[vision01]

有個fd叫我買Pentax *istDS, 唔知大家點睇呢?

[@PICO@]

D70 或 300D ，若等得，等到 5 月PMA 後再買

[wklouis]

PentaxSLR/DSLR都較少人用, 想借配件/鏡頭都難D.
N記和C記好多人玩開, 唔係咁多錢買鏡頭都好易問人借到不同鏡頭來玩.
而且有問題都會多D人可以俾到意見你. 價錢又唔係差咁遠.

[vision01]

睇spec, pentax真係好似幾輕下, 幾吸引,
但的確少配件, 同埋少人玩.

[Elliott]

如果要輕便 *ist DS 同 E-300 都係非常好既選擇而且價錢又平...
唯一係 少d accessories 揀囉... 不過如果你可以睇o岩左 accessories (如 鏡､燈 等...) 先揀機 我諗會好d

[CYY]

我都打算轉玩DSLR，正考慮買E300，因為之前用開5060，有閃燈、電池和搖控可以共用。

以七千多元KIT套裝的價錢，E300確真很抵玩！唯一問題是鏡頭問題，E300只能用4/3系統的鏡頭，用不到一般副廠鏡，而現時4/3鏡只有九支，而且價錢不平！

昨天在O記陳列室個SALE說明年初有支40-150(等於80-300)會推出，價錢太約是二千多元！那麼，支KIT鏡有28-90，而用多二千多元買多支80-300的話，平平地都可以兩鏡走天涯！

[honyeong]

CYY 兄，我是新手，但我看到你諗?用40-150鏡變成80-300?用我有一d可能不正確的?想提提你。
40-150鏡用在E300會變成80-300的成像好似是指當把主體zoom到150mm時，成像會被裁剪成好像zoom到300mm的等同大小，但其實主體仍然只係被zoom至150mm（我指由遠處zoom埋來的意思--我新仔唔多識點講才?，希望你明白我想講乜），而主體根本上並沒有被zoom至300mm。
我講呢d?因我怕你像我早前的想法。如果E300可把40-150mm 鏡變成80-300mm 鏡用，咁豈不是我可以把更遠的?zoom埋?囉？ 其實咁諗係唔?。

[zeusho]

To honyeong朋友：

相信錯的是你。Olympus 4/3系統是 2x factor，鏡頭焦距雖然是14mm，但實際焦距效果是14 x 2 = 28mm…其他的DSLR都有其的系數，有些是1.5x，有一些是1.6x。

[zeusho]

To honyeong朋友：

http://www.dpreview.com/learn/?/Glossary/Optical/Focal_Length_Multiplier_01.htm

Focal Length Multiplier

Many digital SLRs have sensors smaller than the sensitive area of 35mm film. Typically the sensor diagonal is 1.5 times smaller than the diagonal of 35mm film.

As a consequence, a sensor smaller than a 35mm film frame captures only the middle portion of the information projected by the lens into the 35mm film frame area, resulting in a "cropped field of view". A 35mm film camera would require a lens with a longer focal length to achieve the same field of view. Hence the term Focal Length Multiplier (FLM). The FLM is equal to the diagonal of 35mm film (43.3mm) divided by the diagonal of the sensor. Let's now discuss two cases.

Practically speaking this means that a 19mm lens fitted onto a digital SLR with FLM of 1.5X will generate the field of view of a 28mm lens fitted on a 35mm film camera. This disadvantage on the wide angle end becomes a benefit on the tele end. For instance, a 200mm lens on a digital SLR with FLM of 1.5X will have the field of view of a 300mm lens on a 35mm film camera which would be heavier and more expensive. Also because the 35mm equivalent field of views are achieved with shorter focal lengths, the depth of field is larger (2).

"Digital" SLR Lenses
Most digital SLRs are able to use conventional 35mm lenses. However, such lenses are designed to create an image circle that covers a 35mm film frame and are therefore larger and heavier than necessary for sensors which are smaller than a 35mm film frame. "Digital" lenses (e.g. Canon Short Back Focus Lenses, Nikon DX Lenses, Olympus 4/3" System) are lighter because their image circles only cover the sensor area.

[CYY]

贊同！

同樣，為何DC可以那麼容易做到432mm？是因為DC的CCD體積比菲林細得多，做成極大的焦距系數，就我所了解，P記Z20CCD只有1/2.5吋，其原來焦距只有72mm，x6倍後就等於432mm！

[lewismwong]

其實honyeong兄講的才對！

[Lucifer]

唉~~~ 唔識英文就唔好 quote DC Preview 了

以其中一句為例

"For instance, a 200mm lens on a digital SLR with FLM of 1.5X will have
the field of view of a 300mm lens on a 35mm film camera"

200mm鏡頭用落 crop factor 1.5x 的 DSLR, 有如 35mm底片機的 300mm視角.

是視角, 或可以說是焦距轉換了, 光學上那仍然是一支 200mm 鏡頭, 何來 "實際焦距" 改變了!? 改變的只是被拍攝物跟相片的比例增大了, 令你錯覺誤以為 "zoom 遠了"

[CYY]

lewismwong兄：

可否解釋一下呢？

[honyeong]

zeusho 兄，多謝指教。
根你所講，咁係唔係話 … 舉例主體在500 meter 外，用枝40-150mm 鏡向E300到，zoom到盡（我指光學方面）得到的成像等如80-300mm 用向(33mm)菲林機到？
我似為你所講的2x、1.5x、1.6x factor 是指「焦距增長」，如果係咁就好似我的憂累都有一定理由。
其實我所指的zoom 是指純光學變焦方面，而不計digital變焦。
請不要見怪我呢個新仔d愚見。

[lewismwong]

To : Lucifer
雖然你語氣重了些，但抖正很多人對crop factor的錯誤想法，對用dslr的人很重要。
Thanks.