Adapting a film viewfinder to R-D1?

[jimbobuk]

I've got the 15mm VL with its film based viewer for the hotshoe.

I'm wondering if anyone has perfected a technique of masking off the eyepiece so that its clearer where the R-D1 range lines.. I was thinking some kind of transparent plastic that is normally say an LCD protector.. could be placed onto the eyepiece in the shape of the R-D1 crop.. additionally it could be shaded with some pen to make it clear when viewing where the cropped area lies.

Has anyone had any sucess with this or is it not possible? The price for a digital equivelant viewer really does hurt a bit, so i'm keen to try it on the cheap for now.

Cheers

Jim

 

[RML]

Never tried it, but I've been thinking about it. I'm in the market for a 15mm and I'm wondering how to deal with the crop factor. I fortunately have a 25mm VF already, which I plan on using. I'd say, try out your idea and let us know how well it works!

 

[JoshRoot]

Some people use tape, some use a marker, some use something else. I use a 21mm VF, though a 25mm one is just as close.

 

[rvaubel]

I use the 25mm full frame finder with the 15mm heliar on the R-D1. Its too wide but I've learned to compansate. The 21mm might be a little tight but I don't have one and am not going to buy one to find out.
Does anyone know what the difference is with the finders that are dedicated to the R-D1? Are they just re-marked existing finders or are they actually manufacted to account for the 1.5 crop factor of the R-D1?
thanks
Rex

 

[jlw]

I use the 25mm full frame finder with the 15mm heliar on the R-D1. Its too wide but I've learned to compansate. The 21mm might be a little tight but I don't have one and am not going to buy one to find out.
Does anyone know what the difference is with the finders that are dedicated to the R-D1? Are they just re-marked existing finders or are they actually manufacted to account for the 1.5 crop factor of the R-D1?
thanks
Rex

All I can do is speculate, since I own only one of these Voigtlander "D" finders (for the 21mm lens) and don't have any other C-V finders against which to compare it.

But it looks to me as if they use the same optics as their nearest corresponding 35mm finder, with the frameline set for the R-D 1's coverage area.

For example, applying the R-D 1's 1.53x "crop factor" to a 21mm lens gives 32.13mm; so, I suspect my 21D finder has the same optics as a finder made for using a 28mm lens on a 35mm-format camera, but with a slightly smaller frameline to match it to the R-D 1.

Remember that you can't expect an auxiliary finder to match the lens' view field exactly anyway; finder designers have to provide a safety factor by making the finder so it always "sees" a bit less than the lens. That way, when framing a shot, you can be sure that what you see through the finder will show up in the picture (plus a little extra around the edges, which you can crop out.)

You certainly wouldn't want it the other way around, with the finder seeing more than the lens. If that were the case, you might compose a picture with an important element all the way out at the edge, then find it was completely missing from the final image!

Just to make the designer's task a bit more difficult, it's an optical fact that any conventional lens' effective focal length increases as you focus closer. So, if the finder were designed to exactly match the lens' field at infinity, it would show too much at close distances (where the lens' focal length increases a bit, tightening its angle of view.)

Instead, the designer has to set the finder so that the lens view shows slightly more than the finder view at closest distance; as a result, when you focus at infinity (where the lens' effective focal length becomes shorter) then lens will show quite a bit more than you saw through the finder. This may make it appear that the finder is designed very inaccurately, but that isn't necessarily the case; it's just that you need a large safety factor at infinity to make sure there's still enough when you focus close. (This is why the R-D 1's built-in finder frames show only 85% of the picture area at infinity.)

In my very crude tests of the 21D finder, I'd say its frameline is quite accurately matched to the R-D 1. When I use a 21mm lens at a close distance, such as 1m, the final picture shows just slightly more than I saw through the finder. At longer distances, the final picture will show more "extra" area, because of the factors mentioned above, but that's par for the course with any accessory finder.


[Yes, in case there are any punctilious camera historians out there, I know that a few rangefinder cameras incorporated "field size correction" in their finder framelines, so that the finder framed more tightly at close distances to compensate for the increase in the lens' effective focal length. The Konica Pearl IV and the Zeiss-Ikon rangefinder on the Polaroid 180 are two examples. But I don't think this feature has ever been designed into an accessory viewfinder -- although many variable finders, such as the Tewe, have a second index mark for use at close distances that "zooms in" the finder a bit tighter.)

 

[rvaubel]

Coming from a background of SLR , I have always framed fairly "tight".
My first rangefinder pictures (Bessas, starting a couple years ago) suffered from some framing error. I soon learned to frame more loosely. However, with the R-D1, because of the instant feedback, I decided to determine the exact field of view of the framelines vs. the sensor. The only lens I've tested so far is the 40mm Norton. I put tape up on the wall until the framelines were just covered (31 degrees by high school trig) . The 35mm framelines were just about perfect , the sensor capturing just a little more than the framelines.
I am contenplating getting a 28mm lens, either the Leica F2.0 ($$$) or the probable Nokton F1.9 My dilemma is which finder, if any, would work for an effective focal length of 43mm?
I don't think I'm the first on to have this problem.... but there does seem to be a finder gap.
Anyone have a suggestion?
Rex

 

[RML]

So, how "inaccurate" would the 25mm VF be when used with the CV 15/4? Would there really be a huge mismatch between the VF's VoF and what will end up in the shot itself? I'm asking because I have the 25mm VF and want to get the CV 15/4 but would prefer not to have to pay for an additional VF as well.

 

[RML]

Rex, the R-D1 has framelines for the 28mm, doesn't it? Seems you thus don't need an extra VF for the 28mm lens.

Or am I misunderstanding your question?

 

[Jim Watts]

So, how "inaccurate" would the 25mm VF be when used with the CV 15/4? Would there really be a huge mismatch between the VF's VoF and what will end up in the shot itself? I'm asking because I have the 25mm VF and want to get the CV 15/4 but would prefer not to have to pay for an additional VF as well.

I have used my VC 25mm finder with my friends VC 15mm a few times and from memory its a pretty good match for the 23mm equivalent of this lens on the R-D1.

 

[RML]

Thanks, Jim!

 

[jlw]

The only lens I've tested so far is the 40mm Norton. I put tape up on the wall until the framelines were just covered (31 degrees by high school trig) . The 35mm framelines were just about perfect , the sensor capturing just a little more than the framelines.

This is similar to what I've found using the 40/1.4 on an R-D 1. BUT... the sensor captures more than the 35mm framelines ONLY down to a distance of about 8 to 10 feet. Once you get closer than that, the lens' effective focal length has increased enough that you'll see more inside the framelines than you'll get in the image... not a major problem, as long as you're aware of it.

I am contenplating getting a 28mm lens, either the Leica F2.0 ($$$) or the probable Nokton F1.9. My dilemma is which finder, if any, would work for an effective focal length of 43mm?

I've got the 28/1.9 C-V and it works fine with the 28mm frameline that's built into the R-D 1. The numbers on the finder's frameline selector refer to that focal length of lens when used on the R-D 1 -- the sensor's "crop factor" is already accounted for in the positioning of the framelines.

If you want to use an accessory finder anyway (possibly because the 28mm framelines are hard to see for some eyeglasses wearers) here's a simple formula I've used to figure out the best match:

(lens focal length * 1.53 R-D 1 crop factor) / 0.85 [the 0.85 provides the same "safety margin" designed into the built-in finder.]

In the case of a 28mm lens, this works out to:

28 * 1.53 = 42.84... 42.84 / 0.85 = 50.4

So if you can find a 50mm viewfinder -- C-V makes one that you can buy from our advertisers for about $130 -- that would be your best match assuming you want to preserve the built-in finder's 85% safety factor. If you'd prefer a finder that more closely matches the lens' actual field of view, you can use a 40mm viewfinder (also made by C-V) -- but be aware that you'll be getting LESS in the image than you see through the finder.

 

[rvaubel]

RML
A quick test of the coverage of the VC 25mm viewfinder (with framelines, there are 2 versions) vs the 15mm Heliar.
Moving my trusty masking tape along the wall, I get apparent coverage of 160" horizontal X 126" from the wall. Trig tells us this is 65 degrees.
The actual coverage is 200" or 77degrees. This is born out in fact as I have to be careful to remember that the sensor will include a lot more than indicated in the finder. In fact , I think the 21mm finder might be a better choice. Josh, if your listening, waddaya say?
Rex