Lower-end Canon lenses verses Pentax

[Hayward]

JohnG wrote:

By the way - I'm not bashing the made-for-digital lenses at all. The concept makes great sense - why put more glass in there then you actually need. I'm just saying I think you're worrying over nothing. Heck, all those great Pentax lenses you can get cheaply are full frame.

Well and there is the downside of "Digital" lenses, sooner or later (like a couple of years now) all DSLRS will be full frame.... you want to rash most of your lens collection for saving a few bucks now?

And agin why I like Pentax's attitude of OLD isn't bad (vs C&N Sony like attitude of keep everything as proprietary and obsolete as possible)

An Pentax is unfortunately making DA lenses now too.... but knowing what is coming not far down the road, I really (other than kit one) really want nothing to do with them.

Not that there won't always be sub FF DSLR's.... but they will be what high end P&S are now....

AND again those lenses will be useless at that point... so no thank you if I can avoid it.... REALLY I'd rather have an old Pentax-A MF before a DA. Of course all the SHORT SIGHTED see it as cost saving otherwise Big $$$$$ lens they have bragging rights to for the moment.... but how about when a few years down the road when they are relative garbage and ONLY saleable to the very bottom end?

And again for the moment cheap but (Though Pentax K popularity is changing that fast) those 30+ year old Pentax lenses actually have value as a serious and quality lenns if you don't mind lack of some auto functions.

That Will NOT LIKELY be the case with DA class lens.es when in a few years most DSLR's will mostly all be FF.....

Oh I hear NAY SAYERS.... well consider in little more than a DECADE we have gone from wow 640x480 is really cool...to 12MP and still climbing fast.

My guess it wil even be by the time in a few years from now I am ready to replace my Pentax K10D (Considering I have yet to not have a generationally leaping cameras over that type gap 5 times in that past decade or so.)

[Contriver]

Hayward wrote:

JohnG wrote:

Well and there is the downside of "Digital" lenses, sooner or later (like a couple of years now) all DSLRS will be full frame.... you want to rash most of your lens collection for saving a few bucks now?

And agin why I like Pentax's attitude of OLD isn't bad (vs C&N Sony like attitude of keep everything as proprietary and obsolete as possible)

An Pentax is unfortunately making DA lenses now too.... but knowing what is coming not far down the road, I really (other than kit one) really want nothing to do with them.

Not that there won't always be sub FF DSLR's.... but they will be what high end P&S are now....

AND again those lenses will be useless at that point... so no thank you if I can avoid it.... REALLY I'd rather have an old Pentax-A MF before a DA. Of course all the SHORT SIGHTED see it as cost saving otherwise Big $$$$$ lens they have bragging rights to for the moment.... but how about when a few years down the road when they are relative garbage and ONLY saleable to the very bottom end?

And again for the moment cheap but (Though Pentax K popularity is changing that fast) those 30+ year old Pentax lenses actually have value as a serious and quality lenns if you don't mind lack of some auto functions.

That Will NOT LIKELY be the case with DA class lens.es when in a few years most DSLR's will mostly all be FF.....

Oh I hear NAY SAYERS.... well consider in little more than a DECADE we have gone from wow 640x480 is really cool...to 12MP and still climbing fast.

Very good point Hayward, I was aware that full frameswill probably bethe norm eventually (probably sooner rather than later), but I honestly failed to put this into the equation. I didn't "put two and two together" and realize that when/if full frame becomes the norm you will need full frame lenses. IMO you raise a very important consideration. Although, on the otherhand,with the rate of progress of technology I wouldn't be surprised to see a 1/2.5" sensor PS camera in five years that rivals our current dSLRs.

[JohnG]

Hayward wrote:

Well and there is the downside of "Digital" lenses, sooner or later (like a couple of years now) all DSLRS will be full frame.... you want to rash most of your lens collection for saving a few bucks now?

I'm not sure I agree here. Right now, Canon is the only manufacturer actively marketing anything larger than APS-C sensor (they have APS-H which is 1.3 and full frame). Even Canon continues to produce digiital only lenses for aps-c size sensors. So, I think its way too early to ring the bell on aps-c sensors. Every indication from all the manufacturers is that they are committed to this format for the long term. Sure that could change but there is no reliable indication that it's going to.

As image quality and noise performance continue to improve in the aps-c and 4:3 sensors there will be less call from the masses for larger sensors which require larger cameras and larger lenses and thus more money.

Now, I chose full frame lenses because I fully intended to move up to Canon's 1.3 crop cameras. But I haven't seen anything anywhere that suggest Pentax is moving towards full frame. So, in THAT system I wouldn't discount the digital only lenses either.

[TCav]

Contriver wrote:

However, now I have learned that newer lenses are specifically designed to work with digital sensors and that theytypically outperform the older lenses. So, considering this, Iaskedthe questionif you only consider Pentax lenses that are actually designed for digital sensors, is the Pentax still the very affordable deal I thought it was? And, additionally, I wonder howlong (and how many)Canon has sold lenses designed for digital sensors. I assume that Canon has been making lenses designed specifically for digital sensors for much longer than Pentax has, thus I would figure that there are many more used Canon made-for-dSLR lenses than used Pentax made-for-dSLR lenses. If this is the case, when looking at usedmade-for-dSLR, I wonder if perhaps Canon would actually be at worst the same cost to buy (used made-for-dSLR)lenses for.

Again, you're seeking a valid comparison between apples and oranges.

Digital image sensors happen to be more reflective than film, so there is the potential for an additional source of flare when light reflects off the image sensor, and reflects off the rear surface of the lens, back toward the image sensor. In order to deal with this, "made for digital" lenses simply have a non-reflective coating on this last optical element. This is true for both Canon and Pentax lenses.

But Pentax also has an additional criterion for their "made for digital" lenses. While Canon dSLRs have different size image sensors, ranging from so-called "full frame" sensors (24mm x 36mm, an entirely arbitrary size that holds no special meaning asside from it's longevity) to 1.6 crop factor sensors, while Pentax has adopted a 1.5 crop factor image sensor for all their dSLRs. So their "made for digital" lenses only need to be good enough to produce an acceptable image on this smaller sensor.

So it could be argued that a Canon "made for digital" lens on a 1.6 crop factor dSLRmight outperform a Pentax "made for digital" lens, because the Canon lens is designed to perform adequately on a full frame dSLR, and the 1.6 crop factor dSLR would only be using the lens's "sweet spot".

Contriver wrote:

... and that theytypically outperform the older lenses ...

There is no data to support that assertion.

Contriver wrote:

... I failed to realize the complexity of all the various factors when it comes to dSLR photography.

'nuff said.

[JohnG]

TCav wrote:

Digital image sensors happen to be more reflective than film, so there is the potential for an additional source of flare when light reflects off the image sensor, and reflects off the rear surface of the lens, back toward the image sensor. In order to deal with this, "made for digital" lenses simply have a non-reflective coating on this last optical element. This is true for both Canon and Pentax lenses.

But Pentax also has an additional criterion for their "made for digital" lenses. While Canon dSLRs have different size image sensors, ranging from so-called "full frame" sensors (24mm x 36mm, an entirely arbitrary size that holds no special meaning asside from it's longevity) to 1.6 crop factor sensors, while Pentax has adopted a 1.5 crop factor image sensor for all their dSLRs. So their "made for digital" lenses only need to be good enough to produce an acceptable image on this smaller sensor.

So it could be argued that a Canon "made for digital" lens on a 1.6 crop factor dSLRmight outperform a Pentax "made for digital" lens, because the Canon lens is designed to perform adequately on a full frame dSLR, and the 1.6 crop factor dSLR would only be using the lens's "sweet spot".

TCAV,

I believe you overlooked something in your assessmemnt and it's a good point to bring up. 'made for digital' is a bad term. There are two concepts at play here:

1. Special coatings - which is what TCAV spoke about. These special coatings can be applied to full size lenses or 'digital sized' lenses. As an example, in the Sigma line of lenses, anything with DG in it has the extra coating.

2. Lens is actually sized for digital sensors. This is where I think your oversight was TCAV. The Canon EF-S lenses are sized to work on the 1.6x cameras. They are NOT sized to work on the APS-H (1.3 crop) or full frame cameras. So the new 17-55 2.8 EF-S lens is designed to work only on the APS-C sensor cameras - it doesn't have a large enough image circle for the APS-H or full frame cameras. Following the Sigma example, their lenses with a DC designation are sized specifically for smaller frame cameras.

SO for sigma the 24-70 2.8 DG lens has the digital coating but it's still sized for full frame use. The Sigma 10-20 EX DC lens is sized ONLYfor smaller sensor cameras (1.5 or 1.6 crop). All the DC lenses, by design, will include the coating.

But getting back to your statement, TCAV, - the Canon "made for digital' lenses fit into category 2 above - the lenses are designed to create an image circle for aps-c sensors (and they presumably also have extra lens coatings). The same is true of Nikon I believe. I think third party manufacturers are the only ones that made and market the category 1 type of lens (i.e. lenses designed for full frame with just a digital coating).

[peripatetic]

Hayward wrote:

Yup same with Pentax.... just you can also use all the lenses that virtually go back to just post WWII Japanese reconstruction emergence of these companies too. Canon (nor youngster in the US Nikon) CAN'T say that. (Though ODDLY enough there ARE (3rd party of course) PENTAX M42 adapters for BOTH.... so even the Big Boys appreciate the old Pentax glass)

And by the way AF is often as much a hiderence as it is a help, so personally especially with a prime lens MF is no big issue.... really preferable in a DOF complex shot.
(Where AF often irritatingly screws up)

My point was that even though you can use really old Pentax lenses, so what? It's not like it gives you more to choose from, Canon has made more lenses since 1987 than Pentax in its entire history. Old lenses are not better they're just older. Some are good some are rubbish, some are full of mold, most are broken.

AF as much a hindrance as a help? Eh? What are you talking about?

[peripatetic]

TCav wrote:

There is no data to support that assertion.

I think there is a great deal of data to support that assertion:

At a given price point crop digital lenses far outperform their FF ancestors in MTF, and often in other areas too.

[TCav]

JohnG wrote:

But getting back to your statement, TCAV, - the Canon "made for digital' lenses fit into category 2 above - the lenses are designed to create an image circle for aps-c sensors (and they presumably also have extra lens coatings). The same is true of Nikon I believe. I think third party manufacturers are the only ones that made and market the category 1 type of lens (i.e. lenses designed for full frame with just a digital coating).

Yes. You're right. Thanks for that correction.

But Contriver's original question was about the Canon EF 55-200mm f/4.5-5.6, which, acording to Canon's website, "is compatible with all EOS cameras" and has "new optical coatings ... optimized for digital cameras". So I think my argument still applies within the scope of Contriver's question.

[peripatetic]

Yes, good point.

There is no engineering advantage to building "crop" lenses with a smaller image circle when it comes to telephoto lenses.

It is only the wide-angle end where it makes a difference, and since digital came along all of the manufacturers are putting the new coatings on all of their new lenses because they will mostly be used on digital cameras.