看来这个不许压人的4X5modelD 还行。

From: Tim Takahashi (tim@isaac.me.rochester.edu)
Subject: REVIEW OF PRESS CAMERAS (from 1949)
Newsgroups: rec.photo.equipment.large-format
View this article only
Date: 1996/02/18


In light of additional questions about inexpensive 4x5"
camera's I am posting a slightly edited copy of the
1949 Consumers Reports article titled :

              "PRESS CAMERAS"

(N.B. Bob S. should note that the Linhof is
  referred to in this review as a "press camera." )

  The popularity of the "press" camera among amateur
photographers seems to be based partly on the aura of
expertism such a camera lends to its possessor, partly
on the beliefthat this is the equipment needed to get
a fine, and perhaps saleable picture.

The price is high; no press camera equipped with the
bare necessities for use is inexpensive. The training
needed before the amateur learns the proper use of his
equipment is considerable.

Press cameras are definitely NOT reccomended for the
casual snap-shooter, or beach photographer, or
even for the beginning amateur who may be infused with
enthusiasm but has not yet decided to devote his heart,
soul, and most of his spare cash to producing a salon
print of a "scooping" Weejee.

Functional, any camera which can take news pictures
is a press camera. However, the term is restricted to
the special type of camera most used by news photographers
because it is adaptable to the wide variety of condition
under which they may operate. It should be noted
that IT IS NOT THE BEST CAMERA FOR ANY SINGLE USE
but an ingenious compromise that functions for a wide
range of uses.

These characteristics define a press camera :

- It folds into a strong, compact box
- Lenses can be easily and rapidly exchanged
- It has a light-tight flexible bellows
- Sheet film is used
- It has a ground glass focusing screen
- It can be hand held for picture taking
- It can be brought into action quickly
- It is equipped with a supplementary (non ground glass)
    viewfinder
- Provision is made for using a supplementary
    rangefinder and flash gun.

Most have rising and tilting fronts, two have adjustable
backs. For almost all special applications, the ground glass
focusing screen must be used.

EVALUATION

The same rangefinder, lens, etc. can be attached to
different cameras: to the extent that these control the
quality of the picture no one one press camera is
"better" than anothy. The main questions with respect
to the various features are these : do they extend the
usefulness of the camera? do they improve its durability?
to they make it easier to use? do they permit it being
placed into action quickly?

Some cameras sold as press cameras do not have all the
basic features characteristic of the better designs.
The most popular film size among American photographers
is 4x5".

THE CASE : protects the mechanism and lens. Most are
metal; covered with leather.

THE BELLOWS : should be light tight, flexible, and compress
far enough to permit the use of wide-angle lenses.

THE LENS STANDARD : the lens is mounted on the lens board,
which should be easily removable. In most cameras, the
front standard is subject to several different motions :
it rises, shifts laterally and tilts about a horizontal axis.
In some, the standard can rotate about a vertical axis.

"Triple extension" may or may not provide great bellows
extension. Both LINHOF and KALART had triple extension tracks,
but the Kalart lacked rigidity and had less than 12 inches of
maximum extension. The MERIDIAN had double extension tracks,
but had ususually long bellows draw (15").

THE BACK : The camera back is precision made to hold the ground
glass in place. Most cameras are equipped with revolving backs;
those with fixed backs must be turned on their sides to take
"vertical" pictures.

Two cameras, the LINHOF and MERIDIAN have their backs mounted
on four individual posts, permitting considerable motion. This
allows for a wider range of perspective corrections. It adds
over an inch to the total bellows draw of the MERIDIAN.

RANGEFINDERS : Most cameras make provision for using one of two
standard rangefinders (HUGO MEYER or KALART) coupled to the
primary lens. The best couplings are those in the GRAPHIC,
KALART, BUSCH and LINHOF cameras.

Changing the rangefinder to match another lens placed in the
camera in the field is a feasible operation as yet only on the
LINHOF, and that only to a limited extent. The LINHOF comes
equipped with a special rangefinder and two matched lenses.
The rangefinder is coupled to the focusing track through a
special cam which must be changed to couple the rangefinder
to the new lens.

The BUSCH may be equipped with VUE-FOCUS, a single eyepiece
combined rangefinder/viewfinder. It performs and functions well.

For some photographers, the focusing scale is as important as
the rangfinder. In the MERIDIAN and GRAPHIC cameras, it is
possible to have several different focusing scales on the
camera at one time.

SPECIAL NOTES : (The difference between the Crown Graphic
and Speed Graphic is that the latter has a focal plane as
well as a between-the-lens shutter)

(The Vue-Focus of the BUSCH Pressman combines viewfinder
and rangefinder - the viewfinder has automatic parallax
correction)

(The LINHOF is the only press camera on which the
rangefinder is easily adapted for use with two lenses)

(The MERIDIAN is the most flexible press camera tested.
Some of its motions are illustrated in the multiple
exposure picture at right)

RATINGS FOLLOW -  4x5" PRESS CAMERAS

Top Rated :   BUSCH PRESSMAN MODEL-D
      MERIDIAN 45B

Acceptible :  LINHOF TECHNIKA-III
              GRAFLEX PACEMAKER SPEED-GRAPHIC 45
              GRAFLEX PACEMAKER CROWN-GRAPHIC 45

Downrated :   BURKE AND JAMES "WATSON" PRESS CAMERA
      BACO "PRESS-VIEW"
              "PRESS-KING"

2x3" MINIATURE PRESS CAMERAS

Acceptible :  GRAFLEX PACEMAKER SPEED-GRAPHIC 23              
      GRAFLEX PACEMAKER CROWN-GRAPHIC 23
              BUSCH PRESSMAN MODEL C
Not Accept. : BURKE AND JAMES "WATSON" MINIATURE PRESS
               (rangefinder coupling easy to damage)
              PRINTEX (overly short bellows draw)

有2个家伙在制造虚假繁荣。早离题得一塌糊涂了，还...
打倒2个欺骗了大家感情的弄虚作假者！！！

看了半天也没有找到这个1度点测表在哪里。谁总结一下，到底该买个什么样的点测表啊？

那个后背的改动应该不是那么复杂，上下各弄个下面图中的
塑料片试试，better yet，直接弄俩装镜头板那样的滑片？
实在不行就只好加块木板了，对你来说也不过是a piece of
cake.

seems a bad purchase...

again see see ...

http://cgi_ebay_com/aw-cgi/ebayISAPI.dll?ViewItemRedirect&item=1297635550

那个review好象证明了这个2450没有set focus position功能-在玻璃上的就sharp,
放在holder里的就差些。

另外黑白片用true color扫描是因为：如果选“black and white"那三个CCD中只用
绿色(还是蓝色？)的频道来扫，而绿色频道的噪音最大(红色最小？)所以扫描的质量不
行。如果用true color来扫，即使绿色频道出很多噪音，但这些噪音被其它两个频道
的噪音cancel掉的机会会很大？

http://www_virtualtraveller_org/epson2450.htm

没事撑的,碎步溜去注册成了一个Epson Developer,所以可以DL一些programming guides.
去DL了2450的programming guide,里面25页有如下文字:
This product does not support the focus position setting function. The other of default value is not set. Always 40h.

40h是: The platen glass surface.

所以cmnopx前阵子顶住了还真对?

[碎步溜 编辑于 2001-11-15 03:48 ]

看来firmware/software是有这功能的，但很多model都没有
hardware implementation。也就一个微动开关/微型马达和
相应的装配的cost，但给了厂家给少数model收高价的理由。

碎步溜是不是考虑自己写个driver来充份发挥扫描仪的能力？

只有1600Expression, 1640XLExpression,和1680Expression是支持这个
set_focus_position功能的。
下面是epson.c中的一段code:
if ( strcmp ( "ES-6000", dev->sane.model ) == 0 ||
     strcmp ( "GT-10000", dev->sane.model ) == 0 )
  {
    s->hw->scan_hard = & epson_scan_hard [ 1 ];
    s->hw->cmd->set_focus_position = 0;
  }
else if ( strcmp ( "GT-6600", dev->sane.model ) == 0 ||
  strcmp ( "Perfection610", dev->sane.model ) == 0 )
  {
    s->hw->scan_hard = & epson_scan_hard [ 2 ];
    s->hw->cmd->set_focus_position = 0;
  }
else if ( strcmp ( "GT-7600", dev->sane.model ) == 0 ||
  strcmp ( "Perfection1600", dev->sane.model ) == 0 )
  {
    s->hw->scan_hard = & epson_scan_hard [ 3 ];
    s->hw->cmd->set_focus_position = 0;
  }
else if ( strcmp ( "ES-2000", dev->sane.model ) == 0 ||
  strcmp ( "Expression1600", dev->sane.model ) == 0 )
  {
    s->hw->scan_hard = & epson_scan_hard [ 4 ];
    //s->hw->cmd->set_focus_position = 0;
  }
else if ( strcmp ( "ES-8500", dev->sane.model ) == 0 ||
  strcmp ( "Expression1640XL", dev->sane.model ) == 0 )
  {
    s->hw->scan_hard = & epson_scan_hard [ 5 ];
    //s->hw->cmd->set_focus_position =0;
  }
else if ( strcmp ( "GT-6700", dev->sane.model ) == 0 ||
  strcmp ( "Perfection640", dev->sane.model ) == 0 )
  {
    s->hw->scan_hard = & epson_scan_hard [ 6 ];
    s->hw->cmd->set_focus_position = 0;
  }
else if ( strcmp ( "GT-8700", dev->sane.model ) == 0 ||
  strcmp ( "Perfection1640", dev->sane.model ) == 0 )
  {
    s->hw->scan_hard = & epson_scan_hard [ 7 ];
    s->hw->cmd->set_focus_position = 0;
  }
else if ( strcmp ( "GT-7700", dev->sane.model ) == 0 ||
  strcmp ( "Perfection1240", dev->sane.model ) == 0 )
  {
    s->hw->scan_hard = & epson_scan_hard [ 8 ];
    s->hw->cmd->set_focus_position = 0;
  }
else if ( strcmp ( "ES-9000", dev->sane.model ) == 0 ||
  strcmp ( "GT-30000", dev->sane.model ) == 0 )
  {
    s->hw->scan_hard = & epson_scan_hard [ 9 ];
    s->hw->cmd->set_focus_position = 0;
  }
else if ( strcmp ( "ES-2200", dev->sane.model ) == 0 ||
  strcmp ( "Expression1680", dev->sane.model ) == 0 )
  {
    s->hw->scan_hard = & epson_scan_hard [ 10 ];
    //s->hw->cmd->set_focus_position = 0;
  }    
else if ( strcmp ( "GT-8200", dev->sane.model ) == 0 ||
  strcmp ( "Perfection1650", dev->sane.model ) == 0 )
  {
    s->hw->scan_hard = & epson_scan_hard [ 11 ];
    s->hw->cmd->set_focus_position = 0;
  }
else if ( strcmp ( "GT-9700", dev->sane.model ) == 0 ||
  strcmp ( "Perfection2450", dev->sane.model ) == 0 )
  {
    s->hw->scan_hard = & epson_scan_hard [ 12 ];
s->hw->cmd->set_focus_position = 0;
  }
else
  {
    s->hw->scan_hard = & epson_scan_hard [ 0 ];
    s->hw->cmd->set_focus_position = 0;
  }
其中GT-9700是2450硬件的model号，它的set_focus_position为0，这段下面还有:

if ( s->hw->cmd->set_focus_position )
  {
    if ( s->hw->TPU && s->hw->use_extension )
      {
s->val [ OPT_FOCUS ].w = 1;
sane_optstate ( SANE_TRUE, s, OPT_FOCUS, & dummy );
      }
    else if ( s->hw->ADF && s->hw->use_extension )
      {
s->val [ OPT_FOCUS ].w = 0;
sane_optstate ( SANE_FALSE, s, OPT_FOCUS, & dummy );
      }
    else
      {
s->val [ OPT_FOCUS ].w = 0;
sane_optstate ( SANE_TRUE, s, OPT_FOCUS, & dummy );
      }
  }
这段只对那三个model管用。其它的model的s->val [ OPT_FOCUS ].w在前面已经设为0，
下面这段：

/*
* set the focus position according to the extension used:
* if the TPU is selected, then focus 2.5mm above the glass,
* otherwise focus on the glass
*/

if ( s->hw->cmd->set_focus_position )
{
if (s->val[ OPT_FOCUS].w == 0)
{
DBG( 1, "Setting focus to glass surface\n");
status = set_focus_position(s, 0x40);
}
else
{
DBG( 1, "Setting focus to 2.5mm above glass\n");
status = set_focus_position(s, 0x59);
}

if ( SANE_STATUS_GOOD != status )
  return status;
}
也只是对那三个model管用。其它的model压根就不做这个操作--暗含的意思是这个
focus position不变--一直按出厂的位置。

-------------------------
当然这个是碎步溜的猜测，而且这个linux的驱动程序epson不正式支持，不是epson
的产品，写的也很sloopy,那三个model都是comment掉s->hw->cmd->set_focus_position =0
也许他忘了comment掉2450的了？

那个mat好象在上盖上，刚好遮住了透射光源，所以做透扫
时得拿掉。俺印象中只有selective系列可通过软件调焦。
不过因为镜头焦距很短，景深比较大，偏一点可能没关系。
但LFD里的讨论对这好象还是很concern的。

既然是epson的mask,应该是考虑了焦点的问题的,epson的说明是:
To use the transparency unit, remove the reflective document
mat. If you're scanning slides or film strips, you will also need
to use one of the film holders.

上盖和机器还有个8-9pin的连线,估计你一把这个mat取走,scanner
就转成另一个模式了,焦点就会自动上调?

估计还是得到商店去试试.

如果不想用那克命油大概就得多实验了。俺当年开始放120底片
时自己做了个玻璃底片夹，牛遁环那个多的，就跟看全息图似
的。后来在玻璃上贴一层黑纸，再慢慢改进操作方法，这牛就
给炖没了。俺估计平扫带的那些masks就干这用的。但把底片
抬高又有失焦问题。看来真没有省油的灯。

那个看牛的玻璃俺没用过。俺做底片夹时想过，但因太贵而没
采用。

[cmnopx 编辑于 2001-11-14 08:59 ]

俺原来烤了20G在这盘里，结果分盘时因为俺要前面的扇子来烤
laptop的partition，这20G的玩意得移到下一盘去，俺看PM干了
20分钟，发现至少要十个小时才能干完，就把这20G给干掉了。
从laptop上烤20G的partition只花了俩钟头。

Epson的平扫有可调焦的，就是那selective系列。有点太贵了。

这克命油俺只听过没用过所以心里没底。再说那个操作
又贴胶布又挤气泡的也够麻烦的。

你底下那个漏光问题，可用黑海绵如硬盘或其他计算机
板的保装盒里的那种。用刀片割下细细的小条塞在后门
槽里即可。

俺楼下说的那盘子被俺用PM7给分了。还把laptop里的
整个partition给拷过去。极慢，比俺想象的慢多了。

俺这一老哥买了Canon新出的FS4000，死活要俺买你说的那个Epson
和他share。俺一直顶着。俺对平板透扫总有那么点不放心。前几天
看了些LFD上扫大底片的帖子，其中说到的牛顿环和对焦等问题使俺
更加犹豫了。你的看法？