[Blacknight659]

What a poor choice of words for a thread title. I mean, seriously?

This thread shows a lack of understanding of physics and optics in the original post.

You might as well ask why Mercedes doesn't make a luxury car that is very spacious inside and fits 8 people, and still is the size of a subcompact on the outside. What is foolish is the question, not the fact that those things don't exist.

Ouch... You sir the definition of an internet troll. I recognize this lens is most likely impossible to build but keep the hating to yourself.

[AquaDome]

While I know the 20-40mm limited is already here, I would prefer if this lens were a bit wider and/or a bit more zoomed. Does anyone share my feelings on this?

If I could design and produce my own lens, I would build something with four main features in mind. This lens would be a wide zoom, bright at f2.8, compact, and weather sealed. As these features are a necessity, I would be willing to compromise on the zoom range and the constant aperture as long as it didn’t go any darker than f4. Maybe it would be a 15-35 or 18-45.

Do you want it to cover full-frame as well?

An equivalent lens could be manufactured, but the sensor behind it would have to be tiny. You're already lucky the 20-40 is APS-C sized and not full-frame.
Carry around a 645 with the FA 45-85 for a day and maybe you'll appreciate the DA20-40 Limited for what it is instead of calling it an abomination for what it isn't.

[Blacknight659]

Do you want it to cover full-frame as well?

An equivalent lens could be manufactured, but the sensor behind it would have to be tiny. You're already lucky the 20-40 is APS-C sized and not full-frame.
Carry around a 645 with the FA 45-85 for a day and maybe you'll appreciate the DA20-40 Limited for what it is instead of calling it an abomination for what it isn't.

I can see where it would seem I was calling the 20-40 an abomination. I was trying to my lens would be the abomination. I actually like the 20-40 but would rather have a wider / longer lens that is also bright. However, it is probably impossible to create this lens and still stay compact.

[VisualDarkness]

Ouch... You sir the definition of an internet troll. I recognize this lens is most likely impossible to build but keep the hating to yourself.

Actually his comparison is pretty much spot on. An optical lens design is a result of a mastery of compromises with the material and tools available. You can't brake the laws of physics, you can only utilize them with the tools and materials available and find the optimal compromise for what you want to achieve.

I also don't get why you named it "abomination", that looks like an attempt to create hostile reactions when reading through the post.

[tvdtvdtvd]

Can I just have an eagle eye installed in my camera? You know, an actual eagle eye? How hard would that
be? The engineers just have to >want< to do it and I'm sure they could make it happen.

[boriscleto]

This lens with the same focal length is nothing new for Pentax. I think there was an SMC all manual 20-40 model which was manufactured and sold starting in the 1980's. Also a FA 20-35 f4 starting in 1998.

The M series had a 24-35/3.5 and a 24-50/4. There was a 40-80/2.8-4...

[bdery]

The 16-50 has been around a long time. There are probably engineers outside of Hogwarts who could update it to be more svelt.

Being an optical designer myself, I can attest that we do try to get it right the first time... Incremental improvements are likely, but not ervolutions.

The Tamron 17-50/2.8 is between the 16-50 and the 20-40 in size.

Much nearer the 16-50. Keep in mind that the 16-50 is 6% wider than the Tamron. Both actually dwarf the 20-40.

Ouch... You sir the definition of an internet troll. I recognize this lens is most likely impossible to build but keep the hating to yourself.

That is not the definition of a troll, nor have I seen hate. Strong disagreement, surely, but nothing more.

[Blacknight659]

Actually his comparison is pretty much spot on. An optical lens design is a result of a mastery of compromises with the material and tools available. You can't brake the laws of physics, you can only utilize them with the tools and materials available and find the optimal compromise for what you want to achieve.

I also don't get why you named it "abomination", that looks like an attempt to create hostile reactions when reading through the post.

I see your point about the title, while this is not the reaction or attention I was going for, I can see where this solicited a poor response. I will attempt to change it. As for the creation of the "dream lens" I can see from the posts it may never be due to physical limitations. Thank you all for honest feedback and sorry for misleading the thread.

---------- Post added 12-16-14 at 03:18 PM ----------

NOTE: This thread was an attempt to start a discussion about a lens I would create however impossible that may be. I understand the title of this thread was misleading to many of you. I was trying to describe my dream lens and how awesome it would be if it could be created. It seems many readers assumed I was attempting to attack logic or put down the current lens line up. This is not the case. I see how this was misleading and apologize. I do appreciate some of the positive conversation in this thread! Also, I am happy to know this could draw the attention that it did. Thank you all for your comments and please consider my update to this post.


While I know the 20-40mm limited is already here, I would prefer if this lens were a bit wider and/or a bit more zoomed. Does anyone share my feelings on this?

If I could design and produce my own lens, I would build something with four main features in mind. This lens would be a wide zoom, bright at f2.8, compact, and weather sealed. As these features are a necessity, I would be willing to compromise on the zoom range and the constant aperture as long as it didn’t go any darker than f4. Maybe it would be a 15-35 or 18-45.

Hopefully this clears things up!

[GeneV]

Being an optical designer myself, I can attest that we do try to get it right the first time... Incremental improvements are likely, but not ervolutions.



Much nearer the 16-50. Keep in mind that the 16-50 is 6% wider than the Tamron. Both actually dwarf the 20-40.

I try to get things right the first time, too, but I do find I do some things better now than 8 years ago.
I see a lot of photographic equipment now that makes 2007 look old. I'm not using my K10d much lately.

The sizes of the lenses I mentioned (and the basis for my previous post) are:

DA* 16-50-- 3.3 x 3.9"
Tamron 17-50--2.9 x 3.2"
DA 20-40--2.80 x 2.72"

It looks to me like the Tamron is closer to the DA 20-40 than the 16-50, but I have never held them in my hands.

[Na Horuk]

The Tamron is compact and light, but it is not on the same build level, and it is not WR. The DA 20-40mm has a beautiful barrel, zoom ring and so on. Its lens cap is a bit odd, though

[GeneV]

The Tamron is compact and light, but it is not on the same build level, and it is not WR. The DA 20-40mm has a beautiful barrel, zoom ring and so on. Its lens cap is a bit odd, though

I'm not really saying that I would like one or the other, but just that the size is closer to the 20-40 than the 16-50.

[JinDesu]

I'm not really saying that I would like one or the other, but just that the size is closer to the 20-40 than the 16-50.

It's possibly the lack of in-lens motor that saves the size on the Tamron versus the other two. This can be seen in the Sigma version (3.3" x 3.6").

[GaryH]

I'm not really saying that I would like one or the other, but just that the size is closer to the 20-40 than the 16-50.

Weight wise the
16-50 565 grams
17-50 430 grams
20-40 283 grams

[GeneV]

It's possibly the lack of in-lens motor that saves the size on the Tamron versus the other two. This can be seen in the Sigma version (3.3" x 3.6").

Maybe, but we really don't know. The Sigma may also be sized for optical stabilization it includes in other mounts. When Tamron added optical stabilization, the size went from 2.9 x 3.2 to 3.13 x 3.7, but the model with a built in motor and no OSS stayed the same at 2.9 x 3.2. There may also be other reasons for size changes in both cases.

---------- Post added 12-16-14 at 08:45 PM ----------

Weight wise the
16-50 565 grams
17-50 430 grams
20-40 283 grams

Still, the Tamron is pretty close the middle, as I indicated in my original post. It is 135 grams less than the 16-50 and 147 grams more than the 20-40,