Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-18-2010, 07:37 AM   #31
Junior Member




Join Date: Jan 2010
Posts: 27
Original Poster
I order it , tomorow is in my hands Tamron AF SP 17-50mm f/2.8 XR Di II LD (to bad no VC IF stabilizator available for Pentax )! Now please tell me how to check if its a good copy : good focus, aberations , how to test it in order to send it back if its bad.


Last edited by crossing; 01-18-2010 at 07:42 AM.
01-18-2010, 08:23 AM   #32
Veteran Member
sterretje's Avatar

Join Date: Dec 2008
Location: Roodepoort, South Africa
Photos: Gallery | Albums
Posts: 3,534
VC is Vibration Control and has the same function as shake reduction (according to Tamron - Wikipedia, the free encyclopedia). If that's correct, be glad that it does not have VC as VC and SR will more than likely counteract each other.
01-18-2010, 08:55 AM   #33
Veteran Member
WMBP's Avatar

Join Date: Dec 2006
Location: Dallas, Texas
Photos: Gallery
Posts: 2,496
QuoteOriginally posted by Ash Quote
OK, in case you missed this little bit of info, when we say 'fixed aperture zoom' we don't mean that for example the 17-50 is f/2.8 throughout its focal range - we mean that the 17-50 has a MAXIMUM aperture of f/2.8 throughout its focal range.
Yes, Ash's clarification is important and I apologize for failing to realize that this was perhaps NOT clear. I usually refer to lenses like the Pentax 16-45 f/4 as "fixed aperture zoom lenses". Ash's clarification reminds that my description isn't really correct, if taken literally; but "fixed maximum aperture zoom lenses" is too much of a mouthful.

Will
01-18-2010, 10:27 AM   #34
Junior Member




Join Date: Jan 2010
Posts: 27
Original Poster
QuoteOriginally posted by sterretje Quote
VC is Vibration Control and has the same function as shake reduction (according to Tamron - Wikipedia, the free encyclopedia). If that's correct, be glad that it does not have VC as VC and SR will more than likely counteract each other.
ok ,please tell me how to check if its a good copy : good focus, aberations , how to test it in order to send it back if its bad.

01-18-2010, 12:01 PM   #35
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
Take pictures with it. If you like them, keep the lens.

If you're not already an expert on testing for defects, chances are any attempts at finding defects would only show problems in your testing methods, not lens defects. Another way of saying this: there are far more people conducting tests improperly and getting invalid results than there are lenses with defects worth worrying about. And an Internet forum is not going to be able to make you an expert tester fast enough.
01-18-2010, 12:05 PM   #36
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by crossing Quote
If f2.8 its not fixed ,whats the aperture range on 17-50 TAMRON ?
Not important. The *max* aperture is f/2.8 at all focal lengths, that's all that matters. The minimum aperture has little relevance - you don't normally shoot at minimum aperture unless you like poor image quality and shutter speeds too slow to handhold even in daylight (OK, there are *some* reasons to shoot at minimum aperture, but I guarantee they are not relevant here.

You are confusing the maximum aperture range stated on a lens with the total range of the lens. A lens that says f/2.8 - f/4.5 means its maximum aperture is f/2.8 at the wide end, and its maximum aperture is f/4.5 at the long end. A lens that simply says f/2.8 means its maximum aperture is f/2.8 at all focal lengths. But in all cases, the *minimum* aperture is much smaller - usually in the 20's or 30's. So you can shoot at any aperture you want up to the maximum.
01-18-2010, 03:50 PM   #37
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,264
How I Shoot In Low-Lit Rooms Without A Flash

1) I pull out my Sony DSC-V1 (5mpx) and make sure the battery is charged.
2) I switch it to NightShot, which pulls the IR hot-filter off the sensor.
3) I set the ISO to Auto (or 800, giving an effective ISO of 2500).
4) I insert my little Sony HVL-IRM infrared light into a flash bracket.
5) I power-up everything and fire away stealthily, unhindered.
6) In PP, I have tricks to restore some color to the images.

Oops, none of that is Pentax stuff. Kill me now.

As noted above, low-light photography ain't easy. If it was, everybody would do it, y'know. I recall seeing various books on such work, but I'm too lazy to dig up any titles just now. Of course, there's an easy answer: TRIPOD. Don't leave home without it.
01-18-2010, 10:36 PM   #38
Junior Member




Join Date: Jan 2010
Posts: 27
Original Poster
Why 17-50 Tamron its much more longer in lenght when is extented compare with 18-55 kit lens ?

01-19-2010, 03:25 AM   #39
Veteran Member
sterretje's Avatar

Join Date: Dec 2008
Location: Roodepoort, South Africa
Photos: Gallery | Albums
Posts: 3,534
Tamron spec: 16 elements in 13 groups
Pentax spec: 11 elements in 8 groups

I guess that the 16 elements will take more space.
01-19-2010, 05:30 AM   #40
Site Supporter




Join Date: Mar 2009
Location: Gladys, Virginia
Photos: Gallery
Posts: 16,217
The wider the maximum aperture, the wider (and usually longer) a lens is. If you think that is big, don't look at a 70-200 f2.8 lens or a 300mm f2.8. I have a 16-50 f2.8 and when I first got it, I thought it was big, but once I saw the difference in sharpness in my photos, I was happy to put up with the weight.

As to figuring out if the Tamron is sharp, as Marc said, just shoot with it. If there is something concerning, you can shoot some newsprint with it. The only thing is that you need to make certain that you have the camera exactly perpendicular to it and on a tripod otherwise it can make you think your lens is off.
01-19-2010, 05:52 AM   #41
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
QuoteOriginally posted by Rondec Quote
....
As to figuring out if the Tamron is sharp, as Marc said, just shoot with it. If there is something concerning, you can shoot some newsprint with it.

The only thing is that you need to make certain that you have the camera exactly perpendicular to it and on a tripod otherwise it can make you think your lens is off.
Or, purposefully tilt the paper a bit; That way a band of print will surely be in focus for you to inspect critically. Do this test at f:2.8, as that's what you care about for low light.
01-19-2010, 07:36 AM   #42
Junior Member




Join Date: Jan 2010
Posts: 27
Original Poster
QuoteOriginally posted by sterretje Quote
Tamron spec: 16 elements in 13 groups
Pentax spec: 11 elements in 8 groups

I guess that the 16 elements will take more space.

sigma 18-50 f2.8 macro hsm
have 15 elements in 13 groups and zooms inside.
01-19-2010, 08:54 AM   #43
Veteran Member
sterretje's Avatar

Join Date: Dec 2008
Location: Roodepoort, South Africa
Photos: Gallery | Albums
Posts: 3,534
QuoteOriginally posted by crossing Quote

sigma 18-50 f2.8 macro hsm
have 15 elements in 13 groups and zooms inside.
Thanks for that info.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, dc, kit, lens, pentax help, photography, sigma
Thread Tools Search this Thread
Search this Thread:

Advanced Search



All times are GMT -7. The time now is 07:22 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top