懷舊篇之傻瓜照相機介紹

今天接到老朋友的信，互相拜年一番。想想上次聯係的時間是去年春節還是前年春節都不記得了，時間過的真實太快。歎息之餘心裏也有安慰，朋友永遠都不會陌生，無論何時何地。正所謂但願人長久，千裏共嬋娟。

回頭在計算機中找到當年彼此的通信，曾經因為朋友簡單的打聽，就竭力賣弄當時對照相機的了解。現在在翻開來看，竟然不算太膚淺。放在這裏，也算個紀念。畢竟是十幾年前的話題了，可能對有些人來說，連懷舊的感覺也不能體會了。

下麵是其中的三封信，其中第三封還比較可讀，所以把順序倒過來。

給老同學的第二封信: 有關照相機的術語解釋

陸兄:

你好!

來信收到,看信中的內容顯然相機還沒有買,這種速度很成問題,利率下調聽說了吧,下一次經濟騰飛或者叫INFLATION馬上就要來了.趕快花錢吧.信中說讓我科普一下,並不敢當,但見博士的問題實在太薄(對不起),忍不住要賣弄一番.

從信中所提的問題看,仍是情鍾傻瓜相機,真傻瓜也.

照相機的發明起源於人們對針孔成像技術的發現和利用,早在宋代,我國的大聰明人沈括就在其所著的《夢溪筆談》中介紹了這一現象,所以說發明照相機的光榮應屬於中國人,後來我們的祖先忙於打仗搶糧食編故事寫曆史書,反被吃了生牛肉沒喝中國茶葉不消化而坐立不安蠢蠢欲動的西洋人首先將這一技術應用於繪畫,製成了臨模箱,再用瀝青最終是鹵化銀製成了底片,終於按照中國人的想象發明了,其實是仿製了實用的照相機.

可以想象針孔成像中的針孔愈細則成像愈清晰但也愈暗,因為相對於暗箱來說,針孔是成像的通道更是唯一的光源.後來隨著技術的進步,人們又采用了凸透鏡代替不實用的針孔,其最大的優點是可將照射在透鏡表麵上的所有光線,校正"縮小"至近於針孔般的一點,就是說照射在透鏡邊緣的光線與照射在中心的光線通過透鏡後都仿佛來自同一點,從而既保證了成像的亮度又達到了一定的清晰度,但透鏡並不能完全等價於針孔,其成像的清晰度有一定的範圍和限製.從理論上說,透鏡的有效通光孔徑越小,其性能越接近針孔,但此時的成像也就越暗;透鏡的有效通光孔徑越大,其成像越亮,但清晰度的範圍就越窄.這就是現代相機中光圈的作用.光圈的準確定義是焦距與有效通光孔徑的比值,這二者與光強均為平方關係,所以光圈值倒數的平方與膠片所受光照強度成正比,再乘以一常數及曝光時間,即為曝光量,顯然所得曝光量為單位麵積的曝光量,這正好用來比較各種不同尺寸間膠卷的靈敏度.

由於實際使用的透鏡並非如理想透鏡那樣厚度為零,所以在實際使用中就會不可避免地產生各種像差和畸變,所以為提高成像質量特別是鏡頭價格,人們飲鳩止渴地設計了許多種包含多個鏡片的複合鏡頭,在複合鏡頭中,鏡片們亂其八糟地擺放,每兩個相鄰空隙之間的鏡片無論幾個(如超過一個,一定是粘在一起的),都稱為一組,所以鏡頭有9片7組,10片8組等等.鏡頭中鏡片的多少並不能說明成像質量的好壞,如宣傳廣告中出現類似詞句,除眩人耳目外,並無其他含義.

以前所有的透鏡,其表麵必定是某一半徑球麵的一部分(由於研磨所至),所以又稱球麵透鏡.近年來有些聰明人想到采用非球麵透鏡來進一步提高成像質量並獲得了成功,所以采用非球麵鏡片的鏡頭很出了一些風頭,這與其說是因為其成像素質高,倒不如說是因為玻璃鏡片的加工研磨費用昂貴所至.時至今日,多數相機配備了自動聚焦功能,用可憐的電池去推動沉重的玻璃鏡片顯然已不合時宜,且高分子材料日新月異,成像質量也是馬馬虎虎,所以很多鏡片均是用塑料通過模具澆鑄流水線生產而成,其質量也因其所用材料及加工設備的不同而相去甚遠.此時的非球麵鏡片的加工費用已與普通鏡片相差無幾.製造商們所吹噓的輕便相機鏡頭中的非球麵鏡片,其製造成本固然平平,而其對成像質量的貢獻恐怕也是很有限的.

事實上,塑料鏡片的大量泛濫,也是攝影迅速普及的要求,目前的自動聚焦已然如此的完善且便宜,使得輕便相機無不趨之若鶩,而塑料鏡頭的最大的好處就在於可使小巧的輕便相機配備大範圍的變焦鏡頭並利用有限的電池驅動.目前輕便相機的自動聚焦均是通過發射紅外線,然後檢測反射回來的紅外線的角度相位等等判斷物體的遠近.由於裝置的簡陋,所處理的紅外線實際上是較粗且發散的光柱(這正好適用隨便的傻瓜相機),所以自動聚焦有一粗略的範圍.最唬人的是所謂的智能自動聚焦,臉皮薄的廠商稱為多點自動聚焦(MULTI AUTO FOCUS),即向取景畫麵中的三個區域(即照片中最容易有人的地方)同時發射紅外線並測定距離然後取其中距離最小者為依據驅動鏡頭,缺德的是所有的廠商均不公開其"智能聚焦"的範圍,使得使用輕便相機的聰明用者在拍攝立式照片時心中惴惴不安,即使橫握相機拍攝如門內人物之類的畫麵時也不得要領.與之相比,輕便相機推廣初期所設置的單點自動聚焦功能(SPOT AUTO FOCUS)反倒穩妥得多,這種相機要求在對焦時先將對焦框瞄準希望的物體或人,半按快門鎖定焦點,保持半按快門狀態並重擔新構圖,最後釋放快門.顯然這種方法不易出錯,這可能也許是不少廠商在其重要品牌相機上雖然都采用了多點對焦功能,但同時也設置可隨時轉換的單點聚焦功能的原因.

不論多點或是單點自動聚焦,半按快門時焦點(物距)即被鎖定,等到快門最後釋放時則以鎖定的焦點調整鏡頭,所以需要一定的快門延遲時間,而在測距到全按快門的這段時間內主體的位置發生變化,則倒黴活該.廠商大概覺得這樣太不成話,所以又設計了所謂的連續自動聚焦功能(CONTINUE AUTO FOCUS),在此方式下,半按快門後,相機即以每秒若幹次的速度不停地測量主體距離,同時鏡頭也隨之調節,其最大的好處是快門延遲時間短,適用於高速動體攝影.

現代相機特別是輕便相機的另一個特點是其自動曝光功能,其實是自動測光功能.一般是將取景畫麵分成三五七份,分別測量其亮度,然後根據所謂的專家經驗強加一權重值,最後得出曝光值.這中間有很多諸如模糊邏輯之類的唬頭,但這必然有一個問題,就是假如一個智商平均的傻瓜拍照,顯然沒有問題.如果是一個特別傻的傻瓜或是不太傻的傻瓜的話,結果就很難說了.另外需要揭發的是所謂的自動逆光檢測功能,實際上就是比較畫麵中心與邊緣部分的亮度差,如果中心部分暗於邊緣部分且超過一自作聰明的限定值時,相機即作出主體處於逆光的判斷並自動加以補光,舉例來說,江澤民和李鵬與站在中間的曼德拉用輕便相機合影時,半按快門,內藏閃光燈就會自動充電,並在快門釋放時對主體加以補光.

總而言之,現代相機,包括其他產品在內,其更新換代的過程及方向,集中體現了其設計者對人類平均能力的越來越清醒的認識,或者說是越來越傲慢的偏見.一個有力的佐證就是現代相機中所謂的DX碼自動識別係統.所謂的DX碼,是柯達公司最先炮製的,具體就是暗盒輸片口旁的兩列黑白相間的方塊,白色方塊為裸露的金屬部分,黑色則為塗漆絕緣部分,方塊的不同排列方式分別表示膠卷的感光度及張數等諸如此類的信息,在相機的暗盒倉內與每個方塊對應的位置上都設有一對金屬觸點.通過這種方法自動設定膠卷的主要是感光度等信息.其實當前我等所用均為ASA100膠片,最多少數高級人物偶爾眩耀一下ASA400膠卷,這隻需普及幼兒園教育即可解決或替代這一問題,實在不必如此脫了褲子放屁.況且輕便相機中具備此功能後已不能手動設定,也沒有任何顯示,不單目前國產黑白膠卷都不能使用.假如你領著女朋友出去玩同時又眩耀新買的照相機,偏偏膠卷暗盒上的信息區或被粘汙或被劃傷,則相機必然以錯誤的曝光組合工作,整卷膠卷不是曝光過度就是不足,最不幸的是沾沾自喜的你毫無知覺,對即將產生的嚴重局麵及其衍生出來的更嚴重的後果一無防範.

目前在市場上占據統治地位的高檔輕便相機多具有內置2-3範圍的變焦鏡頭,這不僅帶來了方便更增添了樂趣.變焦範圍的選擇除了有關價格的考慮外,更應從中國的實際出發,選擇有中國特色的照相機.在中國,不像外國那樣,稀稀拉拉的沒幾個人,有人也不往一起湊,中國講求的是團結,要的是凝聚力,所以公園景點人山人海,如想單獨留影一張,非把相機鏡頭杵到被攝者的鼻子上不可.此時方顯短焦距鏡頭之妙用,故此我一口咬定變焦範圍一定要從28毫米開始.蓋鏡頭焦距f,像距v和物距u有如下牽扯:1/f=1/v+1/u,物距太大,所以像距與焦距近似相等,設d為膠片畫麵上對角線長度,則以d的兩個端點及鏡頭的中心點可作一三角形,其高度為v,而其頂角即為成像最大涵蓋角.底邊d長度恒定,則高度v越小,成像角度越大也.

輕便相機的最大目標是追求完全的自動化,恨不能把照相機設計成機器人.遺憾的是這一目標還很遙遠,目前的相機在卷片,對焦和曝光等功能都基本上自動了,最礙眼就數變焦了,設計大師們窮思竭慮,終於有所交待,即所謂的人像功能(PORTRAIT MODE).人像功能的具體實施方法是設定此功能後,相機測定主體距離,根據此距離調節鏡頭焦距,調節的依據是使不同距離的人在底片上的成像大小趨於一致,如證明像,半身像像之類的統一格式,這是一很令人費解的功能,如采用此功能拍滿一卷膠卷的話,出現在底片上的豈不是一排一模一樣的呆瓜?

輕便相機得以迅速普及的重要武器之一即是其內藏的閃光燈,使得房間內及夜間攝影變得輕而易舉,雖然照片糟糕無比.事實上就連高級單反相機的設計者們也發現了這一愚蠢並可供利用的想法,紛紛在許多極具端莊及嚴肅的單反相機內裝上了內置閃光燈以迎合廣大的傻瓜,也不介意相對少數的不太傻的傻瓜望而卻步.不過設計者的本能仍使其在高檔輕便相機中普遍設計了閃光燈取消功能.無論如何,閃光燈已成為輕便相機的招牌之一(目前市場上的輕便相機中唯一不設置閃光燈的是柯尼卡出的高檔機,英文名記不清了大概HEXER類似,中文名叫"巧思"的,萬把塊錢).其功能也令人頭暈眼花,唯一較為實用但又不為人稱道的是閃光燈自動變焦功能(AUTO FLASH ZOOM),在拍攝中閃光燈的照明角度無疑應稍大於鏡頭的涵蓋角,但在高檔輕便相機中由於變焦鏡頭的關係,鏡頭的涵蓋角度有一個非常大的變化範圍,如將閃光照明角度固定在最大值上無疑會造成很大的浪費,故此特將閃光燈燈室的結構設計成可變的,使射出光線的角度可以在某種程度上調節,而這一調節是與鏡頭變焦同步進行的,其優點是既節約了電能又增加了閃光燈的使用範圍.

聰明人都知道黑暗中直射的單燈閃光照明必然會產生呆板單調的影像外加討厭的黑影,對此某些設計者采用了掩耳盜鈴的方法,設計出了所謂的"柔和閃光(SOFT FLASH)"功能,在此功能下工作的相機采用漫射屏或散射屏附加在原來的透射屏上,使光源由原來的閃光管擴大至整個閃光屏,用心雖然良苦,效果卻十分有限.以前攝影書中介紹過的用手帕蒙在閃光燈上以減小反差的方法便是此項設計的指導思想.

由於前些年輕便相機,特別是簡易傻瓜機的迅速普及,作繭自縛的廠商們已開始嚐到市場提前飽和所帶來的苦果,現在隻得拚命地花樣翻新以吸引消費者,甚至不惜以摒棄辛辛苦苦攢起的家底為代價,推出所謂的APS(ADVANCE PHOTOGRAPHY SYSTEM),其實就是帶磁帶的膠卷,來吸引消費者.原來的體係也作垂死掙紮,推出了所謂的PANORAMA攝影方式,即在24X36毫米的底片上拍成13X36毫米的格式以求刺激,其廠商的發言人毫不臉紅地承認,該方式就是要刺激消費者以新的格式拍攝以增加膠卷的銷售.自然,新出的拍馬屁衝印係統兼容了這一格式.

另外再有一事相煩,我因拍幻燈片上癮,特別是翻拍圖片的喜歡.欲買一攝影燈,在大連看有兩種規格單燈頭和雙燈頭的,我覺得價格有些宰人,故請你在逛專業店時看一看北京的價格,如相差不大的話我就買了.牌子是雅剛(ARKON?),名子是鹵素燈或攝影燈,燈頭的形狀有些像首飾櫃台內的照明燈,同時替我看一下放大機,洗片鼓的規格及價格,再就是幻燈片框的價格.希望你早去逛商店,我能早得回音.

別不多寫

祝身體健康!思想活潑!

1996.7.12

老同學之前的回信摘要:

仍想買輕便照相機，希望詳細介紹以下廣告中常見的術語：

光圈與透光量、景深之間的關係，鏡頭的結構，鏡頭焦距與視角的關係，非球麵鏡頭，AUTO FOCUS, CONTINUE AUTO FOCUS, MULTI AUTO FOCUS, SPOT AUTO FOCUS, 智能測光，自動補光，智能自動聚焦，DX碼自動識別，PORTRAIT MODE，AUTO FLASH ZOOM，SOFT FLASH，APS，PANORAMA。

給老同學的第一封信: 照相機的選購

July 9, 1996

Dear Dr.

It is always a great pleasure to share a common topic with a friend. I will be very glad to give you all of my experiences and collections. But first of all, I must inform you that to be an amateur in photography will turn to be very expensive, time-consuming and, in general, fruitless. In fact, this hobby will take a considerable part of your time and salary, in return of which, gives you a lot of proud photos which may seem meaningless to the other persons.

To answer your question about the selection of camera, I suggest you to purchase a camera as good as you can afford now, I mean, with all possible money you can arrange. Remember what your opinion was about 1000 yuan two years ago? and four years ago? and imagine what it will to be after two years. How can you tolerate regretlessly with your Seagull DF-300? A normal camera which is usually designed to last 15 years can not meet the different situations that its owner may suffer during the same time.

For an amateur of photography, the SLR (Single Lens Reflex) camera is an inevitable equipment while the compact camera is in the second range. For you want to practice what you have learned, i.e., to try the combinations of shutter speed and aperture index, the change the depth-of-field, to set the exposure compensation, et al. You buy a camera because you want to TAKE pictures other than to GET pictures, so the more complex the camera is, the more pleasure you will get.

The SLR camera, compared with the compact camera, is more seriously and precisely. When you are plunged in this hobby, you may need to photograph instruments and samples (rocks), or to take picture from screen, magazine and drawing, in which the compact camera can not even to be imagined. The only default of the SLR camera is that sometime it will seem to be a little exaggerating to carry the awful camera and exchange lenses in the daily life, the only exception of which is to be companied by your girl(s).

Your choice of the SLR camera can begin at:

(1) MINOLTA X-700 (~2,500.00)

* Programmed AE (Auto Exposure).

* Manual exposure with lighting meter indicator.

* Programmed flash TTL (Through The Lens) controlled exposure.

* Xsync is 1/60 sec.

* +/- 2 EV exposure compensation.

It is the most classical and common manual focus SLR camera in China, the famous Seagull camera was its unsuccessful replica. It has the most large amount of exchange lenses commercially available than other trademark, for instance, the owner of Canon AE-1P camera will take great effort to find a usable lens (for this reason, I dislike MINOLTA personally).

(2) RICOH XR-8 S/D (~2,000.00)

* Metal body with professional taste.

* Multi exposure.

* Xsync is 1/125 sec.

* Aperture priority AE.

RICOH is the most common trademark because of its price, but the quality and durability of which (both body and lens) can not be trusted. It perhaps a good idea to buy a RICOH body and a SIGMA lens with RICOH mount, so the quality of photo can be guaranteed but the cost is lower. Similarly, there are RICOH SOLAR/D, KR-5III/D, XR-7MII/D selectable, all of which have alike qualities and properties though with many different models.

(3) NIKON FM10 (~4,000.00 with 35-70 zoom lens)

* Metal body with professional taste.

* Manual exposure with lighting metering indicator.

* Xsync is 1/125 sec.

* Multi exposure.

NIKON is the best camera of Japan. NIKON FM10 is a simplification of the famous FM2. It is worth purchasing if the body and lens can be sold separately (the zoom lens involving in set is considered not favourable).

(4) NIKON F801s (~6,500.00)

* Auto focus.

* Programmed AE.

* Xsync is 1/250 sec.

* Multi exposure.

Auto Focus (AF) is the coming thing. It can be predicted that in the near future, most of the major camera manufacturing company will stop producing Manual Focus (MF) lenses, for example, Canon has already. So it will be reasonable to begin with an AF camera.

The major characteristics and specifications of NIKON F801s will be described in a separated paper.

All above is my opinion to choice a SLR camera. If I were you, I will select from NIKON F801s to RICOH XR-8 according to my savings, but a Seagull DF-300 which seems to be cheaper but actually not when considering the cost of the coming repairing, will be certainly out of the question.

For the compact camera, as shown in its popular name, which is designed for housewife or other person similar, can never meet the needs of a man with knowledge and brain. But the compact camera can be a perfect supplementary according to its great convenience, the shooting speed of which is also much superior to the SLR cameras.

The fixed focus compact camera is comprehensible durable and cheaper. But the fixed focus, generally 28 or 32 mm (this is the most important focal length for living photographing), will be very difficulty go give a clear portrait without distortion. So, mainly for the same reason, zoom compact camera in which the focus covers as long as 76 mm or more has been developed and produced.

Several years ago, the zoom ranges of the compact cameras in the market are all begin at 38 mm and end at 76 to 135 mm respectively, it is because of the difficulties from designing and especially producing. As mentioned above, in living photographing, a shorter focal length as 28 mm is necessary to cover a large area or more persons at close distant, for instance, at a crowed park. So many of the famous camera companies have advanced their new kinds of compact cameras recently, like Canon PRIME SUPER 28V, PENTAX ESPIO 928, MINOLTA RIVA ZM 28W et al., in which a shorter focal length of 28 mm are involved.

For some odd reasons, I do not like the SLR cameras with built-in flash, since I believe that direct flash can only produce dull pictures. In the compact camera, however, all of which are equipped with flash, then I despise the kind in which have the jump-out flash (unfortunately, your pre-camera happened to be of this kind, I am sorry), for I believe the jumping (or its cause of flash will certainly consume some energy of battery, and what is more, the jumping will possibly do harm to the camera. In some kinds of compact cameras, the flash zooms synchronously with the lens, so the camera with a jump-out flash must involving a complex and then something dangerous construction.

So much is my opinion to compact camera, the most important of which is the zoom range must cover a 28 mm focal length. So the choice is greatly simplified, for only few cameras can meet this claim, they are Canon PRIME SUPER 28V, PENTAX 280P, PENTAX ESPIO 928, PENTAX ESPIO 628, PENTAX ESPIO W, NIKON TW ZM85, Olympus AZ 220 SZ, RICOH RZ105 ZOOM, MINOLTA RIVA ZM28W et al. I have bought a PENTAX ESPIO 928 two years ago and was satisfied by its performance.

With this letter, I have enclosed a comparison table of some compact cameras and two articles about compact camera written in the last winter, which had been submitted and not published nor even accepted. So you may be the only serious reader of mine. Some contents of the articles may be a little outmoded and need to be replaced, for example, the Canon S 28V should be involved in the articles.

The definition your demanded are list after the articles.

I have never been discussing such and interesting topic with a friend like you, so I would greatly appreciate your continuation.

Your sincerely