This page will chronicle various accessory finders for 35mm, medium-format, and digital cameras.  I will add more throughout September 2009.

Cosina plastic viewfinders (15mm, 21mm, 24mm, 28mm, 35mm).  These pop up under a number of names: Cosina, Voigtlander, Ricoh (GV-1), Epson (RD-1 finders), possibly also Konica.  They all feature a plastic unibody (body and foot) and coated optics.  Some focal lengths have framelines, others do not.  These were a good value for the money at $99, but for what some of these command, you might look elsewhere.

- Clarity: excellent

- Distortion: visible, more so at the wider focal lengths

- Eye relief: adequate for eyeglasses but within bounds

- Frameline accuracy: conservative

- Parallax correction: in finders with framelines, shown by a dotted line (also serves as a field corrector).

- Materials: plastic, multicoated glass

- Size/weight: very small, very light

Epson RD-1 finders.  See Cosina plastic finders above. These are very specific to the fields of view created by putting typical 35mm focal lengths in front of a DX sensor.

Kodak Retina 50/90mm Sport Finder.  A bit smaller than the Leica equivalent (ROSOL), the Kodak finder is a nicely made flip-up frame finder that covers 50mm and 90mm focal lengths.  The one thing that is not very convenient about this finder is that to see  the 50mm frame, you need to flip the 90mm mask and 90mm eyepiece restrictor out of the way.  But for what it sells for, it's a solid piece of work.

- Clarity: excellent

- Distortion: none

- Eye relief: poor

- Frameline accuracy: conservative

- Parallax correction: yes, via moving the rear eyepiece

- Materials: chrome-plated brass, spring steel

- Size/weight: very light.  Folds flat onto camera.

Konica M-Hexanon Dual 21-35mm finder.  This resembles the Cosina plastic finders (see above), but it's larger and a bit less distorted.  Has 21mm and 35mm frames, parallax corrected.

Mamiya Super 23 Wideangle Finder (65mm).   One thing that cannot be ignored is that there is a direct relationship between the size of an accessory viewfinder and how low its distortion is.  The Mamiya has this covered; it is a very big finder with very low distortion.  As an added bonus, it also has a cold shoe on its top.  This finder is relatively easy to disassemble to insert a Wratten 90 viewing filter.

- Clarity: excellent

- Distortion: very low

- Eye relief: good

- Frameline accuracy: conservative (6x9 with 6x7 markers)

- Parallax correction: yes, via moving the rear eyepiece

- Materials: glass optics painted die-cast body, chrome-plated brass shoe and foot; aluminum distance scale, plastic eyepiece frame, plastic retainer for optics.

- Size/weight: big but not particularly heavy.

Ricoh GV-1.  See Cosina plastic finders above.  The GV-1 differs primarily in that it shows dual 21mm/28mm frame equivalents and is offset to accommodate the popup flash on the GR Digital series.

Tewe 35-180mm Zoom Finder.  This finder, copied both by Nikon and Canon for their rangefinder cameras, uses a combination of changed magnification and apparent frame size to cover the range from 35mm to over 180mm.  There is a parallax corrector on the mounting shoe.  Like all parallax correctors, you will forget to use it.

- Clarity: suprisingly good given the all-around nature of the finder

- Distortion: minimal

- Eye relief: passable

- Frameline accuracy: conservative

- Parallax correction: yes, but not field correction.

- Materials: uncoated glass optics, metal barrel, metal focal length ring, metal frame mask, metal eyepiece.

- Size/weight: reasonable but not lightweight.  Suitable for a compact camera, barely.

Voigtlander Kontur.  This is Voigtlander before the bodysnatcher Cosina got to it.  This is an ingenious (and very small) finder that is available in 2x3 and 6x6 formats (always normal lenses).  It uses a high-powered positive lens to focus your nondominant eye on a brightline mask.  Keep both eyes open, and you can see the frames projected onto your subject.

- Clarity: as good as your eyes

- Distortion: slight distortion in the framelines, none of the subject

- Eye relief: very good

- Frameline accuracy: very conservative

- Parallax correction: yes, but not field correction.

- Materials: acetate mask, plastic body, glass lens, metal shoe

- Size/weight: neglible on both counts

Voigtlander Turnit (Original 35/100mm).  The same person at Voigtlander who figured out that you could use an optical illustion to project framelines into a user's stereo vision also realized that the magnification of a 35mm finder is roughly the reciprocal of a 100mm finder.  The result is the Turnit, which can be rotated 180 degrees to be either a passable 35mm finder or a decent 100mm finder.

- Clarity: very good at 100mm, ok at 35mm.

- Distortion: slight distortion at both settings.

- Eye relief: very good; like the Kontur, it is spectacle friendly (and, inexplicably, the 35mm frame is much clearer when you set your eye back slightly).

- Frameline accuracy: conservative

- Parallax correction: yes, but not field correction.  Rear eyepiece/lock moves up and down.

- Materials: uncoated glass optics, bakelite body, metal shoe and eyepiece/locking mechanism.

- Size/weight: much bigger than it looks in pictures.  This is not all bad; the size of the finder makes the clarity that much better.

- Use for: your Micro 4/3 camera for which you use a 17mm Olympus lens and a 50mm Leica lens.