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12-18-2010, 06:14 PM   #1
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DA lens or not DA -- Help Please

I was in a large camera store in Tempe AZ while vacatining in the area and during a discussion with one of the senior staff was told that an older pentax lens can never be as good as a DA lens specially designed for digital sensors. The reason: The digital lens corrects the light through the lens so that the light strikes the sensor at a right angle. Any lens that is not specifically designed for a digitalsensor will allow the light to fall on the sensor at an angle. He claimed that this makes a major difference when producing a print and even on a computer screen.

This is the first I've heard of it and I wonder a) is it true and b) is the difference in the image really significant? For instance, I seem to get cconsistently better and sharper images using my older FA 28-108, F70-210 and FA 50mm f2.8 1:1 macro than any DA lens that I own, especially the 55-300 which gives me consistently poor results at almost any focal length. The Tamron 90mm f2.8 comes close to the 50mm macro, but there is still a difference.

Any comments, suggestions, etc? Am I out to lunch in my assessment of older Pentax lenses?

12-18-2010, 06:30 PM   #2
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QuoteOriginally posted by gsalmins Quote
a) is it true and b) is the difference in the image really significant?
A) Yes, scientifically,

B) No, practically.

I have 2 DA lenses which are very good but do not exhibit less vignetting than my film lenses, which is what is supposed to happen when light does not hit the sensor at a right angle (the light is "lost").

What I do find is that the DA lenses are lighter, cheaper, better at rejecting flare, and exhibit less CA than their film counterparts (the ones I have tried).
12-18-2010, 06:47 PM   #3
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All I know is that the FA 31 and FA 77 do very well on both my K7 and K10....
12-18-2010, 06:55 PM   #4
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Whether or not newer designs take into account some of the aspects of modern DSLR sensors or not, high quality older glass still works exceptionally well with modern DSLR sensors. The statement "an older pentax lens can never be as good as a DA lens specially designed for digital sensors." is a baseless, untrue statement


Last edited by dgaies; 12-18-2010 at 07:04 PM.
12-18-2010, 06:59 PM   #5
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There are more variables than just the DA design being more suited to APS-C dSLRs. Firstly, the DA 55-300 has no film comparison, which is the only way to validate this observation. Secondly, it's pointless comparing a DA 55-300 to a FA 77 or FA 135. There may be a case for comparing the FA 100/2.8 macro to the DFA 100/2.8 macro - but from previous discussions here there's little discernible difference in IQ.

Another very commonly discussed comparison is the DA vs FA limited series lenses. Again, the difference has more to do with colour rendition than anything else.

So no scientific input here, just real-world stuff that is of greater significance.
12-18-2010, 07:03 PM   #6
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QuoteOriginally posted by Ash Quote
So no scientific input here, just real-world stuff that is of greater significance.
This. Don't buy DA because they are better, only buy DA if it is the proper tool for your purposes. Older lenses work fantastically on modern cameras, and many of them surpass their modern counterparts.
12-18-2010, 07:07 PM   #7
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I understand that this is an issue in m4/3 lens design.

But I also note many m4/3 users snapping up old analog glass.

And I don't see my DA18-55@24 outperforming my Vivitar-Komine 24/2.

So maybe it doesn't matter much. Get out there and SHOOT!
12-18-2010, 07:08 PM - 1 Like   #8
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QuoteOriginally posted by gsalmins Quote
I was in a large camera store in Tempe AZ while vacatining in the area and during a discussion with one of the senior staff was told that an older pentax lens can never be as good as a DA lens specially designed for digital sensors. The reason: The digital lens corrects the light through the lens so that the light strikes the sensor at a right angle. Any lens that is not specifically designed for a digitalsensor will allow the light to fall on the sensor at an angle. He claimed that this makes a major difference when producing a print and even on a computer screen.

This is the first I've heard of it and I wonder a) is it true and b) is the difference in the image really significant? For instance, I seem to get cconsistently better and sharper images using my older FA 28-108, F70-210 and FA 50mm f2.8 1:1 macro than any DA lens that I own, especially the 55-300 which gives me consistently poor results at almost any focal length. The Tamron 90mm f2.8 comes close to the 50mm macro, but there is still a difference.

Any comments, suggestions, etc? Am I out to lunch in my assessment of older Pentax lenses?
You know, maybe this has something to do with them wanting to sell you some lenses?

12-18-2010, 07:16 PM   #9
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QuoteOriginally posted by Douglas_of_Sweden Quote
You know, maybe this has something to do with them wanting to sell you some lenses?
And now I think we have the "real" answer. Good point.
12-18-2010, 07:19 PM   #10
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Oh my Gosh! Glad I know that now. Wonder if anyone, after reading the truth here from the saleman, will want to buy my worthless SuperTak 55/1.8 or 50/1.4?
12-18-2010, 10:31 PM   #11
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Thanks for all the input. The only reason \i posted the question is because the guy in TEmpe was so adamant about yhee difference in IQ. Though my background is engineering and science, when it comes to photography I prefer my subjective opinion of an image. Back home \i have a large shelf loaded with old glass that I have fun with. From time to time I sell some and then buy some more. I have some favourites that I'll never part with like a Series 1 Vivitar by Komine, ver 3, light falling on the sensor at an angle notwithstanding. My DA 55-300, though will be on the market.

My basic approach to photography is to have fun, take lots of photos, walk around with eyes open and then spend a little time sorting and improving in Lightroom. I've been a \pentax guy since \i bought my first SV in 1964 (still have it). So over the years \i've gone through a lot of glass. I'm still a relatively recent convert to digital and have a lot to learn, especially how to make the best use of White Balance settngs. I seem to get an unwanted amount of blue in some of my photos.
12-19-2010, 05:58 AM   #12
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QuoteOriginally posted by gsalmins Quote
Thanks for all the input. The only reason \i posted the question is because the guy in TEmpe was so adamant about yhee difference in IQ. Though my background is engineering and science, when it comes to photography I prefer my subjective opinion of an image. Back home \i have a large shelf loaded with old glass that I have fun with. From time to time I sell some and then buy some more. I have some favourites that I'll never part with like a Series 1 Vivitar by Komine, ver 3, light falling on the sensor at an angle notwithstanding. My DA 55-300, though will be on the market.

My basic approach to photography is to have fun, take lots of photos, walk around with eyes open and then spend a little time sorting and improving in Lightroom. I've been a \pentax guy since \i bought my first SV in 1964 (still have it). So over the years \i've gone through a lot of glass. I'm still a relatively recent convert to digital and have a lot to learn, especially how to make the best use of White Balance settngs. I seem to get an unwanted amount of blue in some of my photos.
Sorry for being so sarcastic. My response to comments like the one your saleman made is that the user is the largest variable not the equipment. With your experience with a range of older glass, all in the Pentax system too!, you might be one of the people that could really appreciate any subtle differences in a lens made for digital sensors over the older film format lens.

Perhaps I am missing something but I keep reading, really, but I keep seeing that the optical formula for certain lines of lenses has been unchanged over the years. For example, I read that the Fast 50 lineup has the same optical formula from the M series through the FA series. Now, if I read that wrong or read a misinformed writers post please correct me, but if that is true how can the salesman be correct?
12-19-2010, 10:38 AM   #13
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QuoteOriginally posted by Douglas_of_Sweden Quote
You know, maybe this has something to do with them wanting to sell you some lenses?
QuoteOriginally posted by dgaies Quote
And now I think we have the "real" answer. Good point.
+1 to all this! Why would a salesman possibly want you to walk out of his store more excited about buying anything other than what he has in stock? Forums and other resources like this make it very easy for my "BS-o-meter" to go off when someone's trying to sell me on something I don't need. I'm often more informed than the camera salesman in most places I visit! (Except for The Camera Store in Calgary - they're VERY good. They're also about the only folks who don't wrinkle their nose or send out any bad vibes whatsoever when you tell them you're a Pentax shooter.)

And being an FA owner as well, I can echo others' sentiments about there being no visible difference in image quality. The only bad photos I ever take are due to user error - my DA and FA lenses are perfectly fine.
12-19-2010, 11:28 AM   #14
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Ask the salesman why Ned Blundell uses and likes FA Limiteds on his K-5?

cheers

Neil
12-19-2010, 12:19 PM   #15
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I thought the salwsman (who also apparently teaches photo classes) was technically right in saying the light from older lenses hits the sensor at an angle but in terms of what the eye can see even on a big blowup it becomes irrelevant. So I posted to get some confirmation - and got it.
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