DSLR vs. P&S Smackdown -- the Answer

David J Taylor wrote:
SMS wrote:
David J Taylor wrote:

Yes, I had a similar front-of-lens converter (TC-E2) for my Nikon
900, and the specifications had a similar statement about the
f/number, which I am happy to accept. In reality, the converter's
bulk, and the inconvenience of use meant that it was left at home
more often than not.
It also blocked the optical viewfinder, it blocked the internal flash,
andit blocked the flash sensor. Since it was only usable at focal
lengths longer than 60mm, you had to take it on and off a lot.

Yes.

I was always amused at what one guy did with his 950/990 and TC-E2:

"http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/Odd-Stuff/Reversed-Nikkor/reverse-closeup.html"

Fascinating! Thanks.

I used to hold an old projector lens to the front of my Oly C3030 (circa
2000) with pretty amazing results for macro. These days macro and
astronomy folks use DSLRs for best results.

--
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam

nospam wrote:
In article , David J
Taylor
wrote:

Since it was only usable at focal
lengths longer than 60mm, you had to take it on and off a lot.

kind of like swapping lenses on a dslr...

No, as it was screw mount compared to bayonet on a DSLR. Much
/worse/ than swapping DSLR lenses!

true, it reminded me of using old pentax cameras.

however, my point is that a dslr user with kit lenses that don't have
a lot of overlap, such as an 18-70 and 70-300, will be swapping a lot
too.

Yes, if you aren't using the 18-200mm, then something like 18-100mm and
35-200mm would mean less swapping, although it might be more expensive and
not provide quite a good optical performance. Of course, as DSLR bodies
are no longer /that/ expensive, a second body for the second lens is what
some might consider...

Cheers,
David

Scott W writes:
On Aug 9, 11:13*pm, Gisle Hannemyr wrote:

Unfortunately, it doesn't work that way. *Your converter lenses can be
humongous, but the speed of your combo will still be the true focal
length divided by diameter of the camera's aperture. *If the
"mystery camera" is the Canon Powershot S2 IS, this works out as:

* * * *208.08 mm / 20.57 mm = f/10. *


A much as it pains me, and believe me is does, I think in this case
Vern might be correct. If the primary lens is f/3.5, as long as the
converters in front of it don’t limit the light falling on its
aperture, then the system remains an f/3.5 system.

I believe Scott is right. Gisle's reasoning isn't that far off, but the
flaw is that the "aperture" of the lens is actually the diameter of its
entrance pupil. When you stack an afocal converter on the *front* of a
lens, it magnifies the diameter of the entrance pupil of the "main"
lens, so the entrance pupil of the combination of all the glass can be
substantially larger than that of the main lens alone. (It can't be
larger than the diameter of the front element of the converter, but
that's often quite a bit larger than the front element of the main lens.

So yes, in the best case, the f/number of the lens remains the same but
the aperture gets larger when you add a converter to the front.

On the other hand, a teleconverter added to the *rear* of a SLR lens
does indeed change the f/number, because the entrance pupil does not
change size but the effective focal length does.

Though both of these "converters" increase magnification, they operate in
completely different ways.

Dave

Dave Martindale wrote:
Scott W writes:
On Aug 9, 11:13 pm, Gisle Hannemyr wrote:

Unfortunately, it doesn't work that way. Your converter lenses can be
humongous, but the speed of your combo will still be the true focal
length divided by diameter of the camera's aperture. If the
"mystery camera" is the Canon Powershot S2 IS, this works out as:

208.08 mm / 20.57 mm = f/10.


A much as it pains me, and believe me is does, I think in this case
Vern might be correct. If the primary lens is f/3.5, as long as the
converters in front of it don’t limit the light falling on its
aperture, then the system remains an f/3.5 system.

I believe Scott is right. Gisle's reasoning isn't that far off, but the
flaw is that the "aperture" of the lens is actually the diameter of its
entrance pupil. When you stack an afocal converter on the *front* of a
lens, it magnifies the diameter of the entrance pupil of the "main"
lens, so the entrance pupil of the combination of all the glass can be
substantially larger than that of the main lens alone. (It can't be
larger than the diameter of the front element of the converter, but
that's often quite a bit larger than the front element of the main lens.

So yes, in the best case, the f/number of the lens remains the same but
the aperture gets larger when you add a converter to the front.

On the other hand, a teleconverter added to the *rear* of a SLR lens
does indeed change the f/number, because the entrance pupil does not
change size but the effective focal length does.

Though both of these "converters" increase magnification, they operate in
completely different ways.

If front mount teleconverters worked well they would probably be more
common for 35mm lenses where people spend 100's of thousands of dollars
on specialty telephoto lenses but I've never heard of one instance of
such a device.

In any case it is a simple matter to test the transmission by taking a
photo & measuring the exposure time, compared with the converter on &
off, pointing at a white wall.

--
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam

-hh wrote:
SMS wrote:
In any case the bottom line is that Vern is trying to promote a kludge
of conversion lenses on a P&S as an alternative to a D-SLR, without
understanding critical factors such as f/stop, aperture, focal length,
vignetting, and chromatic aberration. He apparently believes that if
it's physically possible to attach something to a point and shoot that
by default it must work perfectly.

Well to be fair, he really isn't trying to promote anything. He made up
a story about a 1249mm focal length at f/3.5, and several of us were
lured into responding even though he clearly has no experience with
either P&S or D-SLR cameras, and has no understanding of photography.
Somewhere along the line the 1249mm morphed into 1359mm!

Here's another fairy tale, but on the dSLR side, as part of the
ongoing hunt for clues on the Canon 5D replacement:

http://www.upcdatabase.com/item/0002513465529

Yup, an EF 10-2000mm L glass ... 7 ounces! Whoo Hoo!
And apparently, its going to have a street price under $300 too :-)

I just found a great retailer on the 'Net who's guaranteed me delivery
on the first two hundred, and I had to deposit only $ 100 per lens! I
can't wait!!!!! OMG!!!!!!

Any one who wants one, send me $295 and I will forward soon as I get 'em!!!!
--
john mcwilliams

-hh wrote:
John McWilliams wrote:
Any one who wants one, send me $295 and I will forward soon as I get 'em!!!!

Got it right here, in cash; I'll send it right out to you...what's
your fax#? :-)

I don't do fax; that's soooo 20th C. However, you bank account, two
credit card numbers + codes, D/L, will secure two, now, TWO! for the
price of one!

PS DON'T post these numbers here as someone else might see them!! This
is a WARNING!

Your a great E-BAYER!!! A Plus and higher! Pays on time! (Just warming
up; grammar going to piece's, too.)

:-)

--
john mcwiliams

John wrote on Fri, 15 Aug 2008 17:26:38 -0700:

-hh wrote:
John McWilliams wrote:
Any one who wants one, send me $295 and I will forward soon as I get
'em!!!!

Got it right here, in cash; I'll send it right out to
you...what's your fax#? :-)

I don't do fax; that's soooo 20th C.

How do you handle requests for insurance estimates, medical tests etc.?
Do you drive over and hand deliver? I don't actually have a FAX machine
but use my scanner and computer.



--

James Silverton
Potomac, Maryland

Email, with obvious alterations: not.jim.silverton.at.verizon.not

James Silverton wrote:
John wrote on Fri, 15 Aug 2008 17:26:38 -0700:

-hh wrote:
John McWilliams wrote:
Any one who wants one, send me $295 and I will forward soon as I get
'em!!!!

Got it right here, in cash; I'll send it right out to
you...what's your fax#? :-)

I don't do fax; that's soooo 20th C.

How do you handle requests for insurance estimates, medical tests etc.?
Do you drive over and hand deliver? I don't actually have a FAX machine
but use my scanner and computer.

The latter. I rather loathe faxes altogether as it's such a wasteful
technology, but some outfits just seem to demand them as 'proof'.

--
john mcwilliams

-hh wrote on Mon, 18 Aug 2008 04:21:56 -0700 (PDT):

John McWilliams wrote:
James Silverton wrote:

How do you handle requests for insurance estimates, medical
tests etc.? Do you drive over and hand deliver? I don't
actually have a FAX machine but use my scanner and
computer.

The latter. I rather loathe faxes altogether as it's such a
wasteful technology, but some outfits just seem to demand
them as 'proof'.

Scan -- PDF -- email works well, and generally, anyone who
doesn't accept that today is a business you need to document
your interactions with very carefully.

In Windows, the same route but with the FAX wizard designated as a
printer keeps the conservatives happy.

--

James Silverton
Potomac, Maryland

Email, with obvious alterations: not.jim.silverton.at.verizon.not

Scott wrote on Mon, 18 Aug 2008 09:05:31 -0700 (PDT):

Scan -- PDF -- email works well, and generally, anyone who
doesn't accept that today is a business you need to document
your interactions with very carefully.

For sending copies of documents that works well as a
replacement for a fax, and I have yet to have a company
complain about it. For receiving we still have a few people
that we have to deal with that insist on sending faxes, so we
keep a fax machine around for them.

You can receive a FAX with Windows and its "wizard". Of course, you need
a phone connection but those are cheap. There are "services" that will
let you send and receive faxes over broadband but I've never found any
necessity to pay for them.

--

James Silverton
Potomac, Maryland

Email, with obvious alterations: not.jim.silverton.at.verizon.not