120 vs 220

Total newbie to medium format, with a newly-acquired used Mamiya m645 (J?).

Apparently it has cassettes or cartridge that allow it to take "120" or "220" format.
But ... How are they different?
Are not the images the same dimensions?
(6mm x 4.5mm?)
Is it just a matter of how long the roll of film is,
and therefore (a) how many pictures can be taken on a roll,
and (b) how big the cassette is?

MangroveRoot asked:

Apparently it has cassettes or cartridge that allow it to take "120" or
"220" format.
But ... How are they different?
Are not the images the same dimensions?
(6mm x 4.5mm?)

Yes.

Is it just a matter of how long the roll of film is,

Yes.

and therefore (a) how many pictures can be taken on a roll,

Indeed.

and (b) how big the cassette is?

Aren't they (the inserts) the same size?

Are not the images the same dimensions?
(6mm x 4.5mm?)

The units for 6 x 4.5 are cm, not mm , but we knew what you probably meant.

On 2007-06-18, Q.G. de Bakker wrote:
MangroveRoot asked:

Apparently it has cassettes or cartridge that allow it to take "120" or
"220" format.
But ... How are they different?
Are not the images the same dimensions?
(6mm x 4.5mm?)

Yes.

Is it just a matter of how long the roll of film is,

Yes.

And that 120 has a paper back while 220 only has short protective paper strips
at both ends.

and therefore (a) how many pictures can be taken on a roll,

Indeed.

and (b) how big the cassette is?

Aren't they (the inserts) the same size?

The lack of paper enables the rolls to have the same sizes, with ~double the
length of film

HTH

Thierry

The 645 J uses an "insert" to hold the feed roll and take-up
spool. The units include the film pressure plate and frame
counter gear. 120 film has a continuous paper backing taped
only at the leading end; 220 film has a paper leader and a
paper trailer both taped to the film, since the 120 film is
effectively twice as thick (paper + film) it requires a
different pressure plate spacing to stay flat, since the 220
film is "thinner" twice as many frames are wound on the
roll. The inserts fit in fixed back Mamiya's like the "J"
and also in the interchangeable film magazines for newer models.

Inserts come with spiffy plastic boxes so that you can
pre-load and swap inserts for quick shooting.

Since I process my own film and shoot only black and white I
haven't much use for 220 inserts (I hate those extra long
rolls of film both to load and then to handg up to dry) but
they are very convenient when shooting (color) weddings or
aerials.
darkroommike

MangroveRoot wrote:
Total newbie to medium format, with a newly-acquired used Mamiya m645 (J?).

Apparently it has cassettes or cartridge that allow it to take "120" or
"220" format.
But ... How are they different?
Are not the images the same dimensions?
(6mm x 4.5mm?)
Is it just a matter of how long the roll of film is,
and therefore (a) how many pictures can be taken on a roll,
and (b) how big the cassette is?