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04-19-2013, 09:37 AM   #121
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QuoteOriginally posted by Unsinkable II Quote
My guess is that Pentax/Ricoh (I should say Ricoh/Pentax) don't need Sigmaron in their business plan.
What does that mean? Are you suggesting that Pentax took actions to intentionally discourage or prevent Sigma and Tamron from continuing to release lenses in K-mount?

04-19-2013, 09:59 AM   #122
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I agree with Edgar... WTF? Why would they ever do that? It's not up to them anyway, as far as I know... but maybe I'm wrong. Can't Sigma make lenses for any mount they want? If they feel they can make money producing the lens for a certain mount, they will produce it, yes?

And even if what you say is true, they are wrong. They do need Sigma/Tamron. Without them the system just becomes more niche and less viable in total, IMO. Perhaps not everyone feels that way. But I bought Sigma lenses specifically because of all the issues with SDM motors, and I'm very happy with them. I own 6 lenses, and only ONE (FA 50mm 1.4) is a Pentax. The rest are Sigma, and they perform extremely well.

I would think that a 1.8 zoom such as this would be the perfect thing to release for Pentax, seeing as their top end dslr currently is DX format. But oh well, I guess.
04-19-2013, 10:10 AM   #123
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QuoteOriginally posted by zdwagner Quote
And even if what you say is true, they are wrong.
If it weren't for Sigma and Tamron, I would not own a Pentax. And if they stop supporting Pentax, then I may have to reevaluate my system of choice in the future. I have no confidence that Pentax will provide all the lenses I would ever want, and even if they did, I don't think I would like the prices based on their pricing history.
04-19-2013, 02:09 PM   #124
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QuoteOriginally posted by Unsinkable II Quote
My guess is that Pentax/Ricoh (I should say Ricoh/Pentax) don't need Sigmaron in their business plan.
You mean Sigmavoigtzeisstokinaron??

Sigma (and zeiss and voigtlander and tamron and tokina) make lenses to make money. If you go by DSLR sales, you can probably expect 1 out of 20 lenses sold to be a K-mount lens. Sigma (et al) do not think that is enough lenses to be a worthwhile investment.

04-19-2013, 02:19 PM   #125
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QuoteOriginally posted by cali92rs Quote
If you go by DSLR sales, you can probably expect 1 out of 20 lenses sold to be a K-mount lens.
To be honest, I would bet that 1 out of 20 is probably overstating Pentax sales, at least in the US. I've seen way more than 20 DSLR's out and about, but I can't say that I ever remember seeing anyone else with a Pentax DSLR. (Unless you count my brother-in-law with his lime green K-r, but he only went with Pentax because that's what I use.)
04-19-2013, 09:31 PM   #126
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QuoteOriginally posted by Edgar_in_Indy Quote
To be honest, I would bet that 1 out of 20 is probably overstating Pentax sales, at least in the US. I've seen way more than 20 DSLR's out and about, but I can't say that I ever remember seeing anyone else with a Pentax DSLR. (Unless you count my brother-in-law with his lime green K-r, but he only went with Pentax because that's what I use.)
I was at Disneyland 2 weeks ago for 3 days, and I must have seen hundreds if not thousands of DSLR but I saw not one Pentax DSLR. What I didn't appreciate was how people made fun of my Q.
04-19-2013, 09:59 PM   #127
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QuoteOriginally posted by Fontan Quote
I was at Disneyland 2 weeks ago for 3 days, and I must have seen hundreds if not thousands of DSLR but I saw not one Pentax DSLR. What I didn't appreciate was how people made fun of my Q.
There are many sheep, but few leaders!
04-19-2013, 11:02 PM   #128
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I have seen a leaked MTF chart supposedly detailing the optical performance of this lens, and I was right : this lens is going to have really bad astigmatism - field curvature will also be an issue. I from what I have seen* I predict centre sharpness will be extremely high at f/3.5 @ 18mm however, it will not be critically sharp across the frame until f/8 @ 18mm - where the DOF can mask the third order aberrations. At 35mm I predict optimal sharpness will be at f/5.6 though chromatic aberrations will be noticeable. I predict distortion will be well controlled - however the better the lens is corrected for distortion: the more problematic astigmatism and field curvature become.

* assuming a perfectly aligned lens.


Last edited by Digitalis; 04-20-2013 at 06:55 AM.
04-19-2013, 11:11 PM   #129
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Weight 810 g (1.79 lb)
Diameter 78 mm (3.07″)
Length 121 mm (4.76″)

Big lens.
04-19-2013, 11:32 PM   #130
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Gear for Image :: Sigma ART 18-35mm f1.8 DC Preview some sample shots
04-20-2013, 04:46 AM   #131
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QuoteOriginally posted by Digitalis Quote
I have seen a leaked MTF chart supposedly detailing the optical performance of this lens, and I was right : this lens is going to have really bad astigmatism - field curvature will also be an issue. I from what I have seen* I predict centre sharpness will be extremely high at f/3.5 @ 18mm however, it will not be critically sharp across the frame until f/11 @ 18mm - where the DOF can mask the third order aberrations. At 35mm I predict optimal sharpness will be at f/5.6 though chromatic aberrations will be noticeable. I predict distortion will be well controlled - however the better the lens is corrected for distortion: the more problematic astigmatism and field curvature become.

* assuming a perfectly aligned lens.
Here are the published MTF curves. A = F/1.8 - 10 and 30 lp/mm - f=18mm (left) and 35mm (right).

04-20-2013, 05:23 AM   #132
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QuoteOriginally posted by Fontan Quote
What I didn't appreciate was how people made fun of my Q.
Seriously? People actually noticed and commented on your camera?
04-20-2013, 06:29 AM   #133
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QuoteOriginally posted by i83N Quote
That looks promising! A bit annoying distortion @ 35mm, but otherwise the samples look very nice.
04-20-2013, 08:06 AM   #134
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The lens is big, heavy and f1.8 is rather nominal. It would be better to make 18-35/2.8 in compact body and sharp at all aperture till f8.
04-20-2013, 08:08 AM   #135
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QuoteOriginally posted by gazonk Quote
That looks promising! A bit annoying distortion @ 35mm, but otherwise the samples look very nice.
You can get the same nice photos with 16-45 or 18-55 at f4-f8.
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