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A鏡三劍客 [複製連結]

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發表於 2007-2-9 06:16:08 |顯示全部樓層 | 字體大小
A鏡三劍客

我認為,A100/F2.8 Macro是個偷跑出來體會生活的公主,另二位,是默默跟著這位頑皮公主的護衛高手。

這三位皆有FREE(Fixed Rear Element Extension)加持,使得不論在無限遠或最近對焦時,皆能有效控制像場曲率(field curvature)與減少球面像差(spherical aberration)。同時也有效地縮小了體積及重量。

與A100/F2.8 Macro相伴,是一種觀照世間的特殊方式,她總是能看到常人所不覺。

A*85/F1.4有著鑑人明目,就算再怎麼昏暗不明,他也可以讓目標絲毫畢現。

A*135/F1.8如沙場老將,千百人中總是可以開出一條生路,不為外境所拖累。

有幸能與這三位相處,實是福氣。

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有個小問題請教,A*135/F1.8用在K100D上時,光圈可以調到F1.7,很神奇的現象;有人有A*135可以試試,是否為特例個案嗎?

Sr. la disai

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發表於 2007-2-9 08:45:18 |顯示全部樓層 | 字體大小
這三隻真是Pentax光學的高峰啊!
只可惜玻璃太重沒有AF化,
這三隻加起來有超過NT$120,000的身價,
擁有一隻就很值得驕傲了,
一起擁有三隻真是令人稱羨~
(攻擊)(攻擊)(攻擊)

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發表於 2007-2-9 10:42:29 |顯示全部樓層 | 字體大小
關於光圈變1.7的問題,我雖然不知道為甚麼...但是,我手上有一隻sigma 24mm f1.8的鏡頭接在ist *DS上也是到1.7喔~~~~~供參考!!
pentax & canon

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發表於 2007-2-9 11:04:41 |顯示全部樓層 | 字體大小
那是因為相機不認識這顆鏡頭,
所以F1.7是用2的(3/4)次方算出來的,
如果是43le因為相機認得,他就會出現F1.9。

新竹大魔頭

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發表於 2007-2-9 11:20:04 |顯示全部樓層 | 字體大小
Post by benjaminlai;252985
那是因為相機不認識這顆鏡頭,
所以F1.7是用2的(3/4)次方算出來的,
如果是43le因為相機認得,他就會出現F1.9。

喔~又多學到了一些囉!
<img src="static/image/smiley/comcom/3.gif" class="vm">

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發表於 2007-2-9 11:48:05 |顯示全部樓層 | 字體大小
43LE發行時間是1997年
在這之前的早期機身上
像MZ-10也只會顯示2.0

比實際光圈小的就有差了
如果是手動模式就沒關係
但MZ-10用A自動模式時
最大只能開到2.0
心比天高~命比紙薄~ 說的就是我這種人

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發表於 2007-2-10 01:36:18 |顯示全部樓層 | 字體大小
感謝大家的解答!我拿到MZ-6上試了一下,也是如此。

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發表於 2007-2-10 01:45:13 |顯示全部樓層 | 字體大小
感謝大家的解答!我拿到MZ-6上試了一下,也是如此。

光之魔導士

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發表於 2007-2-10 02:43:56 |顯示全部樓層 | 字體大小
I second only the notion for the 100 Macro. In fact if one study the late 90's / current Macro lens and their optical layout, one can easily see that almost all of them had some form of fixed rear group which is being used for flat field correction. This is not at all a new design trick. it had been in use by optical Mfr since the days of Brass Barrel lens ( that is its more than 100 years ).

Pentax own way of that is to use this optical design on FAST long focal for close up correction. Which is why this is tauted in the 135 & 85 A* as well as the 77 Limited. Its use on long focal Macro lens for 35mm film is almost  universal. Even way back with the original Vivitar Series 1 90/2.8 Macro had that !!

To be honest, as a long focal / Short Tele, the A 100/2.8 Macro is very good, but as a Macro lens, the A 100/2.8 is pretty downright disappointing as it shown a great deal of optical fault at the much needed close up to Macro range that is prevelent at all aperture. Somehow the 100/4.0 Macro while not quite as acute and not quite as contrasy. Do resolve almsot the same but less those optical fault ( and for a much cheaper cost at 1 stop slower ) !!
[URL=\"http://m42.povlab.org/site_patchwork.php\"]M42 Project[/URL]

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發表於 2007-2-10 04:15:16 |顯示全部樓層 | 字體大小
Post by FTL;253391
I second only the notion for the 100 Macro. In fact if one study the late 90's / current Macro lens and their optical layout, one can easily see that almost all of them had some form of fixed rear group which is being used for flat field correction. This is not at all a new design trick. it had been in use by optical Mfr since the days of Brass Barrel lens ( that is its more than 100 years ).

Pentax own way of that is to use this optical design on FAST long focal for close up correction. Which is why this is tauted in the 135 & 85 A* as well as the 77 Limited. Its use on long focal Macro lens for 35mm film is almost universal. Even way back with the original Vivitar Series 1 90/2.8 Macro had that !!

To be honest, as a long focal / Short Tele, the A 100/2.8 Macro is very good, but as a Macro lens, the A 100/2.8 is pretty downright disappointing as it shown a great deal of optical fault at the much needed close up to Macro range that is prevelent at all aperture. Somehow the 100/4.0 Macro while not quite as acute and not quite as contrasy. Do resolve almsot the same but less those optical fault ( and for a much cheaper cost at 1 stop slower ) !!
__________________
M42 Project

You are right, FTL. Pentax has officially listed that FREE is used in prime lenses, and Pentax have even used fix rear group in zoom lenses. But in my understand, those are most in so called high-end lenses (in the technical datasheet I can get, Pentax primes, where are only FA77/A*85/A*135/A,F,FA,DFA100Macro2.8/A*200Macro that have FREE design).
And for FREE design, beside positive side, there is negetive effect, too. Lenses featured in FREE are not truely "Fixed focal lenses". The focal length will decrease when focusing to shorter distance. So we can only say they are "Vario focal lenses".

(Data of FREE are from http://www.bdimitrov.de/kmp/)

I personally have a guess, if the field curvature and spherical aberrations is negligible enough for lenses with focal length longer than 200mm, so only lenses in short-telephoto range widely use such technic as FREE??

In my previous experience of 100mm Macro lenses, Nikon 105/2.8, Canon 100/2.8, Pentax FA+DFA100/2.8, Vivitar 105/2.5, Sigma 105/2.8, I can't remember if all the model names in my mind are right, are all good performers. Working with them is happy. And I am now starting to have fun with my A100/2.8Macro.

You have mentioned that there are Optical faults in A100/2.8 Macro. I myself is only a Biologist, not an Optic-Physicist, and I am very interested in this information. Could you talk more on this point/aspect?? I will very thankful for your information.
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