Tips on Zone Focusing

[raid]

Actually, it is tips on why zone focusing can go wrong at times.
So I am using a Zeiss 45/2 in Contax G mount on an Olympus EP2, and I find myself in a position where zone focusing is needed.

What are the complications?
1. The lens has been modified to M mount.
2. An adapter is used. M mount to M4/3.
3. The lens was modified for closer focusing.

To make a story short, the true focus has little to do with the distance scale on this lens after all these factors. Setting the lens to cover infinity results in soft images when I expected tbe setting to cover infinity. I discovered this fact after one memory card ....


The moral of the story is to check these factors out before going on a trip.

 

[mfogiel]

For zone focusing a shorter fl would be recommended, as if you focus your Planar at 2 meters and at f22 you will only cover from 1.5 to 3 meters. On film you would get sharp images between 1,2 meters and 6 meters, while focusing at 3 meters you would have sharp images from 1,5 meters to infinity.
The idea would be to get a shorter lens, then all problems get solved very fast. With a 20mm lens you will cover from 120cm to infinity by focusing at 235cm with f11.
Another important point: you need to crank up the ISO, so that you shoot at least at 1/500, else you will risk blur with moving subjects.

 

[GaryLH]

Ok..Raid, what am I missing here? 🙁

Contax G is a pure af lens w/ manual aperture ring but no manual focusing scale or ring a for that matter. A Contax G to m43 adapter provides the focusing ring capability.. But I have never seen one that had a focusing scale.

Are we talking about the same lens? Are we talking about a contax g lens that has gone thru a complete lens conversion and thus is not really a contax g mount lens any longer?

So have u marked somewhere on the lens infinity focus point? W/o exact infinity mark, any scale/zone focusing scales one would place on the lens artificially would be off.

Gary

 

[raid]

Gary: This lens as been custom converted to M mount. It has a distance scale like a reguar M lens. I also have it in G mount. I took with me the M mount lens in case I wanted use it also on the M9.

Fogiel: I was not planning to use the 45mm lens with zone focusing. It just happened that I took some photos from the hip in one setting, and I was quickly taking photos from a harbor tour by boat in a crowd, so I needed to quickly snap some shots. The 45/2 did very well with manual focus in the rest of the images.

The higher ISO setting is useful. I know.

I have been using wide angle lenses with zone focus for many years. My CF 25/4 for example is a lens that s not RF coupled.

 

[burancap]

I was never that concerned with scales or hyper-accurate distances. I do a much dumbed down version of zone focusing and simply pick an object at a distance I'll be shooting. Focus, and go on my way.

 

[raid]

In my case, the deceptive part was a wrong ditance scale when used with the adapter.

 

[Monochrom]

What does it mean the lens was modified for close focusing?

adapters should keep optical elements distance to film plane as standard and retain the ability to focus up to infinite...
No matter what kind of contax to m mod or m to 43 adapter are involved.

The contax planar lens can reach down to 50cm that´s pretty close.

If the lens was mod to reach more than 50cm like a macro then won´t be able to focus beyond certain point and scale focusing will be messed up

Perhaps you may ask the person who did this mod or check the adapter´s info to check for this issues.

Good luck!

 

[batterytypehah!]

To infinity, and beyond!

Blame the adapter. I have two M4/3 adapters, admittedly the cheapest kind, that are both about 1mm too short. I believe this is intentional on the part of the manufacturers. It makes sure you can reach infinity focus without adjustment work at the factory. But, at the expense of close focus distance, and rendering the distance scale useless.

Mine are Pentax K (Fotga brand) and Konica AR (Fotasy). It's a simple matter to add some shims (washers) under the mount screws, but you need to add a "gasket" to keep the light out.

Oddly enough, my el-cheapo LTM to M4/3 adapter is spot on.

 

[raid]

Thanks for the comments. I can check things out by using this lens without any adapter on on M body. If focusing is correct there, then it is the adapter.

 

[waileong]

Wrong moral

Wrong moral

The moral should be, you dof marks on the lens are no longer good, because the effective focal length has increased.

Actually, it is tips on why zone focusing can go wrong at times.
So I am using a Zeiss 45/2 in Contax G mount on an Olympus EP2, and I find myself in a position where zone focusing is needed.

What are the complications?
1. The lens has been modified to M mount.
2. An adapter is used. M mount to M4/3.
3. The lens was modified for closer focusing.

To make a story short, the true focus has little to do with the distance scale on this lens after all these factors. Setting the lens to cover infinity results in soft images when I expected tbe setting to cover infinity. I discovered this fact after one memory card ....


The moral of the story is to check these factors out before going on a trip.

 

[raid]

I add your point then!
By the way, the lens focuses correctly on an M body. I just tried it out.
With the EP2, infinity is at 2.5 meters.

 

[Sparrow]

I was never that concerned with scales or hyper-accurate distances. I do a much dumbed down version of zone focusing and simply pick an object at a distance I'll be shooting. Focus, and go on my way.

... yep, that's my way too ... simples

 

[GaryLH]

Gary: This lens as been custom converted to M mount. It has a distance scale like a reguar M lens. I also have it in G mount. I took with me the M mount lens in case I wanted use it also on the M9..

I could be mistaken, but it sounds like the guys who did the conversion did not do a good job either w/ the distance scale itself or anchoring true infinity focus point of the scale or it could also be a by product of the close focus capability u mentioned...

Have u ever focused on something that is about 2-3 miles away w/ the Contax G lens and then check if the inf mark lines up correctly? The two most important calibrations as I understand it.. First is the inf mark and next is the close focus mark (this is procedure I remember reading about for adjusting focusing on scale focusing medium format folders that u have replaced or taken apart the lens of. The scale distance marks most also match the design of focusing helicoid (I believe, just guessing, i.e... A scale designed for a Leica rf 50 may not be accurate on a Konica rf 50).

Good luck
Gary

 

[GaryLH]

Thanks for the comments. I can check things out by using this lens without any adapter on on M body. If focusing is correct there, then it is the adapter.

Yep could also be the adapter. I forgot to mention the adapter. I was thinking u had the same problem both on your m and m43 cameras. I always check inf focus w/ any adapter I buy and shim them to infinity point. The cheaper the adapter, the bigger the machining tolerences are, in order to keep cost down...

Gary

 

[ZeissFan]

I think distance scales today on most lenses are not precise. They should be, but it seems that if you pick up three different cameras and focus on the same object that is between 5 and 15 feet from you, each lens will show a slightly different distance.

As far as not being able to focus at infinity, that sounds like an issue that could be traced to the number of lens adapters. And if each one is a bit loose with the tolerance and infinity, then you can really be off, especially when you factor in the 2X crop of the M4/3 format.

Personally, if I wanted to shoot a Planar, I would get a Rollei QBM 50mm Planar and one of the adapters for M4/3. The f/1.8 Planar is an outstanding lens, particularly the later HFT version. I wouldn't pay extra for the f/1.4 Planar.

 

[raid]

Mike: I use a QBM Planar on M 4/3 cameras with an adapter. It is awesome lens.

 

[raid]

Yep could also be the adapter. I forgot to mention the adapter. I was thinking u had the same problem both on your m and m43 cameras. I always check inf focus w/ any adapter I buy and shim them to infinity point. The cheaper the adapter, the bigger the machining tolerences are, in order to keep cost down...

Gary

Gary,

Your points are well taken. In my case, it seems to be the adapter.

 

[batterytypehah!]

The moral should be, you dof marks on the lens are no longer good, because the effective focal length has increased.

Not so. The DOF of a given focal length at a given aperture doesn't change. That's the whole crux with adapted legacy lenses on crop factor bodies. The FOV changes according to the crop factor, but the DOF remains the same. Which is why lenses that are fast for their FL are so sought after now.

As an example, if you put a 28mm lens on a Micro 4/3 body (crop factor of 2), it will act like a "normal" lens in terms of its FOV, equivalent to 56mm on 135 film. But it's still a 28mm lens with its really deep DOF, and blurring the background will be much harder than with a normal lens on film.

 

[raid]

Yes, this I know. The DOF does not change with m4/3. I made use of the shallow DOF at aperture 2.4 with the 45mm les. The OOF is quite pleasing.

 

[cpc]

Just shim the adapter. The problem is not in the change of FOV on a crop body. Your adapter is most likely too thin. I've seen only one adapter in my life which was perfect thickness out of the box, and I have dozens.

I use thin metal shims (sometimes layered) to fix my adapters so that the distance scale is correct. But you can use whatever material is around, just make sure it doesn't fall apart (paper is not a good idea).

Shim, test focus with a measuring tape, repeat until results are satisfactory. You will generally need 2-3 iterations.