Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-20-2010, 10:51 AM   #16
Veteran Member
Eruditass's Avatar

Join Date: Jul 2009
Location: Pittsburgh, PA
Photos: Gallery | Albums
Posts: 2,206
QuoteOriginally posted by UnknownVT Quote
Hmm... I don't see that....

The apertures at each tested focal length runs down the left column, and the SQF ratings go across from there by size of enlargement (along top row of each focal length).

So 50-200 at 50mm for a 14x11 print
f/4 (max aperture) scores 93.6 in Orange (A rating)
f/8 scores 94.4 in Red (A+rating) as one would expect.....

for a 20x24 print - the gap widens
f/4 = 83.3 in Yellow (B rating)
f/8 = 86.2 in Violet (B+rating)

However I do see in the intermediate focal lengths some minor improvement of the max aperture over f/8 - however the points spread is so minor that anyone would probably be hard to see any actual difference in quality -
that sometimes is the real problem with numbers, where we may quibble over minor absolute numeric differences when we might not be able to see the difference in actual usage/print.

To be honest I tend to just look at the colors for the SQF charts - that seems to give me a quick overview of how the lens performs.

However I will say that I have found the kit zooms (50-200 and 18-55 mk 1) seem to perform really well at wide open - since those are mainly the apertures I shoot at.
I believe I was reading it correctly, but I guess I was looking at the 55-300mm.

20x24:

200mm @ f4.5: 79.2
200mm @ f5.6: 78.6
200mm @ f8.0: 78.1


300mm @ f5.6: 83.3
300mm @ f8.0: 83.2
300mm @ f11 : 82.1

16x24:

200mm @ f4.5: 86.4
200mm @ f5.6: 86.1
200mm @ f8.0: 85.7


Also, it looks better at 300mm than 200mm? This is why I noted the DoF effects coming into play of their ratings since everyone seems to experience worse IQ at 300mm.

Lastly, their trends don't match the enlargement sizes which doesn't make sense to me at all.

At 16x20, 300mm @ f5.6 to f8 increases by .1 instead of decreasing, which is different from 20x24.

The differences aren't large at all, but these inconsistencies put me off of their testing.

01-20-2010, 11:13 AM   #17
Veteran Member




Join Date: Sep 2007
Location: USA
Posts: 1,812
QuoteOriginally posted by Eruditass Quote
Also, it looks better at 300mm than 200mm? This is why I noted the DoF effects coming into play of their ratings since everyone seems to experience worse IQ at 300mm.

Lastly, their trends don't match the enlargement sizes which doesn't make sense to me at all.

At 16x20, 300mm @ f5.6 to f8 increases by .1 instead of decreasing, which is different from 20x24.

The differences aren't large at all, but these inconsistencies put me off of their testing.
Points well observed and taken -
I apologize for missing those by not looking at the numbers closely - only at the colors.

I tend to agree with you -
and obviously cannot explain the apparent inconsistency.
If we really wanted to know - only have to write to PopPhoto and ask?
[EDIT to ADD - I copied and pasted some of Eruditass' figures and posted a query on Respond to Popular Photography forum - Inconsistency in SQF? ]

In the meantime - perhaps some of this might help?

PopPhoto - How We Test Lenses

All I know is that "Popular Photography" has been established for many, many years -
and because it is "popular" there are always going to be a fair number of detractors -
that of course doesn't mean they don't make mistakes -
but usually because of the sheer circulation popularity they are challenged on those mistakes
- so I do tend to put some weight to their findings.

Last edited by UnknownVT; 01-20-2010 at 11:58 AM. Reason: added PopPhoto query link
01-20-2010, 12:01 PM   #18
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by UnknownVT Quote
Not to take anything away from those comments or the quality of the 55-300 zoom -
BUT the 50-200 Zoom actually is of quite outstanding quality.

This is confirmed by reviews eg: PopPhoto review of the 50-200 as the Samsung clone -
the 50-200 SQF chart compare to the 55-300 test
Nice to see this here. Too often people see only the very lukewarm photozone.de review / test of the 50-200 and assume it's the final word on the subject. How muc of this is sample variation and how much is difference in test metholodogy is hard (impossible, actually) to say. But again, nice to have another "objective" data point to counter photozone with.
01-20-2010, 12:25 PM   #19
Veteran Member
Eruditass's Avatar

Join Date: Jul 2009
Location: Pittsburgh, PA
Photos: Gallery | Albums
Posts: 2,206
QuoteOriginally posted by UnknownVT Quote
Points well observed and taken -
I apologize for missing those by not looking at the numbers closely - only at the colors.

I tend to agree with you -
and obviously cannot explain the apparent inconsistency.
If we really wanted to know - only have to write to PopPhoto and ask?
[EDIT to ADD - I copied and pasted some of Eruditass' figures and posted a query on Respond to Popular Photography forum - Inconsistency in SQF? ]

In the meantime - perhaps some of this might help?

PopPhoto - How We Test Lenses

All I know is that "Popular Photography" has been established for many, many years -
and because it is "popular" there are always going to be a fair number of detractors -
that of course doesn't mean they don't make mistakes -
but usually because of the sheer circulation popularity they are challenged on those mistakes
- so I do tend to put some weight to their findings.
Cool, I look forward to their response!

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, cameras, comments, dslr, kx, lens, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
What intriques me about lens comments... pacerr Pentax SLR Lens Discussion 4 08-18-2009 11:55 AM
70-200/2.8 lenses - novice needing advice adamkean Pentax SLR Lens Discussion 21 02-05-2009 04:38 PM
Seek advice: $200+ K110D repair - trade-in? TreeHuggerDoug Pentax DSLR Discussion 7 07-22-2008 10:02 AM
Any comments on the Sigma 24-135mm f/2.8-4.5 lens TedP Pentax SLR Lens Discussion 11 03-22-2007 08:27 AM
Anyone with comments on the Pentax F 35-135mm lens? Vulpix Pentax SLR Lens Discussion 1 03-03-2007 10:35 PM



All times are GMT -7. The time now is 02:45 AM. | 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