CONTAX CLUB Carl Zeiss 討論區

Does anyone know how to calculate the usable aperture of ZM lenes on R3A and ZeissIkon etc?
R3A has 1.0 magnification while ZeissIkon's is 0.75, does this help R3A increase accurancy on focusing?

兩部機都係M-MOUNT , 唔係改MOUNT 機, 故此可用光圈應該相同.



放大率唔同, 最主要係放便人去對焦時好睇啲, 咁就會準啲. 特別係用啲較長焦距嘅鏡時(雖然RF 機比較少TELE-PHOTO鏡).
但另一方面講, 因為放大率高啲, 咁部機都要做係對焦上加強番先至得嘅, 咁......你都可以話高放大率嘅機係對焦上係會準確啲嘅.....

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I LOVE ALFA ROMEO

What I'm saying is something like the relationship between "range finder base" and "circle of confusion".
If you could perceive that the focusing accurancy of range finder cameras is depend heavily on relationship of circle of confusion and range finder base distance, you will understand why ZeissIkon emphasize on the fact that it is the range finder with widest base on the market.
My question is will the R3A's higher magnification makes its accurancy comparable to ZeissIkon?

ZEISS 未出就真係唔啦!
但R3,R2 我自己都有發覺就真係唔係大準啦. 不過我諗都係佢對對焦眼生得太近所至.

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I LOVE ALFA ROMEO

呀, 不過睇嚟就算ZEISS部機未到都估到佢實好過R3機.
你睇吓ZM部機嗰對對焦眼生得幾開, RF機好唔好真係有樣睇.

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I LOVE ALFA ROMEO

R3A have 1.0X magnification when using it's 40/1.4 lens only....

Does anyone really understand what the question about?

Do you mean something like this.

http://www.imx.nl/photosite/leica/technics/rfaccuracy.html

Yes, exactly.

The answer should be Yes if R3A is compared with R2A, but NO while compare with Zeiss Ikon!

The focusing accuracy for the range finder should be determined by the effective base length [EBL], which refers to the magnification of the finder times the base length of the range finder system.

For R3A: EBL = 1.0 X 37mm = 37mm

For Zeiss Ikon: EBL = 0.74 X 75mm = 55.5mm

While we compare with Leica MP / M7......

For 0.58: EBL = 0.58 X 68.5mm = 39.73mm
For 0.72: EBL = 0.72 X 68.5mm = 48.32mm
For 0.85: EBL = 0.85 X 68.5mm = 58.225mm

While for vintage Leica M3.............

EBL = 0.91 X 68.5mm = 62.335mm

so one can assume that the focusing accuracy of the Zeiss Ikon body should lie between Leica MP/M7 0.72 and 0.85. However, the focusing accuracy of a RF should be further affected by the constrast and the brightness of the viewfinder, as well as the resistance to the flare etc. The actual performance for the Zeiss Ikon viewfinder should be determined by the end users when they really come out in the next month, yet its high eye-point design should be one of the great advantage for the majority of the eye-glassed users here in Hong Kong...............

Here is a link from Camera Quest as reference:

http://www.cameraquest.com/leica.htm

The article from Erwin Puts should be valuable for reference on this topic too

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Wah
理事 - Board of Members
www.flickr.com/dicksonlau

Thanks for sharing.