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08-02-2015, 11:16 AM   #16
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QuoteOriginally posted by pathdoc Quote
We're talking about the macro here, yes? You're probably right, but for the sort of work a macro lens is designed (or perhaps "optimised" is a better word) to do, that's a strength. It's a scientist's instrument rather than an artist's.
I was talking about the DA 35 2.4, the plastic wonder... but, I love the way my 70 macro renders to the point it's probably my favourite portrait lens. But like every Sigma these days, it's really heavy. Correction and sharpness together comes at a price in weight.

08-02-2015, 11:20 AM   #17
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Ah. Given the thread title, I figured the macro 35 was a fair call. I stand corrected.
08-02-2015, 12:20 PM   #18
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QuoteOriginally posted by lytrytyr Quote
While the FA Limited primes are all f/1.8 or f/1.9,
one interesting feature of the DA Limited primes is how the maximum aperture steadily decreases as they get wider.
The short tele, DA 70, is f/2.4, the normal DA 40 and DA 35 Macro are f/2.8, the wide DA 21 is f/3.2, and the more extreme wide DA 15 is f/4.
This makes very good photographic sense in terms of the slowest shutter speed to avoid camera shake.
If you fix that at 1/f seconds for the focal length f in mm, all the lenses are right for around EV 8 wide open.
A bit obscure (?) but interesting observation which highlights a parameter that might be acting in the design of the lineup.

For those discussing the size and build quality. These are obviously limited trademarks which are well known. It's the other things and which I find more interesting.

My point with the description of the 21mm was that as far as I'm concerned the relatively slow speed of the lens is a non issue for the type of photography I use it for (and it's designed for?) The two use cases of 1) landscape/street/group shots which require large DOF 2) and wide angle closeups of objects are well catered for.

The f2.4 of the 70mm is in my usage also fast enough for head/torso portraits. Faster and the DOF tends to become to shallow? Often even f2.4 is to fast and bits of the face become to blurry. For full body portraits a faster lens might be useful for better subject separation though.

As far as i know the 70mm is quite sharp across the frame which it might actually not have to be. Perhaps there is a second use case with the 70mm where this becomes important. Anyone has a favourite type of photo with the 70 that requires across the frame sharpness?

I dont' own the 40mm as I have the 35mm plastic fantastic and I don't want to give in to LBA (for philosophical rather than financial reasons.) This one has a less clear raison d'être to me as it would be useful to have this one fast? Obviously it's absolutetly tiny instead. Anyone got ideas for the usecase and design parameters of this one?

Looking at the tiny size and visual design of the lenses you could guess that Pentax has been going after mobile and discreet photographers. Perhaps with a bit of nostalgia for old street/rangefinder photography considering the visual design and build of the lens. The custom hoods are a real sign of this emphasis imho. The decision to allow distortion of the 21mm would be explained by this. As it's only really for architectural photography the pincusion distortion is a problem, and us architecture nerds should be using large format anyway

Perhaps someone can argue against my claim that super fast lenses are a bit redundant for the above scenarios? I'd also like to hear more about how people see the limitations of the limiteds and how (if) it affects their photography negatively.
08-02-2015, 01:18 PM   #19
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I think the 40 Limited needs the f/2.8 to do a nice job with short range portraits...

Cross posted again guys sorry but so many people think this lens can't do what it can do...


08-02-2015, 01:49 PM   #20
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QuoteOriginally posted by UncleVanya Quote
I think the 40 Limited needs the f/2.8 to do a nice job with short range portraits...

Cross posted again guys sorry but so many people think this lens can't do what it can do...
Yes my point was that perhaps it should be a bit faster. By maybe I'm wrong as for portraits you'd need to go closer than the 70 which means shorter DOF. My thinking was that it should be faster when you want subject isolation but with context around say a couple on a busy street or something. But in cases like that you don't want a super creamy slush around them. The context needs to be legible.

Hmm it looks like I have to ditch my principles and get the lens to figure out it's presonality

I do like the look of normal lenses. Best field of view as it helps avoid mannered looking images. Find it hard to use though.
08-02-2015, 06:14 PM   #21
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QuoteOriginally posted by house Quote
Hmm it looks like I have to ditch my principles and get the lens to figure out it's presonality
This is the basis of LBA...... the next stage depends upon whether you have the personality traits of a hoader or not...... simple as really!

If you sell a lens, then later buy an identicle one, your still a hoarder, you just haven't come to terms with it yet.
08-03-2015, 12:57 AM   #22
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QuoteOriginally posted by house Quote
Anyone has a favourite type of photo with the 70 that requires across the frame sharpness?
I use the 70mm for landscapes more often than I use the DA 15mm, but that might just be me...

08-03-2015, 07:52 AM - 1 Like   #23
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QuoteOriginally posted by clockworkrat Quote
What do you mean by rendering?
Isn't that the process that turns horses into glue?
08-03-2015, 09:53 AM   #24
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QuoteOriginally posted by lytrytyr Quote
Isn't that the process that turns horses into glue?
08-03-2015, 11:02 AM   #25
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DA Limited primes: Evidence for paternity suits

DA 70/2.4:



SMC 67 105/2.4:



++++++++++++++++++++++++++++++++++++++++++++++++++

DA 40/2.8:



M 40/2.8:



++++++++++++++++++++++++++++++++++++++++++++++++++

DA 21/3.2:



M 20/4:




Acknowledgements to Bojidar Dimitrov (K-mount diagrams); @gofour3 and Xitek (SMC 67 diagram).
08-04-2015, 01:09 PM   #26
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I think some read to much into the goal of the lenses.

For sure ltd are intented to be small, light and with metal contruction. They tend so to have slow apperture quite high resistance to flare. Maybe the second part is just a consequence or maybe it was a requirement. But for sure, slow apperture was a trade-off, not an objective.

For the sharpness/max apperture compromize in general it is quite simple. Due to the registration distance of the K-mount making a small 28, 35, 40, 50 or 70mm is quite easy... Even with somewhat fast apperture. But doing a fast and sharp wide angle is much more challenging.

And so the DA70 and DA35 are the 2 sharpest lenses of the DA ltd while DA21 and DA15 are the softest. Still sharpness is more important for landscapes than for portraitures. And also the DA15 and DA21 have more distorsion than the DA35 or DA70... Even through DA15 or DA21 would be used a lot for architecture where distorsion is a real issue.

So what?

It happen that it is quite easy to design a quite fast 70mm that is sharp from corner to corners and fast. That what the DA70, and in a very small pakage. That make it also a great landscape lense (due to the corners to corners sharpness). But while the designer of the lenses did interresting compromize, we should not look too far why the DA21 is quite slow and why it is not that sharp.

The designers wanted a serie of pancakes and another series of bigger but still quite small lenses. They got the 21, 40 and 70 on one side and the 15 and 35 on the other side.

Honestly would I had the choice, I would have prefered the DA21 to be the size of the DA15 or DA35 and to get the DA35 or DA70 sharpness on it. But that's just me.
08-04-2015, 01:58 PM   #27
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Given that the DA 70 is the same size as the DA 15 I'm not sure why the 15 and 35 are grouped in one set and the 21, 40, and 70 in the other. The 21 and 40 are pancake lenses - the 70 and 15 are not. Also as you move away from 45mm in either direction the lenses must get larger due to the way the registration distance impact things. The 15 is fighting that as is the 70 even the 21 fights it.

This focus on small lenses is fairly common - even the Zeiss designers have commented on their approach and how the primes they make are not sharper and faster than some of their zooms but they are less complex and easier to carry.
08-04-2015, 05:27 PM   #28
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QuoteOriginally posted by UncleVanya Quote
Given that the DA 70 is the same size as the DA 15 I'm not sure why the 15 and 35 are grouped in one set and the 21, 40, and 70 in the other. The 21 and 40 are pancake lenses - the 70 and 15 are not.
The DA 21 is 25mm long. The DA 70 is 26mm.
(According to Pentax DA Prime Lenses - Reviews and Specifications - SLR and Interchangeable Lenses - Pentax Lens Reviews & Lens Database)

Unless you're setting a very strict one-inch (25.4 mm) limit on pancakes,
I don't see why the DA 70 shouldn't qualify.
08-04-2015, 05:40 PM   #29
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QuoteOriginally posted by lytrytyr Quote
The DA 21 is 25mm long. The DA 70 is 26mm.
(According to Pentax DA Prime Lenses - Reviews and Specifications - SLR and Interchangeable Lenses - Pentax Lens Reviews & Lens Database)

Unless you're setting a very strict one-inch (25.4 mm) limit on pancakes,
I don't see why the DA 70 shouldn't qualify.

DOH - because I was using the length with the HOOD! In carrying mode the DA 15 and the DA 70 (with hood) are approximately the same size. I own both and the DA 40 Limited. I forgot the hood is pretty big on the DA 70 even collapsed. LOL. Thanks for pointing that out.
08-04-2015, 06:40 PM   #30
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QuoteOriginally posted by UncleVanya Quote
DOH - because I was using the length with the HOOD! In carrying mode the DA 15 and the DA 70 (with hood) are approximately the same size. I forgot the hood is pretty big on the DA 70 even collapsed.
Yes, I always leave the hood attached on mine, and if it's wrapped in cloth in my bag,
I can barely tell it from the wrapped-up DA 15 when I'm reaching for it.
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