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02-08-2011, 08:32 AM   #31
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this is all BS

when you consider the change in resolution in sensors between the lowely *istD series at 6 mP and the newest 16 mP camera, the change in sensor "pitch" so to speak, has gone from from 8 microns to about 5 microns.

I seriously doubt any lens which worked well on any DSLR is yet at it's limit optically, or thay you could notice

02-08-2011, 09:22 AM   #32
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QuoteQuote:
when you consider the change in resolution in sensors between the lowely *istD series at 6 mP and the newest 16 mP camera, the change in sensor "pitch" so to speak, has gone from from 8 microns to about 5 microns
.

I'm still waiting for a few shots from a couple new lenses where one demonstrates the lack of resolution in the lens being more than that of the sensor.

Until we have an example, the whole concept of a sensor out resolving a lens is just a concept. Since no one knows if this concept is the result of some lab work somewhere or originated in some marketing department to talk people who buy new cameras in to buying new glass as well, especially relevant in the Pentax community where there is a lot of usable old glass.

It's only with actual photos to compare that a person can make up their mind and decide if this is even an issue for them.

It just seems to me that if the concept was real, someone somewhere would have presented some physical evidence. After all, photography is about producing images, not academic discussions about glass.

So, personally, I'm not entertaining any more discussions about lenses not having enough resolution for digital sensors without some kind of visual evidence. Preferably not visual evidence from one lens that's been knocked around in your camera bag for a few years.

I certainly believe that some lenses are sharper than others. That's not the issue. The issue is finding a lens that is good on film or low res digital, that isn't good on higher res digital, or even a lens that is good on a 6mp that isn't good on a 14 mp.

Any evidence at all will be accepted.

I have the old 18-55 from my *ist and the "new one" that came with my K-x, that's been "improved" for higher resolution... on my K20D I can't tell the difference, even though it's been stated, the old one wasn't good enough for the higher resolution sensors.

Someone prove this is an issue.

Until then.

No one has seen it.
You can't prove it exists.
It doesn't exist.
02-08-2011, 09:40 AM   #33
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I wish I still owned a K10 so I could show you the difference Norm. I don't see it with decent lenses, but I had some pretty bad ones that looked OK on a 6 megapixel sensor (at 100 percent) and looked really bad at 10 megapixels. The only SLRs I have right now are the K20 and K7 which have the same resolution sensor, so I can't post comparison photos to show you.
02-09-2011, 12:19 AM   #34
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QuoteOriginally posted by Lowell Goudge Quote
when you consider the change in resolution in sensors between the lowely *istD series at 6 mP and the newest 16 mP camera, the change in sensor "pitch" so to speak, has gone from from 8 microns to about 5 microns.

I seriously doubt any lens which worked well on any DSLR is yet at it's limit optically, or thay you could notice
Well, you've just identified one difference between the *istD and K-5, that the linear resolution has been improved by nearly a factor of 2.

I think there will be plenty of lenses out there which work reasonably well at 6MP, but will be obviously soft at 16MP. One example will be the Mk.1 18-55 kit lens: Pentax had to improve it in order to be compatible with their new 10MP cameras (at least that's what Pentax said).

Having said that, I'm pretty sure you're right, there are quite a few lenses which are overkill at 6MP, and which are plenty sharp enough for 16MP. But, on the other hand, there are lots of lens shootouts on this very forum in which a 10-12MP camera (say) is used to demonstrate differences in resolution between otherwise decent lenses - especially at larger apertures. This suggests that even "good" lenses are becoming rather borderline at the higher pixel-counts.

02-09-2011, 01:13 AM   #35
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QuoteQuote:
used to demonstrate differences in resolution between otherwise decent lenses
How would you do that?

Do you have any links to such an article?
02-09-2011, 01:54 AM   #36
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QuoteOriginally posted by peterh337 Quote
How would you do that?

Do you have any links to such an article?
I'm not implying that any of the shootouts involved the scientific measurement of absolute resolution, but there have been many, over the years, that show visible differences between lenses.

Here's a fairly recent one:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/121708-50ish-m...t-k-mount.html

Note that the lenses tested here represent pretty much the cream of the crop, resolution-wise, as far as affordable lenses go. Also, some - but not all - of the lenses here seem to have resolution which is too good for the camera (a K-5) to separate, suggesting that they're perfectly adequate for the K-5.
02-09-2011, 02:27 AM   #37
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I am not sure that that review has avoided problems caused by less than great autofocus.

To check lens resolution properly, you need to avoid focus issues, probably by setting up several similar objects staggered slightly in distance, so if the camera is doing a bit of FF or BF, some of them will still end up in the optimal focus.

I've just looked at some pics taken with the ist-DL (with the 16-45 DA) and none of them show visible pixels. However, pics taken with the little Casio EX- cameras easily show the sensor pixels if one zooms in enough. None of my K5 pics show the sensor pixels. This tends to suggest that even the ist-DL was lens limited, which is hard to believe...

The other thing is that for some bizzare reason there are widespread reports of variations between lenses. For sure, I have compared a used 17-70 with a brand new 17-70 which I have just bought, and the latter is much sharper. But this is clearly due to some focus issue with the former one, because it was just fine at F8. How this can happen, given that the focus process is a feedback loop, I have no idea...
02-09-2011, 03:10 AM   #38
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Guys.....the old lenses still work just fine.





Pentax K-5
S-M-C Takumar 105/2.8



02-09-2011, 03:30 AM   #39
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QuoteOriginally posted by Mike Cash Quote
Guys.....the old lenses still work just fine.





Pentax K-5
S-M-C Takumar 105/2.8

mike

thanks

I rest my case
02-09-2011, 06:42 AM   #40
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kh,
35mm film according to the DCI (digital cinema initiative) group claims 4096 (4k) wide digital projectors are equal to 35mm movies. That would be 2,890 dpi. Very close to your 2,700 dpi.
02-09-2011, 06:54 AM   #41
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But isn't MTF more accurate than lp or dpi? I have a crt projector which can show all 1920x1080 pixels of an hd signal. But so can any 1080p digital like DLP. Every single DLP, even the $100 Walmart special, though, will kill my crt for MTF.
02-09-2011, 07:54 AM   #42
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While shooting a wildflower in my house yesterday I did a couple tests with the old Da18-55 that came with my *ist, and the newer DA 18-55 AL that came with my K-x. The old "not enough for a K20D " DA seriously outperformed the newer AL based on about 10 exposures. I'm willing to bet, the actual build of the lens is more important than any resolution test done in a lab for determining what lens is better.

Pentax can a say they redesigned the lens the lens for digital glass, all they want. I have two lenses 18-55 and the older one works better. And when you think about it, that pretty much means nothing. Maybe the camera didn't select the same focus points. Just because I did the same thing both times doesn't mean the camera did. There's an alternate brain in there that can't be trusted to make the same decision twice.

So, all I'm saying is, I had two lenses, most of the testers only tested on one copy. WHy are their results better than mine?

They probably aren't.

You still have to go out and find a copy of the lens you like.

You can read the reviews but, your experience may vary.

And as I said, I'm still not sure this whole issue isn't a marketing ploy.. to sell expensive new glass to people who don't need it.

Or as someone once said "Advertising will sell you things you don't need to impress people you don't like."
02-09-2011, 10:34 AM   #43
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QuoteOriginally posted by Mike Cash Quote
Guys.....the old lenses still work just fine.





Pentax K-5
S-M-C Takumar 105/2.8


I'm with Lowell and Mike on this one. I suspect most if not all of the old Pentax glass with perform well on the K5. We can get carried away with this sort of thing. I'm still saving for a K5 and can't wait to put my old lenses to the test when it arrives.

Tom G
02-09-2011, 05:25 PM   #44
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QuoteOriginally posted by troglodyte Quote
But isn't MTF more accurate than lp or dpi? I have a crt projector which can show all 1920x1080 pixels of an hd signal. But so can any 1080p digital like DLP. Every single DLP, even the $100 Walmart special, though, will kill my crt for MTF.
I just had a Vietnam flashback......well, a "Good Morning Vietnam" flashback.
02-10-2011, 01:20 AM   #45
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Did anyone say that old lenses aren't up to the job? I certainly didn't.

In fact, I would go so far as to say that, as far as resolving power is concerned, vintage glass is at least as good as the modern stuff - particularly in the "easier" focal lengths (especially the 50s).

Where the modern glass wins, though, is in the area of autofocus, colour response, contrast, flare resistance and CA/PF.

My contention is that there are plenty of lenses out there - both modern and vintage - which don't provide the resolution the K-5 deserves.
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