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09-10-2010, 01:13 AM   #61
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QuoteOriginally posted by falconeye Quote
AFAIK, Pentax is well aware of the resale market for FA lenses. IMHO, they won't compete with what is already available 2nd hand. And anyway, a K-5 should be paired with a FA31, shouldn't it?
Excuse me, but what FA31 really should be paired with is a god damn inexistant full-frame K-mount DSLR.

:ugh:

09-10-2010, 01:45 AM   #62
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QuoteOriginally posted by ghelary Quote
Double thinking of the reason behind an aperture of 2.4 instead of 2, I came to the following reasoning.

2.4 provides a bigger DOF than 2, that means that the system will be more tolerant to assembly issues. Given the fact that this lens is targeted to be the cheapest possible, therefore the quality checks and the quality of material and assembly are on the lower side (compared with the DA ltd) the 35/2.4 will have more likely defaults, limiting maximal aperture to 2.4 is maybe a way to minimize such faults.
Your reasoning is so flawed. Any lens being manufactured by any company of whatever maximum aperture will go through a series of QC checks. The DOF has got nothing to do with it.
This is a cheap lens targeted at the mass market at a very low price point. Everything in it's production and design is aimed at making it at a target production price.
09-10-2010, 02:19 AM   #63
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QuoteOriginally posted by creampuff Quote
Your reasoning is so flawed. Any lens being manufactured by any company of whatever maximum aperture will go through a series of QC checks. The DOF has got nothing to do with it.
This is a cheap lens targeted at the mass market at a very low price point. Everything in it's production and design is aimed at making it at a target production price.
I remember discussing with some shop keeper (LEica reseller) who was also a photographer, and he told me that after trying several faulty Voigtlander lenses he stopped retailing them. Even though Cosina make both the Zeiss and Voigtlanders, QC seems completly on another level.

I would not expect Pentax to conduct as much QC for a cheap kit lens as for a FA31ltd. Tolerances also would be on a much higher level for a kit lens. And the smaller is the DOF, the more you will see things like misaligment issues.

I don't think my reasoning is flawed on that level. And reducing the costs of acceptable QC fits in the making of a cheap lens.

Anyway, I saw in the comments on "the online photographer" another argument for a smaller max aperture. This lens is targeted to beginers, upgrading from their kit lens. You would expect them to continue shooting full auto, and in particular not paying much attention to "where" they are focusing. A little more DOF would make it more forgiving. And those users would not accuse their lens for being "soft" while in fact they where focusing on the tip of the nose instead of the eye while the lens is fully opened.
09-10-2010, 04:16 AM   #64
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QuoteOriginally posted by creampuff Quote
No doubt both the lenses you mention do show good resolution figures at maximum aperture but peak sharpness is achieved only at f/5.6 (looking at Photozone's reviews). If you look at the Nikkor AF-S DX 35mm f/1.8 G for example, at f/2.8 it already betters both lenses in terms of sharpness and achieves peak sharpness at f/4 and f/5.6 is just as good.
When did people forget to recognize you can't compare Photozone's resolution figures literally across test platforms? You need to use a calibration lens (i.e. Sigma that was tested for both platforms) and scale.

09-10-2010, 04:26 AM   #65
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QuoteOriginally posted by Kunzite Quote
I doubt we can compare manufacturing costs by a crude estimation of diameters, for lenses with different design (btw, the 35mm must be a retrofocus design, unlike a 55mm).
About the light "loss": by mounting a large format lens on my camera, how many stops would I gain? It doesn't matter what was meant for, if we'd use it on an APS-C camera.
My comment was with respect to another remark saying that digital doesn't require as much light. Which made me answer that it also doesn't get as much light for the same f-stop.

That a normal lens requires a retrofocus design is a consequence of using a 35mm mount with an APSC sensor. It's not the customers who should pay for that decision. At least not if we got no other option

QuoteOriginally posted by ilya80 Quote
Excuse me, but what FA31 really should be paired with is a god damn inexistant full-frame K-mount DSLR.

:ugh:
Yes, but I may not have said otherwise
09-10-2010, 04:31 AM - 1 Like   #66
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QuoteOriginally posted by omega leader Quote
When did people forget to recognize you can't compare Photozone's resolution figures literally across test platforms? You need to use a calibration lens (i.e. Sigma that was tested for both platforms) and scale.
You can't scale. You must input the numbers into a mathematical model which differentiates between blur due to lens softness and blur due to a finite Nyquist frequency and demosaicing/AA artifacts. An approximate mapping across platforms is then feasible but as long as no complete MTF curves are published, the mapping is not very reliable.

For the time being, the best way to compare across platforms is to note the f-stop where a lens peaks in the center/borders/corners. The f-stops carry across platforms and the lower the f-stop, the better the lens.
09-10-2010, 04:39 AM   #67
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QuoteOriginally posted by falconeye Quote
You can't scale. You must input the numbers into a mathematical model which differentiates between blur due to lens softness and blur due to a finite Nyquist frequency and demosaicing/AA artifacts. An approximate mapping across platforms is then feasible but as long as no complete MTF curves are published, the mapping is not very reliable.

For the time being, the best way to compare across platforms is to note the f-stop where a lens peaks in the center/borders/corners. The f-stops carry across platforms and the lower the f-stop, the better the lens.
I meant scale as is lens X is better on than lens Y on one body and lens Y is better than lens Z on another body, therefore lens X is better than lens Z. (X>Y>Z)
09-10-2010, 04:57 AM   #68
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QuoteOriginally posted by ghelary Quote
Double thinking of the reason behind an aperture of 2.4 instead of 2, I came to the following reasoning.

2.4 provides a bigger DOF than 2, that means that the system will be more tolerant to assembly issues. Given the fact that this lens is targeted to be the cheapest possible, therefore the quality checks and the quality of material and assembly are on the lower side (compared with the DA ltd) the 35/2.4 will have more likely defaults, limiting maximal aperture to 2.4 is maybe a way to minimize such faults.
A deeper DOF also far more tolerant of AF issues.

It's also more tolerant of colour fringing on the very thin digital focal plane, important when in-camera processing JPEG's is actually the norm, not the exception.

As for assembly, if there is a manufacturing error, it's just a lot cheaper to throw the piece in error away (recycle really) and start again. with fewer pieces, there's less assembly steps, therefore less opportunity for error. That is one reason why manufacturers designate elements and groups in their marketing.

09-10-2010, 05:20 AM   #69
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QuoteOriginally posted by falconeye Quote
You can't scale. You must input the numbers into a mathematical model which differentiates between blur due to lens softness and blur due to a finite Nyquist frequency and demosaicing/AA artifacts. An approximate mapping across platforms is then feasible but as long as no complete MTF curves are published, the mapping is not very reliable.
Of course if Pentax would get with the programme and publish their own MTF charts we would at least have a stable basis for comparison. Has there ever been a concerted attempt to lobby for this?
09-10-2010, 05:27 AM   #70
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QuoteOriginally posted by gazonk Quote
Speaking of the FA limiteds: did you notice that the K-r simulator has the FA43 as one of the lens alternatives?
Not only noticed but used as an illustration for my article Pentax K-r Due In October. Darned good marketing, I think, since the FA43 actually looks better with this style than any previous Pentax DSLR.
09-10-2010, 05:30 AM   #71
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If that were true ...

QuoteOriginally posted by falconeye Quote
My comment was with respect to another remark saying that digital doesn't require as much light. Which made me answer that it also doesn't get as much light for the same f-stop.
... the same 35mm f/2 lens set at f/2.8 would render differently exposed photographs if used on a:
  • Nikon D700, at ISO 200 and with a shutter speed of 1/125s;
  • Nikon D300, at ISO 200 and with a shutter speed of 1/125s;
  • Olympus EP-1, at ISO 200 and with a shutter speed of 1/125s.
But would it really?

Cheers,
09-10-2010, 05:51 AM   #72
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QuoteOriginally posted by ghelary Quote
FA50/1.4 and F50/1.7 share the same optical formulas.
No, they do NOT. A lot of people assume this and they are completely and totally wrong. The lineages of these two lenses are distinct. The FA50 1.7 is based upon the Super Tak 55 f/1.8 formula and the 1.4 is based upon the Super Tak 50mm f/1.4.

The F/Fa 50mm f/1.7 has Six elements in five groups. The /Fa 50mm f/1.4 has 7 elements in 6 groups. There are other differences including the number of aperture blades. For a somewhat muddled discussion of this see my post in this thread:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/62607-takumar-55-1-8-a.html

I've looked at this carefully. This is not a case of up market down market. That is why the performance is different enough that the f/1.7 has a bit of a following. I am among them.

I agree that Pentax has done crippled lenses to appeal to multiple markets and to gain some market share, but a MUCH better example of crippling lenses for market share would be the Super Tak 55 f/1.8 and 2.0. Same lens. Same exact lens except for aperture ring.

Respectfully,

woof!
09-10-2010, 05:55 AM   #73
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QuoteOriginally posted by falconeye Quote
My comment was with respect to another remark saying that digital doesn't require as much light. Which made me answer that it also doesn't get as much light for the same f-stop.
QuoteOriginally posted by slocant Quote
[If that were true]... the same 35mm f/2 lens set at f/2.8 would render differently exposed photographs if used on a:
  • Nikon D700, at ISO 200 and with a shutter speed of 1/125s;
  • Nikon D300, at ISO 200 and with a shutter speed of 1/125s;
  • Olympus EP-1, at ISO 200 and with a shutter speed of 1/125s.
But would it really?

Cheers,
... and light meters would have to take into account the size of the film or sensor in order to provide adequate exposure values.

Cheers,
09-10-2010, 06:31 AM   #74
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Maybe they did the same than with 55mm They were /1.8 and /2 but the /2 was artificialy rendered /2. It was the very same lens. Maybe they did it the same for FA35 -> DA35.
09-10-2010, 06:41 AM   #75
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QuoteOriginally posted by woof Quote
No, they do NOT. A lot of people assume this and they are completely and totally wrong. The lineages of these two lenses are distinct. The FA50 1.7 is based upon the Super Tak 55 f/1.8 formula and the 1.4 is based upon the Super Tak 50mm f/1.4.

The F/Fa 50mm f/1.7 has Six elements in five groups. The /Fa 50mm f/1.4 has 7 elements in 6 groups. There are other differences including the number of aperture blades. For a somewhat muddled discussion of this see my post in this thread:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/62607-takumar-55-1-8-a.html

I've looked at this carefully. This is not a case of up market down market. That is why the performance is different enough that the f/1.7 has a bit of a following. I am among them.

I agree that Pentax has done crippled lenses to appeal to multiple markets and to gain some market share, but a MUCH better example of crippling lenses for market share would be the Super Tak 55 f/1.8 and 2.0. Same lens. Same exact lens except for aperture ring.

Respectfully,

woof!
I pointed the different optical design in post 13 but I didn't get into the lineage to the respective Taks. https://www.pentaxforums.com/forums/1172559-post13.html
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