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02-27-2009, 06:58 AM   #136
RaduA
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QuoteOriginally posted by blende8 Quote
No metal.
It's like the DA* Zooms, not like the DA* teles.
IŽonly checked the outer barrel, perhaps there is some metal within.

Regarding speed, Radu, no, I didn't do any measurements in brighter light.
The motor speed is the same, of course, but there is not so much oscillating at the end.
So, Wieland, in the measured conditions (poor light) you obtained between 1.5 and 3s and in better light you saw a faster performance? I asked because if the AF speed is better in good light then the motor is powerful enough and the problem lies elsewhere.

Thank you and regards,
Radu

02-27-2009, 07:00 AM   #137
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QuoteOriginally posted by mer Quote
Many in this thread said tha the LoCA ( or Bokeh CA ) of this lens is normal and it can't get any much better. [...] Probably the super low dispersion elements pentax used are crap.
Hi mer,

I like your term "Bokeh CA" but it is different from "Longitudinal CA" (cf. post #64 in this thread). Technically, it actually isn't even CA at all. blende8 called it FadS.

blende8 did a good test in his OP. He captured the "circle of confusion CoC in the background" and you will be able to see that this circle has a green border (and consequently slightly magenta inner part). I.e., the green CoC is a little bit larger than the red/blue CoC. You could even measure by how many percent.

So, what you call "Bokeh CA" is easily measurable and quantifiable and the measure has nothing to do with the measurements of CA you find in the tests (CA only measures if the CoC collapses to a color-independent size (LoCA) and color-independent position (LaCA) in the focus plane where ideally, it should collapse to a single, white point).


Now my question:

If you say that f/1.4 lenses with less "Bokeh CA" exist: what are the respective measures? Do you have sample images to back up your claim at least? Show them, please.

As otherwise, I think "Bokeh CA" is a phenomenon which is pretty much universal as long as the same types of glass are used (and the design isn't SuperAPO or telecentric). And why should Hoya be short in supply of good glass?


UPDATE:
I just found this nice website where you can play around with different CoC shapes and sizes (f-stops). You see the immediate change of bokeh. Black and white only.
http://www.flarg.com/bokeh.html

Last edited by falconeye; 02-27-2009 at 07:43 AM.
02-27-2009, 07:18 AM   #138
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QuoteOriginally posted by TKH Quote
Yes, you are right. The topcor is (as also the Nokton) a fantastic MF lens.

But IŽm still waiting for an answere on my question for an AF-lens from 50mm to 85mm without PF @1.4?!

Look at this.
A pic from the (Adorma at 1.300 $ priced) Carl Zeiss Planar T* 85mm F1.4 @f4:



Is it a shame that Pentax can only do a little better PF job for $730 than Carl Zeiss for $1300?!


Rainer
Haha yeah..

it is too much fokus on perfection here...comeon!

If the AF is slow, go manual fokus. Is the 1,4 is soft. Step down a step.

For god sake, we are photographers and we have smal problems all day in our work. Our job is not to take photos. it's to solve problems to get better photos.

So what are we cry about? Solve the problem insteed.
DA*55 is a great lens

Best Regards Emil
02-27-2009, 07:47 AM   #139
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QuoteOriginally posted by RaduA Quote
1) Do you have the lens?
2) Are you concern about how much a pint of beer costs in China or at your local pub? I say that because you can buy probably 10 times more beer in another country but I don't think you can go there after work daily and actually do so. And neither this virtually huge amount of beer will do anything at all for your thirst. The prices in Europe are close to twice as much for the DA* compared to FA50 so I would weep less for our American friends and be glad for myself and thankful to Pentax Europe for doing a finer job. I say that because you have UK in profile so your outrage is only theoretical by no means you must pay 3-4 times the price of FA50. Even better you are totally free to pay zero and don't get the lens! Sounds like a reasonable idea?
3) Feast your eyes with this beautiful tomato soup:

Oh, yes, Sir, it's the 1450 Euro Canon 50/1.2 (with it's blazing fast USM, btw) at f2.2. Enjoy it and think twice about bashing the DA*55 for not being perfect from wide open!

Radu
1) No I don't own it but I have used it.

2) Your analogy is not very good but I get your point. I said in some countries you have to pay twice or triple sometimes ( don't put words in my mouth by saying 4 times ) . In UK the FA50 goes for 160pounds , while the DA*55 goes for 380, this is 2.3 times. If you know cheaper sources then please by all means let me know.

3) I have used the 50/1.2 canon and I know how it performs but do you understand to design a *50* f1.2 lens instead of *55* f/1.4 is MUCH more difficult and you have to make compromises to the design ? Probably not, because if you knew that, you wouldn't show me this example.

02-27-2009, 07:58 AM   #140
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QuoteOriginally posted by ogl Quote
FA*85/1.4 was 1100-1200 USD.
About USD800 if you mean NYC price when it was still available new.
02-27-2009, 08:15 AM   #141
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QuoteOriginally posted by RaduA Quote
3) Feast your eyes with this beautiful tomato soup:
Ha ha ha ha... tomato soup!!

That was a good one...
02-27-2009, 08:28 AM   #142
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QuoteOriginally posted by mer Quote

3) I have used the 50/1.2 canon and I know how it performs but do you understand to design a *50* f1.2 lens instead of *55* f/1.4 is MUCH more difficult and you have to make compromises to the design ? Probably not, because if you knew that, you wouldn't show me this example.
Not to butt in to your conversation but isn't that why the Canon costs such a huge amount of money? Its not exactly a budget lens. And at f/2.2 its stopped down so even if its technically harder to design a 50mm f/1.2 it should still be great at 1440 euros and f/2.2?

I don't really know the Canon lens all that well. I am just questioning whether its fair for people to criticise the DA*55 for fringing.
02-27-2009, 09:45 AM   #143
RaduA
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QuoteOriginally posted by mer Quote
1) No I don't own it but I have used it.

2) Your analogy is not very good but I get your point. I said in some countries you have to pay twice or triple sometimes ( don't put words in my mouth by saying 4 times ) . In UK the FA50 goes for 160pounds , while the DA*55 goes for 380, this is 2.3 times. If you know cheaper sources then please by all means let me know.

3) I have used the 50/1.2 canon and I know how it performs but do you understand to design a *50* f1.2 lens instead of *55* f/1.4 is MUCH more difficult and you have to make compromises to the design ? Probably not, because if you knew that, you wouldn't show me this example.
Your logic is all over the place: at the same time you ask from a half (or a third?) the price Pentax full performance from wide open but give Canon an almost 2 stop "pass" because it's a "more ambitious design". And all because of the numbers on the barrel or the label on the lens and camera? Try to understand that I don't ask you to compare the DA* @ f1.4 to Canon @ f1.2. I am asking what happens @f2.2 with DA*55 for example where I already showed you how Canon acts?

Radu

P.S. I just loved the way you belittled me you seem like a perfect example of ignorance and arrogance combined.

02-27-2009, 10:04 AM   #144
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Original Poster
Stop it, please!
02-27-2009, 10:07 AM   #145
mer
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Caat :

The canon even if it's stopped down to f/2.2 it still has the same design optical flaws.

RaduA:

You do understand that most fast lenses are worse lenses than slower lenses and that fast lenses have worse performance than slower lenses even when stopped down, right? Just because they are more expensive doesn't mean the performance will be better when stopped down to f/4 for example. This is true to all lenses. Take noctilux for example , it costs 5000 but it performs worse than 20-50usd lenses at F/4. You have to make compromises in the design ( yes even with a 5000gbp lens ) to produce a fast lens. Faster glass will always have more abberations than a slower glass.

falconeye:

I , partly , agree with what you say about the term. I don't agree with you that is technically not CA though.

I hardly do "scientific" tests but I can spot how much LoCA or "Bokeh CA", more or less, one lens has when I test it but there are reviews here and there that show LoCA , such as photozone. When I do test though , I test using a ruler-like thing to test for LoCA.

I don't know about the FA50, I don't have it and have never tested it, but my SMC-M, the voigt 58mm, the zeiss 50/1.4 and the sigma 50/1.4 would NEVER show so much "bokeh CA" . Trust me on this one. In fact I have never seen so bad "bokeh CA". And although you can test for LoCA using the blende8 method in real world high contrast situations its a different story and the result differs , thats why blende8's test shows that both the FA50 and the DA*55 have more or less the same LoCA but the real world examples we see from both lenses , show the DA*55 have more "bokeh CA" , at least to my eyes.






And we can easily see the DA*55's LoCA ( showing in the focal plane, showing as purple fringing ) vs the FA*50 which has better corrected bokeh CA, which ultimately means the *special low* dispersion elements are either of bad quality or have not been implemented in the correct way ( bad lens design ) .




Maybe blende8 can do some tests on real world examples ? pls

All the best,
Kostas

Last edited by mer; 02-27-2009 at 10:21 AM.
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