<s>
The	O
T-mount	B-Algorithm
is	O
a	O
standard	O
lens	B-Algorithm
mount	I-Algorithm
for	O
cameras	O
and	O
other	O
optical	O
assemblies	O
.	O
</s>
<s>
The	O
usual	O
T-mount	B-Algorithm
is	O
a	O
screw	O
mount	O
using	O
a	O
male	O
42×	O
0.75	O
(	O
42mm	O
diameter	O
,	O
0.75mm	O
thread	O
pitch	O
)	O
metric	O
thread	O
on	O
the	O
lens	O
with	O
a	O
flange	O
focal	O
distance	O
of	O
55mm	O
and	O
a	O
mating	O
female	O
42mm	O
thread	O
on	O
a	O
camera	O
adapter	O
or	O
other	O
optical	O
component	O
.	O
</s>
<s>
This	O
thread	O
form	O
is	O
referred	O
to	O
as	O
T-thread	B-Algorithm
.	O
</s>
<s>
(	O
This	O
should	O
not	O
be	O
confused	O
with	O
the	O
M42	B-Algorithm
lens	I-Algorithm
mount	I-Algorithm
which	O
is	O
also	O
42mm	O
diameter	O
,	O
but	O
has	O
a	O
1mm	O
thread	O
pitch	O
.	O
</s>
<s>
The	O
T-thread	B-Algorithm
is	O
sometimes	O
described	O
as	O
"	O
M42×	O
0.75	O
,	O
"	O
which	O
is	O
the	O
usual	O
manner	O
in	O
which	O
to	O
describe	O
a	O
metric	O
thread	O
.	O
)	O
</s>
<s>
The	O
"	O
T	O
"	O
is	O
said	O
to	O
stand	O
for	O
Tamron	O
or	O
Taisei	O
,	O
a	O
Japanese	O
manufacturer	O
that	O
released	O
in	O
1957	O
the	O
first	O
of	O
a	O
line	O
of	O
aftermarket	O
camera	O
lenses	O
that	O
fit	O
35mm	O
SLR	O
cameras	O
built	O
by	O
various	O
manufacturers	O
using	O
their	O
universal	O
T-mount	B-Algorithm
.	O
</s>
<s>
On	O
the	O
first	O
model	O
,	O
the	O
mini	O
T-mount	B-Algorithm
used	O
a	O
M37×	O
0.75	O
thread	O
;	O
Tamron	O
's	O
canonical	O
M42×	O
0.75	O
T-thread	B-Algorithm
did	O
n't	O
appear	O
on	O
the	O
market	O
until	O
about	O
1962	O
.	O
</s>
<s>
The	O
company	O
referred	O
to	O
it	O
variously	O
as	O
a	O
T-mount	B-Algorithm
,	O
T-thread	B-Algorithm
,	O
T-adapter	O
,	O
or	O
a	O
T-400	O
,	O
but	O
not	O
as	O
a	O
T-2	O
,	O
which	O
is	O
simply	O
the	O
name	O
that	O
Soligor	O
used	O
for	O
its	O
version	O
of	O
the	O
T-adapter	O
.	O
</s>
<s>
The	O
proprietary	O
lens	B-Algorithm
mount	I-Algorithm
of	O
each	O
camera	O
manufacturer	O
was	O
adapted	O
to	O
the	O
T-mount	B-Algorithm
thread	O
with	O
a	O
simple	O
adapter	O
.	O
</s>
<s>
Some	O
T-mount	B-Algorithm
lenses	O
accept	O
a	O
T-adapter	O
that	O
lacks	O
its	O
threaded	O
inner	O
ring	O
,	O
and	O
simply	O
slides	O
onto	O
the	O
T-mount	B-Algorithm
lens	O
.	O
</s>
<s>
As	O
a	O
common	O
mechanical	O
interface	O
,	O
the	O
T-mount	B-Algorithm
allows	O
components	O
of	O
various	O
manufacturers	O
to	O
be	O
interchanged	O
and	O
assembled	O
.	O
</s>
<s>
The	O
T-mount	B-Algorithm
is	O
a	O
solely	O
mechanical	O
specification	O
.	O
</s>
<s>
Besides	O
cameras	O
,	O
T-mounts	B-Algorithm
are	O
used	O
in	O
optical	O
breadboard	O
prototyping	O
components	O
as	O
well	O
as	O
telescope	O
and	O
microscope	O
attachments	O
.	O
</s>
<s>
The	O
T-mount	B-Algorithm
is	O
also	O
a	O
standard	O
way	O
to	O
mount	O
a	O
camera	O
to	O
a	O
microscope	O
to	O
photograph	O
pathological	O
specimen	O
slides	O
or	O
to	O
a	O
1.25	O
telescope	O
eyepiece	O
.	O
</s>
<s>
Because	O
the	O
T-mount	B-Algorithm
lenses	O
have	O
a	O
long	O
flange	O
distance	O
of	O
55mm	O
and	O
most	O
35mm	O
cameras	O
have	O
shorter	O
flange	O
distances	O
,	O
a	O
simple	O
mechanical	O
adapter	O
called	O
T-Ring	B-Algorithm
is	O
needed	O
to	O
adapt	O
a	O
T-mount	B-Algorithm
lens	O
to	O
any	O
camera	O
body	O
without	O
optical	O
correction	O
to	O
achieve	O
its	O
closest	O
focus	O
distance	O
.	O
</s>
<s>
An	O
adapter	O
ring	O
has	O
a	O
female	O
M42×	O
0.75	O
metric	O
thread	O
on	O
one	O
side	O
and	O
a	O
corresponding	O
lens	B-Algorithm
mount	I-Algorithm
of	O
the	O
camera	O
body	O
on	O
the	O
other	O
side	O
.	O
</s>
<s>
A	O
T-adapter	O
consists	O
of	O
an	O
inner	O
ring	O
with	O
T-mount	B-Algorithm
thread	O
and	O
an	O
external	O
ring	O
with	O
corresponding	O
lens	B-Algorithm
mount	I-Algorithm
.	O
</s>
<s>
The	O
T-ring	B-Algorithm
and	O
the	O
T-2	O
ring	O
are	O
identical	O
to	O
each	O
other	O
.	O
</s>
<s>
Standard	O
T-rings	B-Algorithm
usually	O
have	O
the	O
same	O
external	O
diameter	O
of	O
their	O
inner	O
ring	O
because	O
some	O
T-mount	B-Algorithm
lenses	O
have	O
their	O
inner	O
ring	O
built	O
onto	O
the	O
flange	O
,	O
thus	O
the	O
external	O
ring	O
of	O
the	O
T-adapter	O
can	O
be	O
directly	O
attached	O
,	O
as	O
described	O
above	O
.	O
</s>
<s>
Since	O
some	O
DSLRs	O
wo	O
n't	O
meter	O
without	O
electronic	O
lens	O
data	O
,	O
some	O
adapters	O
are	O
now	O
sold	O
fitted	O
with	O
a	O
Dandelion	B-Algorithm
chip	I-Algorithm
which	O
can	O
be	O
programmed	O
to	O
identify	O
the	O
focal	O
length	O
and	O
aperture	O
limits	O
and	O
enable	O
metering	O
and	O
in	O
some	O
cases	O
focal	O
confirmation	O
.	O
</s>
<s>
The	O
thickness	O
of	O
the	O
external	O
ring	O
on	O
an	O
adapter	O
is	O
equal	O
to	O
the	O
difference	O
of	O
the	O
flange	O
distance	O
between	O
the	O
T-mount	B-Algorithm
and	O
the	O
corresponding	O
lens	B-Algorithm
mount	I-Algorithm
in	O
order	O
to	O
achieve	O
infinity	O
focus	O
.	O
</s>
<s>
They	O
can	O
be	O
attached	O
to	O
smaller	O
format	O
cameras	O
with	O
a	O
combination	O
of	O
corresponding	O
lens-to-T-mount-adapter	O
and	O
a	O
T-Ring	B-Algorithm
.	O
</s>
