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03-26-2007, 11:44 PM   #1
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I was right! Interesting fact Re DA70/2.4

When Cosina decided to discontinue the best selling lens of it's entire "SL" line of lenses for SLRs, I was disappointed (and a bit confused). A couple (probably three) of months after Cosina's discontinuing of the Voigtlander 75mm f/2.5 SL, Pentax announced a new Limited, the DA70mm f/2.4, disappointment turned to suspicion that maybe Pentax had licensed the earlier discontinued Voigtlander 75mm design; the FL and apertures of the lenses are both fairly close (2.4 vs 2.5 is almost nothing) too. At that point I couldn't get my hands on an image of the new DA70's lens formula, so I waited for Bojidar Dimitrov to update his site, which he did, and here's what I got:



Seems as though my thinking was right. Pentax seems to have "flattened" the design a bit, but otherwise they look identical.

So now we have a Voigtlander SL lens with SMC coating and Limited metal jacket. Strange and interesting beast, the V75 I have has some great properties and can compete with the 77 save for aperture and skin tone.

If Pentax drops the price a bit, I'd be interested, only $100 or so less than a 77 doesn't make it too attractive for me, especially when the 77 can still be found brand new.

What do you folks think.

Cheers!
-Asad

Images of lens formulas come from the Cosina website and Bojidar Dimitrov's K-mount page, and are owned by whoever holds their respective copyrights.


Last edited by Asad_Masede; 03-26-2007 at 11:52 PM. Reason: Forgot to add credits and disclaimer at the end.
03-27-2007, 03:57 AM   #2
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Very interesting find Asad. I've seen quite a few shots from you with the Voigtlander, and was very impressed with image quality and Bokeh.
Like you...unless the DA70 drops in price..I don't really have an interest in it....because I have the 77.
If I didn't have it, and it was no longer available..I would get the DA70 in a heartbeat.

But if people want a great Prime that is half the height & weight of the 77....snap one up.
Cheers.
03-27-2007, 01:22 PM   #3
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Scott, yeah, $350-$400 USD level would be great for the 70mm, and like you said having the Voigtlander formula isn't a bad thing at all, in fact all those SL lenses are extremely high quality. Higher than the credit many give the lenses, having the "Cosina" name attached to it and what not.

Now, Pentax, please reduce the cost of the lens and stop selling the DA70 higher priced initially, pretending that lens development cost an arm and a leg.

The V75/2.5, with all it's heavy duty metal construction and fine finish (tougher built than the Limiteds) used to sell for approx $285, $150 more for the bells and whistles the DA70 has over the V75? Almost $500, AFTER rebate, is simply unacceptable to me.

Cheers,
-Asad

QuoteOriginally posted by Scott Rylance Quote
Very interesting find Asad. I've seen quite a few shots from you with the Voigtlander, and was very impressed with image quality and Bokeh.
Like you...unless the DA70 drops in price..I don't really have an interest in it....because I have the 77.
If I didn't have it, and it was no longer available..I would get the DA70 in a heartbeat.

But if people want a great Prime that is half the height & weight of the 77....snap one up.
Cheers.
03-27-2007, 05:51 PM   #4
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Thanks for posting this optical formula here. That is really helpful. Always delightful to see designs even I knew nothing about it.

I do wonder: If the optical arrangement of Da seems shortened comparing to Cosina, wouldn't this change the optics altogether and making this more expensive to do?

I do envy the compact size of Da 70 without the hood

03-29-2007, 12:44 AM   #5
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QuoteOriginally posted by roentarre Quote
Thanks for posting this optical formula here. That is really helpful. Always delightful to see designs even I knew nothing about it.

I do wonder: If the optical arrangement of Da seems shortened comparing to Cosina, wouldn't this change the optics altogether and making this more expensive to do?

I do envy the compact size of Da 70 without the hood
I suppose you could say that Pentax "flattened" the design a bit, other than being 5mm short on the FL, I don't think that changed the characteristics of the design too much, from what I've seen of the DA70 images, they're simply great and have similar bokeh and rendering to that of the V75/2.5.

Cheers!
-Asad
03-29-2007, 02:39 AM   #6
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And you call yourselves Pentaxians! What shameful excuses for not celebrating your LBA urges.

I have the DA70 and it is a simply remarkable little lens. I keep thinking I should get a FA77, but I have a friend with one and other than the one stop difference I can't tell them apart.

I can give you one more huge reason to get the DA70 -- Quick shift focus. And another -- $50 rebate. (But you'll have to fight a little on that one -- the rebate form lists the wrong UPC code and the fulfillment company won't honor it without a fight.)
03-29-2007, 02:58 AM   #7
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QuoteOriginally posted by jbarnhart Quote
And you call yourselves Pentaxians! What shameful excuses for not celebrating your LBA urges.

I have the DA70 and it is a simply remarkable little lens. I keep thinking I should get a FA77, but I have a friend with one and other than the one stop difference I can't tell them apart.

I can give you one more huge reason to get the DA70 -- Quick shift focus. And another -- $50 rebate. (But you'll have to fight a little on that one -- the rebate form lists the wrong UPC code and the fulfillment company won't honor it without a fight.)
LoL

Well you're right, but it's not a huge urge when I already have two lenses around the same FL (one with almost identical formula) which puts it on the "backburner." I have a DA*16-50/2.8 to get, then a 50-135 sometime later, with Limited money.

I do want it, though, and take comfort in the fact that it shares formula with my proven V75. Also want all the other pancakes! (who doesn't?)

Cheers!
-Asad

Last edited by Asad_Masede; 03-29-2007 at 03:10 AM.
03-29-2007, 07:50 AM   #8
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[/QUOTE]I can give you one more huge reason to get the DA70 -- Quick shift focus. And another -- $50 rebate. (But you'll have to fight a little on that one -- the rebate form lists the wrong UPC code and the fulfillment company won't honor it without a fight.)[/QUOTE]

If you run up against a road block with the rebate company....promptly call PentaxUSA customer service and they will remedy the situation for you and you can rest assured that the matter will be taken care of. I know becasue I have done this with 3 out of 4 rebates. Pentax wants their customers to be happy.

Stephen

05-09-2010, 11:23 AM   #9
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Voigtlander color-heliar 75 f2.5

The SL version of this lens is the same optical formula as the rangefinder version - which has been around for years - indeed I bought my 75 SL well before the DA70 came out.

So the notion that the Heliar is a formula licensed from Pentax makes no sense - Pentax had never made a lens like it before the Heliar came out.
05-09-2010, 12:14 PM   #10
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QuoteOriginally posted by pakhead Quote
The SL version of this lens is the same optical formula as the rangefinder version - which has been around for years - indeed I bought my 75 SL well before the DA70 came out.

So the notion that the Heliar is a formula licensed from Pentax makes no sense - Pentax had never made a lens like it before the Heliar came out.
Well this is an old thread but I agree with your point.
The optical formula is not anything particularly groundbreaking. Even the M/A/F/FA 50mm f/1.7 and the K 55mm f/1.8 or f/2 have a pretty similar optical arrangement.
To say the DA 70mm is somehow linked to Cosina's 75mm Heliar is stretching the argument.
05-10-2010, 05:22 AM   #11
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Wow, you've just discovered... nothing...

With all due respect, reusing proven designs is what lens design is all about (and optical designer is my job title...)

You can purchase, for the right price, many lens designs databases each countaning thousands of designs.

And when you start designing a new lens, you ALWAYS start with an existing design. A proven design. THEN you tweak it according to your needs, requirements, and skills. That's just how it is.

If you want to see it differently, ask yourself how many ways must there be to make a 70-ish lens that works? compare the lens sizes of, say, all the 135 mm f2.8 lenses ever made. They will all be about the same size. And have the same kinds of designs.

Nothing surprising here. Move along
05-10-2010, 06:28 AM   #12
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" DA 70mm is somehow linked to Cosina's 75mm Heliar is stretching the argument."

I wouldn't be surprised if there was a link, the heliar design is very old and well regarded, and provides excellent correction for astigmatism and axial aberrations. I think that a connection existing between them would be more probable than the similarities in design being a huge coincidence.
05-10-2010, 03:20 PM   #13
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Now if they would liscence the 180mm /4, that would be something I could get behind.
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