Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Pentax Lenses

Reply
 
Thread Tools Search this Thread
Old Jan 20, 2007, 2:03 PM   #1
Senior Member
 
nznhut's Avatar
 
Join Date: Nov 2004
Posts: 303
Default

I have also posted this on the DP Review site.

http://imageevent.com/mduke/lenstests/tamronvspentax

This is my own unofficial test of the following lenses:

Tamron 70-300 LD Di AF Macro
Pentax DA 50-200
Tokina AT-X 100-300 MF

I wanted to see how these lenses worked alone and in combination with these two teleconverters:

Tamron 1.4 MC 4 AF
Pentax 1.7x AF Adapter

These photos were taken from my front porch, all on a tripod, trying to get the same frame.

General observations without judgment on picture quality:
1) The Tamron lens is light and fairly easy to handle
2) The DA 50-200 combos are also light, but AF on both converters tends to hunt a bit, particularly the Pentax 1.7x
3) The Tokina is very solid and very heavy

I have tried to add a description to each photo which summarizes the shooting parameters. You can view the exif data details at the bottom of each picture.

I have some preferences of my own, but would very much like people to view them and come to your own conclusions about the different combinations. I would really appreciate your feedback and observations.
Thanking you in advance!
nznhut is offline   Reply With Quote
Sponsored Links
Old Jan 28, 2007, 6:12 AM   #2
Senior Member
 
Hayward's Avatar
 
Join Date: Jan 2007
Posts: 1,318
Default

Except that it doesn't report the 1.4 mag to the K10D IS, I have been quite happy with the Tamron 1.4 MC 4 AF in combo with the SIGMA 70-300mm on my K10D.

IS might be sightly better if camera thought it a 675mm rsather than 480mm, but still some rather amazing shots even at like a 1/60th at full 675mm zoom.

Also dispite Tamerons claim of AF problem with less than a 2.8 lens (its 5.6 at full zoom)... no noticeable AF problems even in low light on the K10D vs without it.
Hayward is offline   Reply With Quote
Old Jan 28, 2007, 7:09 PM   #3
Member
 
Join Date: Nov 2006
Posts: 42
Default

Hayward wrote:
Quote:
Except that it doesn't report the 1.4 mag to the K10D IS, I have been quite happy with the Tamron 1.4 MC 4 AF in combo with the SIGMA 70-300mm on my K10D.

IS might be sightly better if camera thought it a 675mm rsather than 480mm, but still some rather amazing shots even at like a 1/60th at full 675mm zoom.
Hayward,

I agree: I wish that, at a minimum, the PRESENCE of the converter were included in the EXIF data. I am not sure that the converter truly changes the focal length, in fact, I'm pretty sure it does not. It MAGNIFIES what the lens is seeing, which I suspect does not have quite the same effect as actually extending the telephoto lens's focal length. I keep meaning to do some tests of this, but I'm pretty sure that has to be right. So 300 + 1.4x doesn't really = a 420mm lens, although perhaps it's a quibble.

But I'm confused by your math. 300 * 1.4 = 420. 300 * 2 = 600. Where did you get 675mm?

Will
Polytrope is offline   Reply With Quote
Old Jan 29, 2007, 10:11 AM   #4
Senior Member
 
ennacac's Avatar
 
Join Date: Mar 2005
Posts: 4,198
Default

Polytrope wrote:
Quote:
Hayward wrote:
Quote:
Except that it doesn't report the 1.4 mag to the K10D IS, I have been quite happy with the Tamron 1.4 MC 4 AF in combo with the SIGMA 70-300mm on my K10D.

IS might be sightly better if camera thought it a 675mm rsather than 480mm,
Hayward,

I agree: I wish that, at a minimum, the PRESENCE of the converter were included in the EXIF data. I am not sure that the converter truly changes the focal length, in fact, I'm pretty sure it does not. It MAGNIFIES what the lens is seeing, which I suspect does not have quite the same effect as actually extending the telephoto lens's focal length. I keep meaning to do some tests of this, but I'm pretty sure that has to be right. So 300 + 1.4x doesn't really = a 420mm lens, although perhaps it's a quibble.

But I'm confused by your math. 300 * 1.4 = 420. 300 * 2 = 600. Where did you get 675mm?

Will
I am confused about the 675mm also but your idea about the focal length is correct, it is a magnification factor that makes the image look like a focal length of 1.7/1.4 since the TC's are too sort to change the actual FL by that much.

I have found that all TC's degrade the image a bit, some more than others, but the good ones will give great resuts with good lenses.

Tom
ennacac is offline   Reply With Quote
Old Jan 30, 2007, 12:19 AM   #5
Senior Member
 
Hayward's Avatar
 
Join Date: Jan 2007
Posts: 1,318
Default

Very simple a 300mm lens on a crop (ACPS sized) sensor is alrready a 1.5 magnification/crop factor (lookes at just the center of the cast lens image not all of it.)

So plus 1.4x extender 300mm crop = 450mm (as is) x1.4 = 675mm
Hayward is offline   Reply With Quote
Old Jan 30, 2007, 10:43 AM   #6
Senior Member
 
ennacac's Avatar
 
Join Date: Mar 2005
Posts: 4,198
Default

Hayward wrote:
Quote:
Very simple a 300mm lens on a crop (ACPS sized) sensor is alrready a 1.5 magnification/crop factor (lookes at just the center of the cast lens image not all of it.)

So plus 1.4x extender 300mm crop = 450mm (as is) x1.4 = 675mm
There is no 1.5 magnification factor, just a crop factor, so you are mixing apples and oranges by including the 1.5 crop with the 1.4 magnification of the TC.

Tom
ennacac is offline   Reply With Quote
Old Feb 4, 2007, 7:00 AM   #7
Senior Member
 
Hayward's Avatar
 
Join Date: Jan 2007
Posts: 1,318
Default

Well seems to work out that way exposure wise.... as well as recorded image

And as far as the IS.... you are 1.4 mag'ing what it thinks it is corecting for likely not as well as it might if it did see it as a 675 vs 450mm.

Sort of semantics.... as far a "jiggle comp factor" goes mag and FL are about the same thing as far as how the sensor sees the image/body for FL moving around..
Hayward is offline   Reply With Quote
Old Feb 5, 2007, 12:59 PM   #8
Senior Member
 
snostorm's Avatar
 
Join Date: Jan 2004
Location: Chicago Suburb, IL, USA
Posts: 2,770
Default

Hayward wrote:
Quote:
IS might be sightly better if camera thought it a 675mm rsather than 480mm, but still some rather amazing shots even at like a 1/60th at full 675mm zoom.
Hi Hayward,

The problem with your thinking here is that Pentax's SR is calibrated to lens focal length as opposed to crop factor equivalent.

But you are correct that Pentax should allow for the use of TCs by making it possible to manually enter a FL when you use a TC. They could do this by adding a custom menu setting to allow SR to be manually overridden for TC use just as they have the option to allow aperture ring use. Users with TCs could set this up while non TC users can have things as they are.

Scott
snostorm is offline   Reply With Quote
Old Feb 6, 2007, 8:46 PM   #9
Junior Member
 
Join Date: Dec 2004
Posts: 19
Default

I've looked on the test photos and here are my two cents:

The Tamron appears to be sharper than the Tokina despite the price difference. The TC definitely degraded the images made using the Pentax lens.
sjlivson is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 6:11 PM.