[Leica] Review of Jupiter-8 50mm f/2 lens.

["Richard Urmonas" <rurmonas@senet.com.au>]

I was interested in the Jupiter lenses after positive comments form the LUG.  I managed to obtain a lens.
What follows is my evaluation of this lens.  I should state that I have no optical background, and this
test was done for my own information.  Some of the tests will therefore the fairly simplistic.
I have no connection with either Leitz or the Jupiter lens people, their agents etc. etc.

The lens was tested by comparison to my Red Scale Elmar 50 f/3.5.  Both lenses were used on my
Leica IIIc.  The lenses were alternated i.e. Shoot test shot with Elmar, swap lenses, shoot test shot
with Jupiter at same shutter / aperature setting.  Go to next test shot.  All tests were done on a tripod.
Exposure set with a Gossen lightmeter using incident readings.

The Lenses:
Jupiter-8 50mm f/2, metal mount, suspected to originate 1970's.
Elmar 50mm f/3.5, "red scale" 1954.

Camera:
Leica IIIc 1942.  In good working order, regularly CLA'd.

Film:
Agfa CTx100 slide film.

Test 1:  A flare and contrast test.  A night street scene.  A sodium vapour street light was deliberately place
in the to left corner of the shot.  The sodium vapour lamp gives an orange light, so flare etc. can be readily
identified.

The result.  The Jupiter lens has more local flare than the Elmar at the equivalent stop.  At f/2 this is
severe.  The Jupiter also shows a strong aperature ghost image at all aperatures.  This is quite large, at
f/4 it is about 1/3 of frame height.  There was some all over contrast reduction in the Elmar at f/3.5
(i.e. shadows showed a slight amount of orange), this was diminished at f/5.6 and not noticable at f/8.
The Jupiter showed far more of this effect. It was present even at small aperatures, but with diminished
intensity.

Test 2: Photograph a sheet of newspaper fixed to the wall.  Good light.  This test permits resolution
and contrast to be evaluated.  Pincussion and Barrel distortion can also be tested.

The results.  The Jupiter is very sharp.  It is sharper than the Elmar at f/4.  At f/5.6 the difference is small.
At f/8 and below no difference was ascertained.  At f/2 the Jupiter has very poor contrast.  The
newsprint was a gray colour instead of black.  At f/2.8 this was improved. At f/4 and below the problem was
not discernable.  In the test the newspaper was fixed to a brown wall.  A section of wall was left visible
around all eadges so that barrel or pincussion effects could be seen.  There was no detectable distortion
in either lens.  A problem did surface with the Jupiter.  Because the shots were alternated I realised that
the Elmar shots showed a white paper, the Jupiter had a slight brownish colouration to the paper.
This could only have come from the wall and indicates some broad flaring effect.  It was present at
all aperatures.

Test 3:  Some "typical" photographs were taken.  This was to evaluate performance under "normal"
situations.

Results:  Both lenses show pleasing transitions from in-focus to out-of-focus.  The out of focus details
were pleasing with both lenses.  The Jupiter showed poor contrast in shots where a fair amount of
sky was present.  In detail shots under low contrast situations the Jupiter performed well and the images
were equally pleasing to the Elmar shots.  Knowing that the Jupiter had lower contrast the slide taken
with the Jupiter could be picked every time.

Conclusion:
The Jupiter is a sharp lens which delivers excellent value for money.  It does however suffer from contrast
and flare problems.  I suspect that the supression of internal reflections is poor.  I have sold the Jupiter.
Its performance for my applications (low light) was not up to my requirements.  For applications where the
flare / contrast issue is not a problem the the Jupiter will deliver sharp pleasant images at a bargain
basement price.


Richard Urmonas
rurmonas@senet.com.au