

"Bruce" wrote in message
...
Many, if not most OM Zuiko lenses present significant problems when
used on a (Micro) Four Thirds digital sensor. The sensor design
strongly prefers telecentric lenses, where most of the light rays are
approximately perpendicular to the sensor when they hit.

Right, so just who's "prayers" are being answered simply by a retro "OM"
look I wonder? The "look" was hardly what attracted most people to the OM
system, it was the size weight and performance for me.


The result is that many OM lenses are poor performers on digital
sensors, particularly on the small (Micro) Four Thirds sensor. They
suffer particularly from vignetting and their overall performance is
degraded compared to their performance on film.

Haven't used one on 4/3, but I'm puzzled how they suffer from any
significant vignetting when your only using the middle half of the lens
circle?


Olympus helpfully released a list of OM lenses with indications as to
which would performed well, or less well, with suggested limitations
on some in terms of lens apertures. I was so put off by the
complexity of this list, and the dire warnings it contained,

Do you have a link for that list? Sounds interesting.


that I
never even tried an OM Zuiko lens on my E-1 bodies. There was no need
because I no longer owned any OM gear and the Zuiko Digital lenses
were in any case superb.

True, I would only use an OM lens because I already had it and did not want
to buy another lens of that type. Which also rules out buying another camera
body just to use the old lenses I guess! So looks like my "OM enthisiasts
prayers" are never going to be answered :-(



So the OM-D E-M5 is not intended as a digital body for use with OM
lenses. It is more about retro styling that taps into the positive
sentiment for the OM system that is still around. People will buy it
because it looks like an OM SLR, not because it accepts OM lenses.

Right, hardly anybody "praying" for that AFAIK. Which is NOT to say it won't
be a good camera for some, or that nobody will buy it of course.

Trevor.

"Bruce" wrote in message
...
Haven't used one on 4/3, but I'm puzzled how they suffer from any
significant vignetting when your only using the middle half of the lens
circle?


I explained it in my previous post. You replied to that post but
snipped the relevant paragraph. ;-)

No, you explained why it would happen if you were using the full lens image
circle, but since your not, I can't see how it's a big problem? Sure there
might be a slightly measurable loss, but a visable vignette, really? Not
saying your wrong, but I'd love to know the TRUE extent.

Trevor.

"Bruce" wrote in message
...
Mort wrote:

I still have about a dozen OM lenses for my two OM-4T bodies. It
certainly would be nice to have a new Olympus digital body with the OM
lens mount and auto diaphragm, and I would not mind manual focus. I
suppose that it is just daydreaming.


Unfortunately yes, that is just daydreaming. Olympus rejected the
idea of a digital OM because of the incompatibility of many OM lenses
with digital sensors, which I explained in the post you replied to.


Well it's all relative. I note they don't recommend the 75-150 below 100mm
and 5.6, yet it works well enough on a Canon DSLR, on par with the kit zooms
at least, which are only f5.6 at that range anyway. And most of the other OM
lenses I have seem to be reasonably OK on their list.

Have you actually tried any OM lenses on a E-series camera yourself? I think
Olympus is just advising caution. And of course they'd prefer to sell more
new lenses :-)
But as I said, buying a fairly expensive DSLR body just to use some old
sub-optimal lenses is probably not such a great idea anyway. And simply
using a retro look as a marketing feature will appeal to some, but there are
more important things I look for in a camera.

Trevor.

"Bruce" wrote in message
...
Haven't used one on 4/3, but I'm puzzled how they suffer from any
significant vignetting when your only using the middle half of the lens
circle?


I explained it in my previous post. You replied to that post but
snipped the relevant paragraph. ;-)

No, you explained why it would happen if you were using the full lens
image
circle, but since your not, I can't see how it's a big problem?


You obviously didn't read what I wrote. Your loss. ;-)

Nope I read it, and it doesn't match my experience, so I queried what YOUR
experience was? (rather than theory)
Maybe it's only a major problem with Olympus 4/3 sensors perhaps, but as I
said, it's all relative.

Trevor.

In article , Bruce
writes

If there wasn't a problem, as you so confidently assert, why on earth
would Olympus have gone to such lengths?

To justify making small 4-turds sensors in the first place!
That's when they came out with the "telecentric is best for digital"
myth in the first place and it was shortly proven to be wrong by
measurement. The light fall-off due to non-telecentricity is *LESS* on
Olympus (and Canon FF sensors for that matter) than it was on film!

OM lenses work just as well on digital as they did on film, which
doesn't mean telecentric lenses can't work better, but the argument was
false to begin with and was merely an attempt by Olympus to justify
their investment in cheap chips.

Try the counter argument: if there was a problem, why are the 4-turds
consortium the only folk that have it? Whilst Leica do take steps to
reduce the issue on their sensor, neither Canon, Nikon nor Sony do.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

In article , Bruce
writes
Mort wrote:

I still have about a dozen OM lenses for my two OM-4T bodies. It
certainly would be nice to have a new Olympus digital body with the OM
lens mount and auto diaphragm, and I would not mind manual focus. I
suppose that it is just daydreaming.


Unfortunately yes, that is just daydreaming. Olympus rejected the
idea of a digital OM because of the incompatibility of many OM lenses
with digital sensors, which I explained in the post you replied to.

Which is just nonsense - I have several OM lenses that work just as
well, perhaps even better, on my Canon FF sensors as they did on film in
an OM body.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

In article , Bruce
writes

Many, if not most OM Zuiko lenses present significant problems when
used on a (Micro) Four Thirds digital sensor. The sensor design
strongly prefers telecentric lenses, where most of the light rays are
approximately perpendicular to the sensor when they hit.

That statement is simple repetition of Olympus's original false
justification for making the 4-turds sensor smaller than FF in the first
place, and that was disproved when FF sensors were demonstrated to work
perfectly well with OM lenses. There is NOTHING in the Olympus sensor
design which "strongly prefers telecentric lenses" and several 4-turds
lenses are just as non-telecentric as their equivalent OM lenses were.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

On 2012-02-07 13:12:37 +0000, Kennedy McEwen said:

In article , Bruce
writes

If there wasn't a problem, as you so confidently assert, why on earth
would Olympus have gone to such lengths?

To justify making small 4-turds sensors in the first place!
That's when they came out with the "telecentric is best for digital"
myth in the first place and it was shortly proven to be wrong by
measurement. The light fall-off due to non-telecentricity is *LESS* on
Olympus (and Canon FF sensors for that matter) than it was on film!

Illumination falloff for a non-telecentric lens is approximately a
cosine to the fourth power. The only way a digital sensor can suffer
_less_ falloff than film is by altering the angle of the non-central
micro-lenses. In all other cases, a digitital sensor will suffer more
light falloff than film.


OM lenses work just as well on digital as they did on film, which
doesn't mean telecentric lenses can't work better, but the argument was
false to begin with and was merely an attempt by Olympus to justify
their investment in cheap chips.

Try the counter argument: if there was a problem, why are the 4-turds
consortium the only folk that have it? Whilst Leica do take steps to
reduce the issue on their sensor, neither Canon, Nikon nor Sony do.

"Bruce" wrote in message
...
Not only don't you understand what I wrote, but you seem wilfully
determined not to understand.

DITTO!


If there wasn't a problem, as you so confidently assert,

I only suggested it didn't match my experience and you have now explained
why. Thank you!


Your Head In The Sand Club membership card is in the mail. ;-)

Your unnecessarily antagonistic club membership card is in the mail, no
wait, not worth the postage. :-)

Trevor.

In article 2012020714103581999-pete3attkins@nospamntlworldcom, Pete A
writes
On 2012-02-07 13:12:37 +0000, Kennedy McEwen said:

In article , Bruce
writes
If there wasn't a problem, as you so confidently assert, why on
earth
would Olympus have gone to such lengths?

To justify making small 4-turds sensors in the first place!
That's when they came out with the "telecentric is best for digital"
myth in the first place and it was shortly proven to be wrong by
measurement. The light fall-off due to non-telecentricity is *LESS*
on Olympus (and Canon FF sensors for that matter) than it was on film!

Illumination falloff for a non-telecentric lens is approximately a
cosine to the fourth power. The only way a digital sensor can suffer
_less_ falloff than film is by altering the angle of the non-central
micro-lenses.

Wrong.

3D microlens v's 2D flat film surface. A tennis ball has the same cross
section no matter what angle you view it from, while a flat sheet of
film has a cross section that is cos^2. Any 3D view of the microlens
means less than cos^4 fall-off. Also, if the "image" from the
micro-lens is smaller than the sensitive area of the pixel, the
illumination fall-off on a digital sensor will *always* be less than
film - by 2 of those four cosines!

Try measuring it, its not that difficult but too many folk would prefer
to regurgitate the dogma than find out the truth for themselves!
Alternatively, google my measurements from 5 or 6 years ago where this
was discussed to death - the Olympus dogma death!

The Olympus "telecentric" argument was just an excuse for selling tiny
cheap chips. Nothing wrong with that - there is a huge market for
cheaper cameras - but they lost all credibility by trying to justify an
economic argument with fake science.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)