[Leica] Noctilux vs 75 Summilux DOF

[Jim Brick <jimbrick@photoaccess.com>]

Bob,

You should never buy a 75/1.4 Summilux because it has LESS depth of field,
wide open, focused at the same distance as the Noctilux (also wide open). I
do not have any problem getting an extremely sharp plane of focus with the
75 at f/1.4 . Just because the Noctilux is f/1.0 doesn't mean that DOF is
non existent. And, as I said, there's more of it than with the 75 at f/1.4

Focus a Noctilux at f/1.0, at 2 meters and the DOF is 1.96m to 2.04m (.08m)
Focus a 75 Summilux at f/1.4, at 2 meters and the DOF is 1.98m to 2.02m (.04m)

And it gets worse.

Against the close focus stop, 1.0m for the Noctilux and .75m for the 75
Summilux, the DOF calculates to:

Noctilux .99 to 1.01 meter (.02m)
75 Summilux  .75m to .75m (.00m)

So if you would have trouble with the Noctilux, you would have more trouble
with the 75 Summilux.

Of course the image size with the 75 is larger which is why the DOF is
less. But the whole exercise here is to show that the 75 Summilux exhibits
less DOF than the Noctilux.

Jim



At 11:27 AM 2/3/00 -0500, BOB KRAMER wrote:
>	[BOB KRAMER]  Ha!  That's a good one, John!  And serves to
>illustrate one of the problems I have with the Noctilux (the going without
>food to afford it being another <g> ).  Not to mention that I have yet to
>see a sharp image... er... excuse me... yet to see a sharp *photo* :-) taken
>with this lens.  The plane of focus appears to be non existent!  Using this
>lens wide open, the question isn't "Do I want the eyelashes to be in
>focus?", it is "*Which* eyelash do I want to be in focus?".  Combine this
>problem with the high lens cost, the inevitable even if minor optical
>compromises that result with this fast a lens, and the lens size and weight,
>and I just don't feel a burning desire to own it.
>
>	I guess the Summilux appeals to me because I have been shooting with
>a 1.4 50mm since I bought a Canon F1 back in 1972, and have become very
>comfortable with this speed of lens.  Enough DOF to work with and enough
>speed to get the shot the lion's share of the time.  Besides, I still need
>21/24mm, 35mm, and 90mm lenses since the 50mm focal length is all I have
>right now for my Leica.  Not to mention that good user M4 and/or M5 I am
>lusting for.
>
>	Bob Kramer