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Tamron 15-30mm f2.8 Di VC USD coming end of this month
#1
Complex design 18 element 13 group design:

[Image: img_structure.gif]

 

MTF:

[Image: img00.gif]

[Image: img_exteriors.jpg]

http://www.tamron.jp/en/lineup/a012/
#2
 This looks like a good alternative to the Sigma 18-35 F1.8 which is probably it's competitor, I think I prefer the Tamrons focal length albeit with a slightly smaller aperture, 15mm is the end that usually counts. Looks like a double sliding lenshood, but is the bulbous front element excluding filters?

  Very nice, everybody's upping the game!

 

  Announced at $1,200, so there are not going to be falling out of corn flake packets!

Dave's clichés
#3
Quote: This looks like a good alternative to the Sigma 18-35 F1.8 which is probably it's competitor, I think I prefer the Tamrons focal length albeit with a slightly smaller aperture, 15mm is the end that usually counts. Looks like a double sliding lenshood, but is the bulbous front element excluding filters?

  Very nice, everybody's upping the game!

 

  Announced at $1,200, so there are not going to be falling out of corn flake packets!
That Sigma is an APS-C lens design (so a fast standard zoom), this Tamron is a 135 format "full frame" design (so a fast UWA zoom on FF). This new Tamron is more a competitor to the Sony A-mount 16-35mm f2.8, Sony FE 16-35mm f4, Canon EF 16-35mm f2.8 L IS USM II, Canon EF 16-35mm f4 L IS USM, Nikkor AF-S 16-35mm f4 VR, Nikkor AF-S 14-24mm f2.8, Sigma 12-24mm, Tokina 17-35mm f4, Tokina 16-28mm f2.8 and the upcoming Canon EF 11-24mm f4 L USM. 

 

The front element is indeed excluding "normal" filters (just like with the Nikkor 14-24mm, Sigma 12-24mm, upcoming Canon 11-24mm, Tokina 16-28mm).
#4
Lots of acrylic and low Tg glasses in there.  I bet the correction of polychromatic aberrations will be interesting.

#5
I highly doubt there is any acryl plastics instead of glass in that lens.

#6
Quote:That Sigma is an APS-C lens design (so a fast standard zoom), this Tamron is a 135 format "full frame" design (so a fast UWA zoom on FF). This new Tamron is more a competitor to the Sony A-mount 16-35mm f2.8, Sony FE 16-35mm f4, Canon EF 16-35mm f2.8 L IS USM II, Canon EF 16-35mm f4 L IS USM, Nikkor AF-S 16-35mm f4 VR, Nikkor AF-S 14-24mm f2.8, Sigma 12-24mm, Tokina 17-35mm f4, Tokina 16-28mm f2.8 and the upcoming Canon EF 11-24mm f4 L USM. 

 

The front element is indeed excluding "normal" filters (just like with the Nikkor 14-24mm, Sigma 12-24mm, upcoming Canon 11-24mm, Tokina 16-28mm).
Yes, your right! I forgot about the FF aspect, however I see it finding it's way onto a lot of APSc bodies just because of it's 2.8 aperture.

 

We'll have to see how it performs! 
Dave's clichés
#7
Quote:I highly doubt there is any acryl plastics instead of glass in that lens.
Why is that?  There's nothing wrong with acrylic - the second best corrected category of lenses (phone lenses) are largely acrylic.  Acrylic has a refractive index similar to K10 or NFK15.  It has stronger dispersion but it becomes gelatinous (Tg = temperature of 'gelatination') at a low temperature and is the material of choice for most "hybrid" and "molded" aspheric lenses.  There are few low Tg glasses available and they are expensive (80-100x the price of BK7).

 

Here's Ohara's current calendar - notice that there are over 100 normal glasses and 16 low Tg glasses.  This is after Ohara has discontinued 40% of its normal glass catalog to meet environmental regulations in the last 5 years.  I can give you Schott's catalog as well but low Tg glasses are not nicely separated in theirs - there are about 17 covering a similar range as Ohara's.  PK52A is an extremely nice glass that has low Tg and very minimal dispersion and only 13x BK7 cost, but it has poor stain and poor abrasion meaning you can mold it easily but the mold must be extremely precise as it is very difficult to change the surface through grinding or traditional polishing methods.

 

The common myths of "glass lenses are superior" - especially ones with 'nice, german glass' (i.e schott) are old photographers' myths.  Certainly any lens made mostly of acrylic would be extremely difficult to correct for polychromatic aberrations but it is a fairly nice material to work with and is in no way inferior.  There are many glasses which are much worse than Acrylic.  People may also be surprised if they learned that lots of the national associations for glasses are 'invalid'... both Schott (DE) and Ohara (JP) produce extremely large volumes of optical glass in the US.

 

There could be acrylic in a phone lens, or a photographic lens, or a $10M one of one large optic, or a $50k cinema lens, or any other application - it's not bad.  The f/0.48 lens we have in the lab I work in contains an acrylic element and it is a far more impressive specimen than most any photographic lens.

#8
Quote:Why is that?  There's nothing wrong with acrylic -

 

[...]

 

There could be acrylic in a phone lens, or a photographic lens, or a $10M one of one large optic, or a $50k cinema lens, or any other application - it's not bad.  The f/0.48 lens we have in the lab I work in contains an acrylic element and it is a far more impressive specimen than most any photographic lens.
 

I don't think I've ever had glass eyeglasses.   Some of my plastic lenses have been decent, some have been excellent.  In the end, every photographic image I've created or viewed has had to go through plastic lenses (on my face) at some point.   B) 


But maybe I should change to glass eyeglasses? I really don't know.

 

http://www.zeiss.com/vision-care/en_de/b...enses.html

 

http://www.zeiss.com/vision-care/en_us/b...tml#step-2
#9
Hi Scythels,

                   I do my best to understand and take on board your threads, but the acronyms used go beyond my very basic optical knowledge, perhaps a little "acronym key" at the bottom of the page would put me and maybe other "non opticians" better on track. I know it doesn't apply so much to your last post.

 

 

Thanks!

Dave's clichés
#10
Dave,

 

sometime in the near future (after synoptsys approves my student license for Code V and I don't have to travel to the lab to generate figures and the like - it's been 16 days of waiting so far...) I'll make a glossary post/series of sorts.  It will take time to put together and I have many deadlines in the next two weeks before the director of my lab leaves on a business trip.  There will be many elements to such a post and I would much rather do it right than do it hastily.

  


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