Leitz Fokos rangefinder mini review
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| Leitz Fokos rangefinder. |
Use of rangefinders today
With auto-focus and digital live view capable cameras the traditional optical rangefinder has gone out of fashion. For the landscape photographer which wants good control of the depth of field (DoF) it's however still valuable to be able to measure the distance to an object. (My landscape photography focusing article describes how to work with depth of field.)In the digital medium fomat world live view is still rudimentary, and the technical cameras are 100% manual and thus lacks auto-focus. Here one either focuses using the traditional ground glass with a loupe (view camera), or has a camera with a very detailed distance scale on the focusing ring and use a rangefinder to find which distance to dial in. In this case when rangefinding is used for focusing images with up to 60-80 megapixels (the resolution of current high-end digital backs) many desire a very high focusing precision, and the natural choice for this is a laser distance meter with outdoor capability like the Leica Disto D5. Some complement it with a long distance rangefinder (designed for hunting) to cover longer distances.
However, these laser units are expensive, relatively bulky and use batteries. If you focus using live view or ground glass and only need rangefinding for making DoF judgements now and then, carrying a laser distance meter may be overkill. I thought so and therefore decided to get a vintage rangefinder instead. While these rangefinders are not as precise as a laser distance meter it's still much better than the typical DSLR lens distance scale (which is next to unusable).
For those that haven't used an optical rangefinder before: what you see when you look through it is a main pass-through image and a semi-transparent image layered on top. When you turn the wheel the semi-transparent image moves sideways and when it's perfectly aligned on top of the main image you have found the range, and you read it off the distance scale on the wheel.
The Leitz Fokos
One of the real classics is the Leitz Fokos rangefinder. These where manufactured 1933 to 1966 and intended to be mounted on a Leica camera. Today these are quite easily obtained in the second hand market. While much cheaper than a high quality laser distance meter they can still be quite expensive as they are collectible. There are other rangefinders that provide better value, but at the time of writing the Leitz Fokos is the only one I've tested.Other brands/models to look for: Fotoman, Voigtländer, Watameter, Medis, Amsco DeJur, Photopia, Kodak (there are many more). Fotoman is the only brand I know of whose rangefinder still can be bought new. The Amsco DeJur is very similar to the Leitz Fokos. Few rangefinders of this type has as detailed distance scale and long maximum distance before infinity (50m) as the Fokos.
It's available in feet or meter distance scale, the one I use is in meters (in the second hand market it's generally easier to find rangefinders with feet scale). It's 7.5 cm long, all metal and weighs 60 grams, compared to any laser distance meter it's small and light. For the size it's heavy though which gives it a really solid quality feel, rare to find in modern photography equipment. I also like the retro appearance.
Accuracy
By aiming a laser pointer through the rangefinder I could test the accuracy without factoring in my eyesight and skill. Just turn the wheel until the two red dots from the laser become one. The scale starts at 0.75m, and up to 2 meters one can generally say that it is within +/- 1-2 cm, which was actually better than I expected. At longer ranges it became too difficult to test accuracy this way, so then I used it normally; I measured the distance first with a laser distance meter and then compared with the result I got from the range finder, thus factoring in my skill and eyesight.There are a few factors that affect accuracy of a rangefinder of this type:
- Mechanical accuracy of the instrument.
- The resolution of the distance scale (ie which distances you can read off the scale).
- Your eyesight, skill, and contrast of focusing target.
The distance scale has the following entries: 0.75m, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.7, 2, 2.5, 3, 4, 5, 6, 7, 10, 20, 50, and infinity. For modern use I think it's a little coarse, but we can improve it; as our eyes are very good at spotting a position exactly centered between two dashes on the scale we can calculate the corresponding distances with simple trigonometry and get a more detailed scale scale. Then the full scale becomes (calculated "inbetweeners" in italic): 0.75m, 0.77, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.6, 1.7, 1.8, 2, 2.2, 2.5, 2.7, 3, 3.4, 4, 4.4, 5, 5.5, 6, 6.5, 7, 8.2, 10, 13, 20, 30, 50, 100 and infinity.
As we can see the scale dashes are placed such that the inbetweeners are most often simply (a+b)/2 when rounded, sometimes a bit less though. I've memorized 8.2, 13and 30, and approximate the rest just as (a+b)/2, and with that you have a pretty high-resolved scale to work with. As a comparison, a Canon TS-E 24mm manual lens has the following distance scale on it: 0.21, 0.25, 0.4, 0.5, 0.7, 1, 3 and infinity, and that without dashes to line up - not usable.
With a laser distance meter you get the exact range on the millimeter, while on this rangefinder your readings will be of the type "a bit more than 5 meters but less than 5.5" rather than an exact number. I'll return to how useful those approximate readings are. The distance scale becomes coarser with longer distances, but as the depth of field grows accordingly DoF placement precision will be about the same over the whole scale, ie less precise plane of focus placement is masked by a deeper depth of field.
Going further on accuracy we then have the eyesight and skill factor. The rangefinder has no magnifying optics so you don't see sharper through the rangefinder than you do without it. If you have glasses be sure to look through them. Then there's the contrast of the focusing target, a sharp edge, as corner of a window on a building is much easier to focus at than a smooth rock. I'd say that in most scenes you'll find enough contrast, but there may be times when it's difficult so it's not fool proof.
I made a test focusing at 7 meters on a fairly high contrast subject, and with 10 repeats I managed to hit within a dash-width on the scale all times, which roughly means +/-15cm or +/-2%. I'd say that this or slightly better can be expected at distances up to 7 meters. With increasing distances it becomes less precise though. The reduced precision is possibly not due to the mechanical or scale accuracy, but to eyesight and skill. I'm near-sighted and I see a bit less good at distances even with glasses. When testing a target at 40 meters, I most often ended up at 50 or slightly above. Differing between say 40 and 60 meters is thus very hard for me based on the scale only. I'd say that for me the "safe" range is up to 20 meters, above that a naked eye distance estimation is often as good or better (using the rangefinder as support for distance estimation can still be useful). I would guess that if you have perfect vision you may get safe readings up to 50. However, I had a friend with better vision than me to try out which constantly got sligthly long readings on the 40m test target, so maybe the 50m mark is a little off? It seems consistent though, so if you have good eyes you can probably make safe readings up to 50.
When getting this type of rangefinder I would always recommend to compare your results with a laser distance finder so you know how precise it is. Some of them can be user-calibrated, the Fokos is not as easy (as far as I know). Mine is not off in calibration though, but as said possibly the scale wheel is not perfect for the 50 mark, it seems to be closer to 40.
Use in landscape photography
So what do a landscape photographer need, assuming we focus using live view? A typical rangefinder application would then be to measure the range to the closest object in the composition, look up that distance in a hyperfocal table (or use a DoF app) and then find a suitable focusing target near the resulting hyperfocal distance. In this case you would use deep DoF, and then you'd be interested in the range 3 to 6 meters for wide angles at optimal aperture (about 24mm f/8 in 135 terms), 6 to 15 meters for moderate wides (about 35mm in 135 terms), 15-30 meters for normal lenses. So as a tool for hyperfocal focusing of wide to normal lenses it works, but not really for tele lenses.You don't always need sharpness at infinity (it may not be visible), and in those cases you may use the rangefinder to measure the close and far edge, and use a DoF table to find suitable focus distance, and use the rangefinder again to find a target approximately at that distance.
This process may seem rather approximate, for example you rarely have an object at the exact focus distance you want, but as the close DoF edge distance grows very slowly with focus distance (and the far edge very fast) it works well in practical photography, at least for deep DoFs (ie smaller shooting apertures). This property also reduces the rangefinder accuracy requirement, and makes the relatively coarse distance scale of the Leitz Fokos to be of adequate resolution (although I recommend to learn the "inbetweeners"). Keep in mind that what you typically do if you don't have a rangefinder or tables is that you base everything on experience and estimates. The rangefinder + DoF table/app process will lift it to the next level to better support sharp image making with modern high resolution cameras.
To quantify I'd say that in 135 terms for f/8 and smaller apertures and focal lengths of about 50mm or shorter the rangefinder together with DoF tables is an adequate tool, while you for shorter DoFs will probably prefer other methods. In digital medium format terms that would be about f/11 and 75mm. With some training you can extrapolate with estimations to work out longer distances good enough for DoF judgements.
As the definition of the DoF edge is generally quite loose, ie if your circle of confusion is 10 or 15um does not matter that much, DoF can be handled quite approximatively and therefore this combination of rangefinder and tables (or DoF app) is successful. The original use of a rangefinder was for actual focus placement though; you found out the distance with the rangefinder and dialed in the same distance on the lens distance scale. I don't use it for that, instead I focus using live view on the DSLR and ground glass (with loupe) on the view camera. Live view is certainly more precise thanks to the magnification, and while I guess the rangefinder is competitive with ground glass on closer range it's not on longer range and since you cannot get an exact reading off the scale anyway the ground glass will win every time. Additionally, the DSLR has too poor distance scale on the lenses, and the view camera has no distance scale at all so you cannot dial in a distance even if you would know it on the millimeter.
If I would have say an Alpa with high resolution focusing ring and a high resolution digital back I still would not like to use the rangefinder for focusing. While it would be adequate in many hyperfocal scenarios where you don't need to focus on anything in particular you typically quite often come across scenes when you do want to have the focus at some specific point (and the DoF edges are less important), and then a higher focus placement precision is a desirable property. A laser distance meter is the obvious choice for this.
I keep the Leitz Fokos in my camera bag and use it from time to time to make DoF judgements. In most cases I can do distance by experience or use tilt focusing or other focusing techniques that do not require range finding, but in some occassions the rangefinder becomes useful. As I only use it for DoF judgements (rather than focusing) I don't need absolute precision, and therefore I find to be a more suitable tool to carry around than a laser distance meter, as it's very small and light and requires no batteries. I shall also confess that I'm attracted by fine all-mechanical instruments.
It would have been better if I could get reliable readings up to 100 meters rather than 20-30, but these small vintage camera rangefinders does not come in that configuration, most have their last scale mark at 20 meters (rather than 50 as Fokos has). If I had to get a considerably bulkier rangefinder to get reliable 100m readings I would still choose the small Fokos though, it's not worth that much having that extra range. Extrapolating with estimates works quite well, ie if you with the rangefinder measures that object A is at 40 meters you can quite accurately in the same scene estimate with the naked eye how far away 80 meters is.