Help me understand: focusing an ultra-wide

[squirrel$$$bandit]

So I'm thinking of getting the 21mm Color Skopar for my Bessa. And I've read here and there people talking about how it's not really relevant that such a lens be rangefinder coupled (though I realize this one is).

I've never shot with a lens this wide, so let me see if I have this straight then--is it that the depth of field is inherently much deeper on a lens like this? So that, stopped down, it's always more or less in focus past a certain distance? Is there any kind of formula for a 21mm, like for instance what aperture corresponds to what minimum focus distance?

Let me know if I have this wrong. Also, I assume I should buy the LTM version of this lens, since I already have an adapter, and it comes with the viewfinder. There's no disadvantage, I assume, to doing this instead of getting the M mount?

 

[BillBingham2]

Optically from everything I have read and heard they are the same. The "Quality" of the mount on the newer one is more Leica like. Now for I had a 25/4 in the old mount style and the 40/1.4 which is new mount style. While the 40 felt more like my old 35/2 'Cron, there was NOTHING wrong with the 25s mount. It worked and felt great.

I had a 21/2.8 Elmarit that was coupled and the 25/4 LTM that was uncoupled. After about seven years with the 25/4 I think I got three or four shots that were out of focus. In hind sight with the 21, I should have used guess focusing more, I would have been faster. Yes, the effective DOF on 21 is very deep, especially starting at f4. What I did was guess.

I developed a system of learning three different points dead on. 1 Meter, 2 Meters and 3 Meters, beyond that it did not matter with the 25. Once you can tell where those points are every time you guess as to where in between your subject is and let DOF do the rest. If you know that you subject is between 2 and 3 meters, you set your focus to in between and you are fine. There are some Hyperfocal length charts that make this much easier. I never really used them myself but some folks here love them. They are easy and fun. When I was shoot outside I just set my infinity mark at say about where f13 would be (shooting at f16) and everything else I wanted was fine. I used the shutter speed to adjust exposure.

I would get a black LTM version as it will mount on more cameras and with the finder is quite a bargain these days. The finder allows you to use it say on a Bessa L you might pick up in the future or an old Leica IIIa. It's more versatile, but that is me.

B2 (;->

 

[Rafael]

If you play around with the DOF calculator (HERE), you'll get a sense of just how much depth of field you get with wide angle lenses.

 

[squirrel$$$bandit]

Black LTM is the plan. And this sounds reasonable to me--I'm accustomed to scale focusing my Robot (though not very good at it, as yet).

What do you mean, though, by "I just set my infinity mark at say about where f13 would be (shooting at f16)"?

 

[Nikon Bob]

I just looked at my LTM version of this lens and if you set hyperfocal for F8 the scale on the lens indicates acceptable focus from 3 feet to infinity. Somewhere in that range there is a exact point of focus, about 6 feet, near as I can tell with looking at the lens. There is virtually no reason to actually focus on an exact distance but I do so habitually.

Bob

 

[BillBingham2]

What do you mean, though, by "I just set my infinity mark at say about where f13 would be (shooting at f16)"?

Outside, shooting with the Sunny-16 rule (f16 and 1/filmspeed for your shutter speed) for the right exposure I just leave the f-stop at f16. Then I find a point on the right side of the lens between the f11 mark and the f16 mark. These marks on the rear of the lens are approximate guides for depth of field (DOF). So if you set your f-stop to f8, everything between the two f8 marks (one on the left for closer, one on the right for further) will be in focus. So what I do is set the f-stop to f16 and set the infinity mark between the f11 and f16 mark on the right side (a bit closer to the f11 mark). This gives me everything from infinity to pretty close with a 21 to be in focus without having to adjust anything. This is my modified use of the Hyperfocal distance focusing. In HFDF (not sure of the term?), you set your mark for infinity focus to the right f-stop mark you are exposing at and shot away without adjusting. I'm just a touched touched and want to make sure everything in infinity is sharp. Now in reality anything in infinity will be so small with a 21 or 25 that you could not tell on a 35mm frame of film.

B2 (;->

 

[Nikon Bob]

This link might help with setting hyper focal using the distance scale on the lens http://www.great-landscape-photography.com/hyperfocal.html .

Bob

 

[charjohncarter]

I have an auto focus 20mm Pentax lens. I finally just got an auto focus body for the 20mm and my auto focus 28mm. It is so much easier.