50 mm tele prime, has anyone tried?

I'm different. I have the opinion a "usable" picture has 1-2 MP
resolution, I'd say "sufficient" resolution is 3-4 MP. I'd classify 10
MP as "mostly non-achievable".

I'm trying to decide what would be the next step after replacing the
ridiculous Canon kit-lens with a decent 2.8 from Sigma or Tamron. I'd
really would like to go wide angle, but that will be expensive and
heavy, so lets look at the tele side for a moment instead. Something
like 25-100 would provide a nice overlap, I frequently just want to
bring one lens, but it would have mass, bulk and cost money. As said,
I'm not really all that interested in tele. Besides, tele without image
stabilization seems almost unusable. So, I got this idea:

Buy a Canon 50/1.8 for almost no money and use it as a tele by cropping
the 10 MP high quality picture it delivers. This will (surprisingly)
give all these benefits:

* Worlds cheapest tele lens $100 - On pair with my tele interest.
* Worlds most lightweight tele 130 g - Perhaps it won't stay at home?
* Has image stabilization - F/2 versus F/4 or F/5.6 for the real thing.

Great when you think about it, right? Now, my question is: Will this
work? Is a 50 mm prime so god, that a 2 MP crop actually has resolution
close to 2 MP? Will a resampled (2 MP) full-frame image from a real
tele be significantly sharper, or only slightly better? Can handheld
(w/o IS) at F/4 really compete with a F/2 50 mm crop with respect to
camera-shake?
/Bengt

On Jul 13, 3:27 pm, "Bengt C" wrote:
I'm different. I have the opinion a "usable" picture has 1-2 MP
resolution, I'd say "sufficient" resolution is 3-4 MP. I'd classify 10
MP as "mostly non-achievable".

I'm trying to decide what would be the next step after replacing the
ridiculous Canon kit-lens with a decent 2.8 from Sigma or Tamron. I'd
really would like to go wide angle, but that will be expensive and
heavy, so lets look at the tele side for a moment instead. Something
like 25-100 would provide a nice overlap, I frequently just want to
bring one lens, but it would have mass, bulk and cost money. As said,
I'm not really all that interested in tele. Besides, tele without image
stabilization seems almost unusable. So, I got this idea:

Buy a Canon 50/1.8 for almost no money and use it as a tele by cropping
the 10 MP high quality picture it delivers. This will (surprisingly)
give all these benefits:

* Worlds cheapest tele lens $100 - On pair with my tele interest.
* Worlds most lightweight tele 130 g - Perhaps it won't stay at home?
* Has image stabilization - F/2 versus F/4 or F/5.6 for the real thing.

Great when you think about it, right? Now, my question is: Will this
work? Is a 50 mm prime so god, that a 2 MP crop actually has resolution
close to 2 MP? Will a resampled (2 MP) full-frame image from a real
tele be significantly sharper, or only slightly better? Can handheld
(w/o IS) at F/4 really compete with a F/2 50 mm crop with respect to
camera-shake?
/Bengt

Keep dreaming. A 100mm or 200mm lens has to be pretty bad to have its
image beaten by a hugely cropped one from a 50mm. Also, you use a
Canon so how dark is the subject you intend shooting, if you can't use
a 100-200mm lens and get a steady shot?
Also, Canon is not know for superb wide and medium primes, unless you
can afford the 50mm f1.2.

Bengt C wrote:
I'm different. I have the opinion a "usable" picture has 1-2 MP
resolution, I'd say "sufficient" resolution is 3-4 MP. I'd classify 10
MP as "mostly non-achievable".

I'm trying to decide what would be the next step after replacing the
ridiculous Canon kit-lens with a decent 2.8 from Sigma or Tamron. I'd
really would like to go wide angle, but that will be expensive and
heavy, so lets look at the tele side for a moment instead. Something
like 25-100 would provide a nice overlap, I frequently just want to
bring one lens, but it would have mass, bulk and cost money. As said,
I'm not really all that interested in tele. Besides, tele without
image stabilization seems almost unusable. So, I got this idea:
[]
/Bengt

Simpler to replace camera body and lens with a Nikon body, and their 18 -
200mm image stabilised lens.

G

David

"Bengt C" schreef in bericht
newsp.tve4cao09uyazu@thinkpad...
I'm different. I have the opinion a "usable" picture has 1-2 MP
resolution, I'd say "sufficient" resolution is 3-4 MP. I'd classify 10
MP as "mostly non-achievable".


If you consider a 1-2 MP picture "usable", realise that a 1-2 MP
picture has 1-2 M pixels with each three colors. If this picture is
made with a 10 MP camera, these 1-2 MP pixels contain real
information.

Making the picture with a 1-2 MP camera gives you only
1-2 M pixels with one color each, this is less information than
a 1-2 Mp picture but reduced from a 'larger' format.

a 50 mm lens will give you a 2 time fold zoom, but only with
a quarter (1/4) of the pixels used. So 10 MP off one color
pixels gets reduced to 2.5 MP off one colore pixels.

a 50 mm lens will give you a 4 time fold zoom, but only with
a sixteenth (1/16) of the pixels used. So the 10 Mp off one color
pixes gets reduced to 0.625 one color pixels.

So allthough you sceme is feasable, your quality will suffer
even with moderate (digital) zoom.

Digital zoom or cropping is a very valuable tool, but the
range it can be used for is limited. A factor of 2 liniear is
about the max in most situations.
(Starting of with 6 MP crop of 2 times liniear leaves 1.5
MP which is about the amount of most displays and still
usable for a 4 inch x 6 inch print)

ben


I'm trying to decide what would be the next step after replacing the
ridiculous Canon kit-lens with a decent 2.8 from Sigma or Tamron. I'd
really would like to go wide angle, but that will be expensive and
heavy, so lets look at the tele side for a moment instead. Something
like 25-100 would provide a nice overlap, I frequently just want to
bring one lens, but it would have mass, bulk and cost money. As said,
I'm not really all that interested in tele. Besides, tele without image
stabilization seems almost unusable. So, I got this idea:

Buy a Canon 50/1.8 for almost no money and use it as a tele by cropping
the 10 MP high quality picture it delivers. This will (surprisingly)
give all these benefits:

* Worlds cheapest tele lens $100 - On pair with my tele interest.
* Worlds most lightweight tele 130 g - Perhaps it won't stay at home?
* Has image stabilization - F/2 versus F/4 or F/5.6 for the real thing.

Great when you think about it, right? Now, my question is: Will this
work? Is a 50 mm prime so god, that a 2 MP crop actually has resolution
close to 2 MP? Will a resampled (2 MP) full-frame image from a real
tele be significantly sharper, or only slightly better? Can handheld
(w/o IS) at F/4 really compete with a F/2 50 mm crop with respect to
camera-shake?
/Bengt

Bengt C wrote:
I'm different. I have the opinion

Everybods's entitled to one.

a "usable" picture has 1-2 MP
resolution, I'd say "sufficient" resolution is 3-4 MP. I'd classify 10
MP as "mostly non-achievable".

May I introduce you to medium format digibacks?

I'm trying to decide what would be the next step after replacing the
ridiculous Canon kit-lens with a decent 2.8 from Sigma or Tamron.

That will depend on what lens you replace it with, what you
want, your budget, and so on and so on.

I'd really would like to go wide angle, but that will be expensive and
heavy,

Depends on your definition of heavy and expensive. Comparing
the 17-40mm f/4 to the 70-200mm f/2.8 IS, I know which one of
these is heavy and expensive, and it ain't the 17-40.

so lets look at the tele side for a moment instead. Something
like 25-100 would provide a nice overlap,

Since you talk Canon, a 25mm lens has the same view angle as
a 40mm lens --- not enough wide angle. The 17-40mm is
probably a better match for you, especially if you don't mind
cropping.

I frequently just want to
bring one lens, but it would have mass, bulk and cost money.

Well, a lens without mass, bulk and costing money doesn't exist,
at least not till anti-gravity lifters, inertia compensators and
infinite wealth for everyone are available.

However, there are bigger and smaller, lighter and heavier,
expensive and cheap lenses.

As said,
I'm not really all that interested in tele. Besides, tele without image
stabilization seems almost unusable.

How did people do it 10 years ago, then?
Ever heard of monopods, tripods, beanbags, bracing, fast exposure
times and so on?

So, I got this idea:

Buy a Canon 50/1.8 for almost no money and use it as a tele by cropping
the 10 MP high quality picture it delivers. This will (surprisingly)
give all these benefits:

* Worlds cheapest tele lens $100 - On pair with my tele interest.

Tamron's 55-200 is in the same price class and needs less
cropping.

* Worlds most lightweight tele 130 g - Perhaps it won't stay at home?

If your problem is weight, use a compact camera, DSLRs ain't
for you.

* Has image stabilization - F/2 versus F/4 or F/5.6 for the real thing.

I still prefer a 70-200 f/2.8 with IS. Sorry.

Great when you think about it, right?

More like "run off this roof, flapping your wings and you'll fly"
--- sounds great, but only in theory.

Now, my question is: Will this work?

Oh, you can crop as much as you like. I doubt you'll like the
results, but I don't know your standards.

Is a 50 mm prime so god, that a 2 MP crop actually has resolution
close to 2 MP?

That depends a lot on the prime, doesn't it? And on aperture
(you probably want f/5.6 --- here goes your image stabilisation).
And on de-bayering. And so on and so on.

Will a resampled (2 MP) full-frame image from a real
tele be significantly sharper, or only slightly better?

In general, yes, a *lot*, unless you use a coke bottle bottom
as lens.

Can handheld (w/o IS) at F/4 really compete with a F/2 50 mm crop with
respect to camera-shake?

If you crop the f/2 50mm shot to the same view angle as the
tele, and downsize the tele to your 2MPix, camera shake will be
identically good or bad for both, but the tele image will have
all information and less noise in the bargain.
You gain 2 stops, but on the tele you can up the ISO 2 stops and
still get no worse noise in the end result, so yes.

Once you throw in a tripod, mirror up condition and a remote
release, the 50mm is soundly beaten.


You miss a few crucial facts.
Let us assume you have a 1736 x 1160 pixels image (2 MPix).
On your 50mm crop it'll be built out of 868x580 green and 434x290
red and 434x290 blue measurements.

On a tele it'll be composed out of ca. 3888 x 2592 measurements,
1944 x 1296 green and 972 x 648 red and 972 x 648 blue
measurements.

You can do the math yourself, whether 868 measurements stretched to
1736 points is gonna give a sharper image than 1944 measurements
condensed to 1736 points. Yes, there are algorithms that can
get a lot out of the bayerized data, but they can do that in
both cases --- even though the tele + downsize probably won't
profit just as much as the straight crop --- it'll not make up
the differences all that much.

-Wolfgang

On Sat, 14 Jul 2007 18:44:12 +0200, Wolfgang Weisselberg
wrote:

Bengt C wrote:
[]
Buy a Canon 50/1.8 for almost no money and use it as a tele by cropping
the 10 MP high quality picture it delivers. This will (surprisingly)
give all these benefits:

* Worlds cheapest tele lens $100 - On pair with my tele interest.

Tamron's 55-200 is in the same price class and needs less
cropping.

Correct. But a F/2 50 mm prime can do other thing better. Things that I'll
do more often than shooting at say 135 mm focal length.


[]

Is a 50 mm prime so god, that a 2 MP crop actually has resolution
close to 2 MP?

That depends a lot on the prime, doesn't it? And on aperture
(you probably want f/5.6 --- here goes your image stabilisation).
And on de-bayering. And so on and so on.

Will a resampled (2 MP) full-frame image from a real
tele be significantly sharper, or only slightly better?

In general, yes, a *lot*, unless you use a coke bottle bottom
as lens.

Can handheld (w/o IS) at F/4 really compete with a F/2 50 mm crop with
respect to camera-shake?

If you crop the f/2 50mm shot to the same view angle as the
tele, and downsize the tele to your 2MPix, camera shake will be
identically good or bad for both, ...

How can that be so? A (budget) tele will only provide say F/4 at best.
I.e. in a situation where the prime will shoot at 1/250 s the tele will
shoot at 1/60 s or even slower.

...but the tele image will have all information and less noise in the
bargain. You gain 2 stops, but on the tele you can up the ISO 2 stops
and still get no worse noise in the end result, so yes.

Are you sure a 1600 ASA tele does outperform a 50 mm crop at 400 ASA?
You may be right regarding normal dSLR's, but it certainly isn't self-
evident on an Olympus (which I don't use for exactly that reason).


Once you throw in a tripod, mirror up condition and a remote
release, the 50mm is soundly beaten.

Of course. But, as I said before, weight (and bulk) matters and the
50 mm prime beats the tripod by an order of magnitude here. I can't
carry (nor fiddle with) a tripod at those not so frequent occations
when I want to take a tele shoot.


You miss a few crucial facts.

You miss my inital point which is...

Let us assume you have a 1736 x 1160 pixels image (2 MPix).
On your 50mm crop it'll be built out of 868x580 green and 434x290
red and 434x290 blue measurements.

On a tele it'll be composed out of ca. 3888 x 2592 measurements,
1944 x 1296 green and 972 x 648 red and 972 x 648 blue
measurements.

You can do the math yourself, whether 868 measurements stretched to
1736 points is gonna give a sharper image than 1944 measurements
condensed to 1736 points. Yes, there are algorithms that can
get a lot out of the bayerized data, but they can do that in
both cases --- even though the tele + downsize probably won't
profit just as much as the straight crop --- it'll not make up
the differences all that much.

....I consider a 1-2 MP picture "usable" and 3-4 MP "sufficient". My
first digicam, a 1.3 MP Canon A50, took lovely pics, but only under
certain (rare) conditions. I wonder whether 2 MP crops from my current
XTi with a F/2 prime will produce images comparable (better?) to that
camera. The XTi has, for instance, much better dynamic range.

/Bengt

"Bengt C" wrote in message newsp.tve4cao09uyazu@thinkpad...
I'm different. I have the opinion a "usable" picture has 1-2 MP
resolution, I'd say "sufficient" resolution is 3-4 MP. I'd classify 10
MP as "mostly non-achievable".

I'm trying to decide what would be the next step after replacing the
ridiculous Canon kit-lens with a decent 2.8 from Sigma or Tamron. I'd
really would like to go wide angle, but that will be expensive and
heavy, so lets look at the tele side for a moment instead. Something
like 25-100 would provide a nice overlap, I frequently just want to
bring one lens, but it would have mass, bulk and cost money. As said,
I'm not really all that interested in tele. Besides, tele without image
stabilization seems almost unusable. So, I got this idea:

Buy a Canon 50/1.8 for almost no money and use it as a tele by cropping
the 10 MP high quality picture it delivers. This will (surprisingly)
give all these benefits:

* Worlds cheapest tele lens $100 - On pair with my tele interest.
* Worlds most lightweight tele 130 g - Perhaps it won't stay at home?
* Has image stabilization - F/2 versus F/4 or F/5.6 for the real thing.

Great when you think about it, right? Now, my question is: Will this
work? Is a 50 mm prime so god, that a 2 MP crop actually has resolution
close to 2 MP? Will a resampled (2 MP) full-frame image from a real
tele be significantly sharper, or only slightly better? Can handheld
(w/o IS) at F/4 really compete with a F/2 50 mm crop with respect to
camera-shake?
/Bengt

Think about perspective rather than angle of view. Perspective and focal
length go hand in hand.

On Sun, 15 Jul 2007 02:20:46 +0200, N wrote:


"Bengt C" wrote in message
newsp.tve4cao09uyazu@thinkpad...
I'm different. I have the opinion a "usable" picture has 1-2 MP
resolution, I'd say "sufficient" resolution is 3-4 MP. I'd classify 10
MP as "mostly non-achievable".

I'm trying to decide what would be the next step after replacing the
ridiculous Canon kit-lens with a decent 2.8 from Sigma or Tamron. I'd
really would like to go wide angle, but that will be expensive and
heavy, so lets look at the tele side for a moment instead. Something
like 25-100 would provide a nice overlap, I frequently just want to
bring one lens, but it would have mass, bulk and cost money. As said,
I'm not really all that interested in tele. Besides, tele without image
stabilization seems almost unusable. So, I got this idea:

Buy a Canon 50/1.8 for almost no money and use it as a tele by cropping
the 10 MP high quality picture it delivers. This will (surprisingly)
give all these benefits:

* Worlds cheapest tele lens $100 - On pair with my tele interest.
* Worlds most lightweight tele 130 g - Perhaps it won't stay at home?
* Has image stabilization - F/2 versus F/4 or F/5.6 for the real thing.

Great when you think about it, right? Now, my question is: Will this
work? Is a 50 mm prime so god, that a 2 MP crop actually has resolution
close to 2 MP? Will a resampled (2 MP) full-frame image from a real
tele be significantly sharper, or only slightly better? Can handheld
(w/o IS) at F/4 really compete with a F/2 50 mm crop with respect to
camera-shake?
/Bengt

Think about perspective rather than angle of view. Perspective and focal
length go hand in hand.

I'was thinking they would be equivalent, as the view angle is the same for
a crop and a true tele. But you're right. I forgott a true tele will let
you shoot from a further distance, changing the perspective for the same
"coverage". This also make this technique useless indoors. You can't come
far enough from the subject. Guess a cheap Tamrom 55-200 is the answer
to my pretty modest tele interest then.
Cheers. /Bengt

Bengt C wrote:
On Sat, 14 Jul 2007 18:44:12 +0200, Wolfgang Weisselberg
Bengt C wrote:

Buy a Canon 50/1.8 for almost no money and use it as a tele by cropping
the 10 MP high quality picture it delivers. This will (surprisingly)
give all these benefits:

* Worlds cheapest tele lens $100 - On pair with my tele interest.

Tamron's 55-200 is in the same price class and needs less
cropping.

Correct. But a F/2 50 mm prime can do other thing better. Things that I'll
do more often than shooting at say 135 mm focal length.

Like low light shooting.

Can handheld (w/o IS) at F/4 really compete with a F/2 50 mm crop with
respect to camera-shake?

If you crop the f/2 50mm shot to the same view angle as the
tele, and downsize the tele to your 2MPix, camera shake will be
identically good or bad for both, ...

How can that be so?

Same view angle, same susceptibility to camera shake.

A (budget) tele will only provide say F/4 at best.
I.e. in a situation where the prime will shoot at 1/250 s the tele will
shoot at 1/60 s or even slower.

Yes .... but let's have a look at
http://www.photozone.de/8Reviews/len...0_18/index.htm
.. If you shoot wide open, you get a center resolution of
1690 LW/PH on a 350D (that would be 845 black and 845 white
lines still resolved at MTF50, i.e. contrast is halved)

Let us assume that you get similar results from your 400D, so
you get 1690 LW/PH on 2592 pixels, ergo 756 lines (378 line
pairs) on your 1736 x 1160 image. That's not very much.

With the 400D, cropping from 3888 x 2592 to 1736 x 1160, you
get a crop factor of 2.23, i.e. a 50mm on your 400D would have
the same view angle after cropping as a 112mm lens on your 400D
(or said the other way: the 50mm on your 400D has natively the
viewangle of an 80mm lens on a 35mm camera and after cropping a
viewangle of a 179mm lens on a 35mm camera.)

So let's compare it to the Sigma AF 18-125mm f/3.5-5.6 DC
http://www.photozone.de/8Reviews/len...3556/index.htm
(note the "Verdict" at the end about AF failing below 50mm before
rushing to buy one). At 125mm, f/5.6, the border only has 1437,5
LW/PH. Scaling down to 2MPix, you of course retain the resolution
until you have less pixels than resolution, hence you get at least
the maximum of 1160 lines (580 line pairs) after scaling down.

Now compare vertically 378 line pairs to 580 line pairs. Over 50%
more.

Ok, so you stop your 50mm down. The best LW/PH reached is
2069 at the center at f/5.6. (Oops, here goes your "faster
lens" argument!) --- and you get 926 LW/PH (463 line pairs).
Still 25% advantage to the mediocre border resolution of the
18-125mm.


So basically, cropping even from a very good lens does not get
better results than downsampling from a mediocre lens that's got
the right focal length. I would advise against it.


...but the tele image will have all information and less noise in the
bargain. You gain 2 stops, but on the tele you can up the ISO 2 stops
and still get no worse noise in the end result, so yes.

Are you sure a 1600 ASA tele does outperform a 50 mm crop at 400 ASA?

Quite sure, yes. Even a mediocre tele, see above, outdoes
cropping, and if you don't stop down the 50mm, you'll be in
even worse problems. And you don't gain much by it regarding
focal length.

Once you throw in a tripod, mirror up condition and a remote
release, the 50mm is soundly beaten.

Of course. But, as I said before, weight (and bulk) matters and the
50 mm prime beats the tripod by an order of magnitude here.

As a 50mm prime, sure, as a tele lens, nope.

...I consider a 1-2 MP picture "usable" and 3-4 MP "sufficient". My
first digicam, a 1.3 MP Canon A50,

1.2 Mio effective pixels, 1/3" sensor, CYGM-Bayer on CCD.
Can do RAW.

took lovely pics, but only under certain (rare) conditions.

The same is true for all cameras, though they have been working
on broadening these conditions for a century or more.

I wonder whether 2 MP crops from my current
XTi with a F/2 prime will produce images comparable (better?) to that
camera. The XTi has, for instance, much better dynamic range.

It'll deliver better crops, especially regarding noise etc.

"much better" depends a lot on post processing, for example.

-Wolfgang

Bengt C wrote:


...I consider a 1-2 MP picture "usable" and 3-4 MP "sufficient".

Sufficient for what, printing nothing larger than 4x6s and/or posting
cheesy pictures to the web?

Greg
--
The ticket******* Tax Tracker:
http://www.ticketmastersucks.org/tracker.html

Dethink to survive - Mclusky