Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
02-10-2010, 03:07 AM   #31
Veteran Member




Join Date: Jan 2009
Location: Canada
Posts: 1,255
QuoteOriginally posted by Laurentiu Cristofor Quote
Actually, on second thought, I don't think the tint is due to a curved focal plane - must be just CA.
How about, both?

Chromatic aberrations

02-10-2010, 04:05 AM   #32
Pentaxian




Join Date: Jun 2008
Location: Flyover America
Posts: 4,475
QuoteOriginally posted by PentaxPoke Quote
Considering the price of the FA35, I can't imagine a lens with a better sharpness/cost ratio.
Even NOT considering price it is still one of the best available.
02-10-2010, 10:09 AM   #33
Veteran Member
Laurentiu Cristofor's Avatar

Join Date: Nov 2009
Location: WA
Photos: Albums
Posts: 3,044
QuoteOriginally posted by asdf Quote
How about, both?
Thanks for the link. Could be. But they don't seem related to focusing differences.
02-10-2010, 01:45 PM   #34
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by Laurentiu Cristofor Quote
What makes you think I didn't? Let's read it together once again:

"tack-sharp images for the obsessed pixel-peeper"
That's not the quote I was referring to. it's this one:

QuoteQuote:
has to be sharp so that later when customer reviews images they can zoom into parts of image reasonably tight without heavy blur.
"Reasonably" tight, without "heavy" bur. Your incorrectly focused shots aside (anyone who has ever used them knows they are capable of far better than your samples show), I maintain that even the kit zooms meet this standard easily.

02-11-2010, 12:48 AM   #35
Veteran Member
Laurentiu Cristofor's Avatar

Join Date: Nov 2009
Location: WA
Photos: Albums
Posts: 3,044
QuoteOriginally posted by Marc Sabatella Quote
Your incorrectly focused shots aside (anyone who has ever used them knows they are capable of far better than your samples show)...
Far better how - far better resolution chart shots? You make it sound like anyone who has ever used them has also shot resolution charts with them.

You can claim my test shots are incorrect, but this is why I initially pointed to the www.the-digital-picture.com comparometer: because their tests illustrate similar issues across many more lenses.

QuoteOriginally posted by Marc Sabatella Quote
That's not the quote I was referring to. it's this one:
"Reasonably" tight, without "heavy" bur.
QuoteOriginally posted by Marc Sabatella Quote
I maintain that even the kit zooms meet this standard easily.
I'm not sure what that standard means, but assuming that its vague definition indicates a level of indifference to those aspects, I agree with you that for such a low standard, most lenses would fit the bill. Let me go even further and say that most lenses, even wide-open, would fit that bill. Now, that's a fitting conclusion to a thread titled "Sharp lens for pixel-peepers??". Let's end on this positive note that should serve as a beacon to every pixel-peeper looking for guidance on the next lens purchase.
02-11-2010, 08:43 AM   #36
Site Supporter
GeneV's Avatar

Join Date: Oct 2008
Location: Albuquerque NM
Photos: Albums
Posts: 9,775
Wow. I feel like I'm watching contract litigation. One group focuses on the first post from the OP and another goes with the second. I would say that the two posts are slightly inconsistent, and both camps are right.
02-11-2010, 06:47 PM   #37
New Member




Join Date: Dec 2009
Location: Miami
Posts: 10
Original Poster
Thanks, a fantastic resource, but not a single lens from Pentax.
Still, the condensed availability of so much information in one page is amazingly helpful.
Thank you for pointing it out to me.
E
02-11-2010, 07:21 PM   #38
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by Laurentiu Cristofor Quote
Far better how - far better resolution chart shots? You make it sound like anyone who has ever used them has also shot resolution charts with them.
Perhaps not, but most of us have shot text much sharper than yours, and comparisons that show little difference at f/8 compared to even the best primes.

02-12-2010, 12:57 AM   #39
Veteran Member
Laurentiu Cristofor's Avatar

Join Date: Nov 2009
Location: WA
Photos: Albums
Posts: 3,044
QuoteOriginally posted by Marc Sabatella Quote
Perhaps not, but most of us have shot text much sharper than yours, and comparisons that show little difference at f/8 compared to even the best primes.
Perhaps, but this is what I got on the 14MP sensor using default settings (no sharpness or contrast boost). I'd be interested in seeing unprocessed results from any Pentax sensor from anyone that did similar shots.

Doing these tests is not easy. First, they can be attacked on many fronts:

- the methodology - it's not focused right, camera is not stabilized, etc
- the subject - if the methodology is good, you can always blame the subject - the lens is a bad sample, etc
- the purpose - if all else fails, bring the heavy artillery - 14MP images are not meant to be observed at 100% - doing that is equivalent to reading a newspaper wrapped around your face

So, it's fun stuff. But really, I'd like to see more shots from anyone, and just to share my experience, this is what I observed in my tests (flawed as they may be)

1) at 100%, even at f/8, the DOF will be thin (the higher the sensor resolution, the thinner the DOF)
2) it's difficult to maintain the same shooting conditions:
- lens perpendicular on chart plane
- lens at same distance from chart plane when testing same focal length
- perfect focus
- same exposure settings
- same lighting
3) Shooting b&w charts produces different results than shooting a normal scene
- it doesn't stress purple fringing weaknesses
- it doesn't show color contrast differences

For my chart tests, I realized it's hard to control all variables, so what I decided to do is to take a series of shots, several with each lens and just try the best. If nothing else, this would be representative of what I would most likely get with my shooting style from those lenses. I used LiveView to maintain the same focusing method across all lenses (the primes I used are manual focus). I fixed the exposure settings and I shot under daylight with overcast sky with AWB. I always tried to focus on the "50" in the middle chart using the top magnification. The end results were that overall the primes came out as looking cleaner than the zooms. In some cases the difference was minimal - I expected the K200 to be much better than the DA50-200@200 but it's only minimally sharper. But this type of difference that I've noticed between zooms and primes is also present in many other shots from the-digital-picture.

Combining those resolution tests with other regular shooting, these were my overall conclusions:

- the old primes are more susceptible to purple fringing and have less contrast
- the M40 is sharper than it is given credit for
- the K200 is not much sharper than the DA50-200
- the zooms don't show purple fringing and have better contrast
02-12-2010, 02:42 AM   #40
Pentaxian
er1kksen's Avatar

Join Date: Oct 2008
Location: Forestville, NY
Photos: Gallery | Albums
Posts: 1,683
If we're discussing cost-sharpness ratio, I'm inclined to toss the M 50mm f1.7 into the mix. Thirty-five bucks, and it's the sharpest lens I've ever owned, and I've owned some highly reputed glass. Wide open it's sharper than the kit zooms get at any aperture, and stopped down just a little bit it easily matches anything else I've used.

I am a compulsive pixel-peeper with regards to sharpness. I use this lens wide open the vast majority of the time.
02-12-2010, 04:13 AM   #41
Veteran Member




Join Date: Dec 2006
Location: Copenhagen
Photos: Gallery
Posts: 1,845
The A* 85/1.4, was tested by a Canon site, as being sharper than the Canon 85/1.2 L lens. But it will be beyond your set price range.
For a excellent zoom, the FA* 28-70/2.8 was found by a Danish magazine as delivering better and sharper images in a studio shot, compared to a good medium format setup they had.

FA 50/2.8 is one of the sharpest lenses Pentax has produced. As have been mentioned, macro lenses also can perform perfectly as ordinary tele lenses.

Whatever you do remember Mirror Lock Up, remote or timed release, and using a heavy-duty stable tripod.

Here are some Measured Resolution Numbers from the Boz site :
“Two serious Pentax users have undertaken the tremendously demanding job of testing the resolving power of variuous Pentax lenses. This is a complicated task with an astonishing number of variables, and conduxting multiple test so that the results are meaningful requires choosing one fixed value for each variable and holding it constant over all tests.
Our two testers work independently, and for some of the setup variables they have chosen different values from each-other. As a result, it is safe to compare the resolution tests by the same tester, but no conclusions can be drawn by comparing the resolution results produced by different testers. Still, the data is very valuable, and a summary of the resolution tests is presented here. The full details can be found on the Web pages of the individual testers”.
Measured Resolution Numbers




QuoteOriginally posted by asdf Quote
Dedicated macro lenses have a flat field of focus and are sharp, so you won't get surprises in the borders and corners or when shooting flat products. So you may still want a macro lens for non-macro work. Although, nothing is sharper (in the center at least) than the FA limited lenses, DA* 55 and FA 50 (and similar fast fifties)...at ~f/4. But with digital, because of the Bayer pattern of sensors and the anti-aliasing filter, all images straight out of RAW will be a bit blurry at the pixel peeping level.
Good tips.


People recommending the Canon 300/2.8, obviously haven’t read through all the posts by the OP in the thread. He explicitly stated that wanted focal distance around the 35-75mm.
(300/2.8 is seldom used for studio shots, so such a recommendation doesn't fit with any of the OP's posts, unless stared blind at the title)

Last edited by Jonson PL; 02-12-2010 at 04:22 AM.
02-12-2010, 06:43 AM   #42
Pentaxian
audiobomber's Avatar

Join Date: May 2008
Location: Sudbury, Ontario
Photos: Albums
Posts: 6,684
QuoteOriginally posted by Laurentiu Cristofor Quote
the higher the sensor resolution, the thinner the DOF
Sensor size affects DOF, but resolution? I've never heard that before, and I can't see why it would be true. I believe all 1.5X crop sensors give substantially equal DOF (there may be miniscule differences due to pixel layout).

I agree with you about the inherent problems with doing these comparison tests but I enjoy looking at the results of my own and others' tests, and I enjoy the critique provided by onlookers. I know from personal experience that it's a bit tough when one is in the hot seat. Personally, I don't care for the 18-55. Even the 18-55 DAL, which is a compact, colour matched fit on my K-x, went straight back into the box.

As to the original question, I can highly recommend the FA 35mm for this purpose. I don't own a D FA 50mm macro but I believe it would also be an excellent choice.
02-12-2010, 08:32 AM   #43
Veteran Member
jsherman999's Avatar

Join Date: Dec 2007
Photos: Gallery
Posts: 8,228
.

Keep in mind that 'sharpness' (acutance) doesn't exactly equal 'resolution', although people often use the terms interchangeably.


Mike Earussi:

QuoteQuote:
Resolution has little to do with perceived sharpness. Sharpness is a function of
edge contrast, not resolution. A low resolultion image can look very sharp
whereas a high resolution image can look fuzzy, low contrast and unsharp. It's a
matter of how the lens has been designed optically--sharpness and resolution
usually being a direct tradeoff, i.e. you can emphasize one only at the expense of
the other. The reason Leica is so famous (and expensive) is that their designers
have seemingly found a way to do both, at least better than anyone else.


Photozone is a fun and useful website in many ways, but he really only gives
resolution figures, whereas what is really needed for a true understanding of a
lens is contrast at various resolutions like MTF charts do. In that area the
Photodo web site is much better as it provides the actual tested MTF curves,
though not for all f stops like Photozone does (I use them both). As such, the
Photozone data can be misleading to those who don't realize their limitations.
.



Here's a definitive read ---> from Luminous Landscape.


To the OP: Pick up a K 35 f/3.5, or M 28 3.5, or A/M/F/FA 50 1.7.

For more money, the FA 35, FA 50 2.8 macro, Sigma 70, Vivitar/Dine/Kiron 105 2.5.



K 35 3.5 wide-open:





.
02-12-2010, 09:23 AM   #44
Veteran Member




Join Date: Jan 2009
Location: Canada
Posts: 1,255
QuoteQuote:
Photozone is a fun and useful website in many ways, but he really only gives
resolution figures, whereas what is really needed for a true understanding of a
lens is contrast at various resolutions like MTF charts do.
As far as I understand it--and correct me if I'm wrong-photozone's charts are directly related to MTF curves: There are infinitely many curves, each depending on x LP/mm. If you consider the intersection of the horizontal line at 50% with these curves (on an ideal MTF chart), you should ideally derive something close to photozone's numbers (you would get x LP/mm at some point in the center, the border and the extreme and then you multiply it by the dimension of the sensor). Although, photozone doesn't account for astigmatism. MTF charts don't account for field curvature...etc.

40 LP/mm curves indicate the ability of the lens to "resolve" detail. 5LP/mm curves tell you about the overall contrast. With the kind of downsampled uncropped pictures people post on the internet, neither matters: the image is downsampled so the first figure doesn't matter; the second figure doesn't matter, because you can easily increase "contrast" (or macrocontrast) in any simple program (or the camera does it to the jpeg).
02-12-2010, 12:02 PM   #45
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
QuoteOriginally posted by Laurentiu Cristofor Quote
Doing these tests is not easy. First, they can be attacked on many fronts:
And that's one reason why you'll note me not rushing to post any of my own :-)

QuoteQuote:
1) at 100%, even at f/8, the DOF will be thin (the higher the sensor resolution, the thinner the DOF)
Which is one reason why shooting resolution charts is sometimes not the best way to get an impression of how the lens will perform in practice. You're seeing only a thin slice of the zone of acceptable focus - which may or may not be the absolute optimum slice - rather than seeing the performance over the whole zone. Differences that might be apparent in that single slice might not be so apparent when judging the entire zone. At least, that seems to me to be a plausible explanation of a phenomenon I've seen play out many times (eg, M85/2 and M100/2.8 performing much better in practice than resolution charts would suggest).

QuoteQuote:
In some cases the difference was minimal - I expected the K200 to be much better than the DA50-200@200 but it's only minimally sharper.
FWIW, I found the same with the M200/4, which one would expect to be no better than the K.
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!
k-mount, lens, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
K-7 video mode and sharpening for pixel-peepers richtrav Pentax DSLR Discussion 0 08-19-2009 12:28 AM
For you pixel peepers... wildman Pentax SLR Lens Discussion 12 01-27-2009 10:33 PM
K200D Noise Performance Chart - Pixel Peepers Rejoice! cputeq Pentax DSLR Discussion 8 06-01-2008 07:04 PM
Wanted! Pixel Peepers - new Sigma 17-70mm superfuzzy Pentax SLR Lens Discussion 9 01-15-2008 07:39 PM
Hay pixel peepers-Help regken Photographic Technique 1 12-02-2007 11:30 AM



All times are GMT -7. The time now is 01:19 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