Newbie question re. sharpness

Not sure if I missed it in the other posts, but a tripod is a must for
such a test!
- Take photos at smallest F stop and F8 (at least)
- At min, max and middle of the zoom range

Shoot a brick wall/ facade or the like and review the results at 100%
in photoshop.

yes, I also always loved the "Watch out for bad copies."";-)) However,
there are as many results as testers. Someone had a kit lens that was
sharper than his new 24-105 F4L IS if I remember the post correctly. I
would be pi#%d off ;-))


T
http://tr-photo-blog.blogspot.com/


gwperil wrote:
Rudy Benner wrote:
"gwperil" wrote in message
ups.com...
Hi,
I have what is hopefully a pretty basic question. I have a Canon 350D
with the two kit lenses:

* EF-S 18-55mm 1:3.5-5.6 II
* EF 75-300mm 1:4-5.6 III USM

As a test, I tried taking the "same" photo with each lens; that is, I
framed a still object as closely as possible with each lens and used
the same settings: Manual mode, 1/100s, f/5.6, ISO-100, Flash
(Speedlite 430EX pointed ahead), tripod. Obviously I had to move the
camera back to get the same shot with the 75-300. The only other
difference was of course the focal lengths: 45mm vs 75mm.

The picture taken with the 75-300 came out much sharper than with the
18-55. What accounts for that? I ask because, in general, I'm able to
get better looking pictures out of the 75-300.

Thanks in advance!


Can you repeat the experiment without using the flash, use ambient light in
an open area?

Thanks for everyone's comments on this.
I will take the advise of dropping the flash and going outside on a
cloudy day. Then I will find a place to post the photos.

Part of the reason for these tests is that I do not (yet) have the
experience to differentiate between bad technique and inferior
equipment... so as I consider a new lens, I want to measure the quality
of the two kit lenses as a reference point. There are a lot of strong
opinions out there with respect to lens quality. For example, I'm
interested in the EF 28-135mm F/3.5-5.6 IS USM lens. Research is all
over the map: "Perfect walk-around lens." "Way too soft." "IS is a
life-saver." "IS is not worth the money." And my personal favorite:
"Watch out for bad copies." Bad copies? There goes some more hair...

I guess there's no substitute for just plunking down the $$$ and trying
it out.

"t_rust" wrote in message Shoot a brick
wall/ facade or the like and review the results at 100%
in photoshop.

yes, I also always loved the "Watch out for bad copies."";-)) However,
there are as many results as testers. Someone had a kit lens that was
sharper than his new 24-105 F4L IS if I remember the post correctly. I
would be pi#%d off ;-))


Canon DSLRs have a low pass filter in front of the sensor that limits the
resolving power anyway by blurring the image. Any hard black to white
transition seems to take about 3 pixels to occur fully and this is often the
limiting factor in determining lens sharpness.

gwperil wrote:

As a test, I tried taking the "same" photo with each lens; that is, I
framed a still object

A flat object or a 3d object? Are you comparing the center, the edges
or even the corners?

Manual mode, 1/100s, f/5.6, ISO-100, Flash, tripod. 45mm vs 75mm.

Note that f/5.6 is wide open for the 18-55@45mm while it's one stop
down for the 75-300. In general, most lenses perform better one or two
stops down than wide open.

The picture taken with the 75-300 came out much sharper than with the
18-55. What accounts for that?

There are a lot of possible reasons:

* the focus was more accurate with the 75-300 (e.g. try manual focusing
and/or shots at different distances as well.)
* your 18-55mm is not performing to spec due to a manufacturing defect
or damage
* the 75-300@75mm f/5.6 is just sharper than the 18-55@45mm f/5.6

From Canon's published MTF curves, you might expect the 18-55@45 to be
better in the center and the 75-300 better at the edges; but these are
theoretical numbers and in the real world lenses vary.

http://www.usa.canon.com/consumer/co...ode lid=10512
http://www.usa.canon.com/consumer/co...mode lid=7444

To understand more about these charts:
http://www.luminous-landscape.com/tu...ding-mtf.shtml
http://www.luminous-landscape.com/tu...contrast.shtml

I ask because, in general, I'm able to
get better looking pictures out of the 75-300.

That would be my experience as well. The 75-300 Canon lenses I've used
have been pretty good under 150mm.

--
Erik

gwperil wrote:
Part of the reason for these tests is that I do not (yet) have the
experience to differentiate between bad technique and inferior
equipment...

At least you realize the difference. That's 90% of the problem solved!


I want to measure the quality
of the two kit lenses as a reference point.

If you really want to "measure" there are charts and tools that can
help:

http://www.imatest.com/
http://www.normankoren.com/Tutorials/MTF5.html
http://www.graphics.cornell.edu/~wes...res-chart.html

The main problem with these is that they are not used under the same
lighting/distance as most real-world photographs.

For example, I'm
interested in the EF 28-135mm F/3.5-5.6 IS USM lens.

Note that these focal lengths are a bit long on an EF-S 1.6x crop
camera. The 17-85mm is the EF-S equivalent.

Research is all
over the map: "Perfect walk-around lens." "Way too soft." "IS is a
life-saver." "IS is not worth the money."

And guess, what? All of these opinions may be true! A lot depends on
how you use a lens and what you expect (and even what camera you use it
with!).

Bad copies? There goes some more hair...

There are two solutions for this:
1) buy where you can return if not satisfied
2) be able/willing to send in the lens for calibration repair (ideally
under warranty).

I guess there's no substitute for just plunking down the $$$ and trying
it out.

You can also often rent lenses you cannot afford to buy - even via the
internet in the U.S.
http://www.rentglass.com/

--
Erik

wrote:
You can also often rent lenses you cannot afford to buy - even via the
internet in the U.S.
http://www.rentglass.com/


Pretty cool site. The only problem I see:

"In stock: No" on most of the items ... at least, for Nikon.

--
Thomas T. Veldhouse
Key Fingerprint: D281 77A5 63EE 82C5 5E68 00E4 7868 0ADC 4EFB 39F0

On 2006-12-12, Thomas T. Veldhouse wrote:
wrote:
You can also often rent lenses you cannot afford to buy - even via the
internet in the U.S.
http://www.rentglass.com/

Pretty cool site. The only problem I see:

"In stock: No" on most of the items ... at least, for Nikon.

Then sign up for email notification. I'd suspect that the depth of the
notification queue is one factor that might be used to judge whether
buying more copies will be profitable. At least it will tell you how
long you might have to wait for a particular item.

There is also a new competitor: http://www.ziplens.com

A review:
http://photodoto.com/index.php/2006/...ental-service/

(Note: I have not personally used either of these services, but have read mostly positive experiences from those who have.)

--
Erik

Hmm, there are more of these than I knew:

http://www.rentglass.com
http://www.ziplens.com
http://www.lensprotogo.com
http://www.photolensrental.com
http://www.rentcameragear.com

And Adorama also does on-line rentals.

gwperil wrote:
Hi,
I have what is hopefully a pretty basic question. I have a Canon 350D
with the two kit lenses:

* EF-S 18-55mm 1:3.5-5.6 II
* EF 75-300mm 1:4-5.6 III USM

As a test, I tried taking the "same" photo with each lens; that is, I
framed a still object as closely as possible with each lens and used
the same settings: Manual mode, 1/100s, f/5.6, ISO-100, Flash
(Speedlite 430EX pointed ahead), tripod. Obviously I had to move the
camera back to get the same shot with the 75-300. The only other
difference was of course the focal lengths: 45mm vs 75mm.

The picture taken with the 75-300 came out much sharper than with the
18-55. What accounts for that? I ask because, in general, I'm able to
get better looking pictures out of the 75-300.

Thanks in advance!

I've seen the 75-300 compared against a pro lens in the same focal
range and the cheaper less produced pretty mediocre results. If the
18-55 is even worse, I'd start saving for a better lens for the 350
since it does have a good sensor with decent pixel count. In other
words, your current lens set cannot meet what the sensor can offer.

wrote:
Hmm, there are more of these than I knew:

http://www.rentglass.com
http://www.ziplens.com
http://www.lensprotogo.com
http://www.photolensrental.com
http://www.rentcameragear.com

And Adorama also does on-line rentals.

And Calumet if there's one in your town. I've used them, good for 1 day.

Hmmm none of them have a Nikon 28mm f/1.4 AF

In article , Paul
Furman wrote:

wrote:
Hmm, there are more of these than I knew:

http://www.rentglass.com
http://www.ziplens.com
http://www.lensprotogo.com
http://www.photolensrental.com
http://www.rentcameragear.com

And Adorama also does on-line rentals.

And Calumet if there's one in your town. I've used them, good for 1 day.

Hmmm none of them have a Nikon 28mm f/1.4 AF


Pro Photo Supply (I use them), Citizen Photo, and several others, in
Portland, OR. Just goes to show that you can probably find an outfit
to rent to you in any major town you might be in or close to. Develop
a relationship with them, and they will often even waive the deposit
fees and such.


Non-mail order rental is often a better choice, as you can sometimes do
a spur of the moment rental and still get your equipment (I've called
the afternoon before and still been able to rent the lens I
needed/wanted for then next day. Helps if you need it during the week
instead of weekends, because more people want to be out shooting on the
weekends, and the sports photogs rent a lot of equipment on weekends as
well), plus you can inspect it when you pick it up, and make sure that
it is delivered back properly, on time, in person.

--
You need only reflect that one of the best ways to get yourself a
reputation as a dangerous citizen these days is to go about repeating
the very phrases which our founding fathers used in the struggle for
independence.
-- Charles A. Beard