Mamiya C220 50mm lens distortion

<p>Will be undertaking an architectural project in New York City before very long and want to use MF.<br /> Mostly, I'm concerned with keeping straight building lines straight, or, as close as I can come.<br /> Yes, I know, but 4X5 is just not going to happen.<br>

I've been researching lens distortion and understand that the MF SLR lenses exhibit edge distortion because of their 'retrofocus' construction that makes way for the mirror.<br>

I've also seen that MF rangefinders, because of their lens construction, minimize lens distortion to a significant degree, but I'm sure not completely.<br>

My question is, what kind of lens distortion should I expect from the 50mm Mamiya C220?<br /> I actually started with this camera more years ago than I care to count. It might be nice to go back to one.<br /> But not if the lens won't perform as I'd like.<br>

I've also been looking at some of the press camera options but want to get a sense on this C220 lens first.<br>

Thanks, Bob</p>

 

<p>Without a mirror to move out of the way I don't think any of the Mamiya TLR lenses would be retrofocus. Perhaps you could test the lens under various focusing distances. This is important because distortion can vary as a lens is focused. Also, don't rule out the MF SLR. Especially if 50mm on your C220 isn't wide enough. Again, test if you can. About those straight lines: while a well-corrected wide angle lens can minimize linear distortion, you must also watch out for keystoning (converging parallel lines). This occurs when pointing a camera up to take in all of a tall building. Only a view camera or a an expensive perspective control lens on MF can correct for that. For B&W images, though, you can tilt the easel and stop way down to correct for it if it is not too severe.</p>

<p>As far as I know there is no 50mm lens for the Mamiya C220. The nearest one should be the 55mmf4.5 which, at least for the example I use, shows no significant linear distortion. Because it is a non fisheye lens it will render parallel lines as converging when those lines are not parallel to the film plane. But that applies to all lenses; even pinholes!</p>

<p>I stand corrected and was referring to the 55mm on the C220. I also plan to shoot buildings from a higher vantage point to minimize how far up I have to aim the camera to eliminate keystoning and converging verticals.<br>

Another camera I am considering is the Mamiya 645 series. They have lenses as wide as 35mm and even a 50mm shift lens.<br>

I just wonder about the converging verticals on SLR lenses, even if the camera is essential level.<br>

Bob</p>

<p>Bob, your second post makes things clearer than your first. You are not talking about the optical aberration called distortion, but you're talking about convergence of the vertical lines.</p>

<p>To avoid convergence, you need to have the film plane parallel to the building you're shooting, which means the back of the camera is perpendicular to the ground. For cameras without movements, this means the camera is level. You can check this with a bubble level, or, if you can see the horizon, it will run through the middle of the frame.</p>

<p>If you have to tilt the camera upwards to get it all in, an easy solution may be to scan your negative and correct the convergence in Photoshop. If you're printing optically, it's also possible to correct convergence with some enlargers, but I've never done this myself.</p>

<p>The issue of retrofocus construction is not relevant to your question. The Mamiya 55/4.5 TLR lens is indeed retrofocus, and so are most wide and normal lenses for SLRs. Retrofocus lenses often render straight lines as a tiny bit curved (called 'barrel' distortion), but they won't make your verticals converge unless the camera is pointed up.</p>

<p>I think I'm getting tripped up, and tripping others, over my choice of words.<br /> If I shoot a scene with my 28mm (equivalent) wide angle EOS 18-55 lens, or most other conventional wide angles, even if the camera is PERFECTLY LEVEL (not shouting, just emphasis), any vertical building details at the edges are distorted, as if they are collapsing inward.<br>

But, I have seen some excellent rangefinder samples photos of wide angle shots where the edges are completely or nearly, straight, even wider than 28mm. <br /> Rectilinear or ASPH is a term I see most often applied to these kinds of lenses.<br>

This is the kind of 'distortion' I would like to minimize.<br>

Is that any better of an explanation?<br>

Bob</p>

<p>In other words, you are seeking to avoid or at least minimize barrel or pincushion distortion. This is more common with zooms. Wide angle primes, even retrofocus ones, can be corrected quite well these days so that distortion is minimized. Also, depending on lens design, distortion can vary with distance. Until the development of floating elements, lens distortion was tested at a specific focal length.</p>

<p>Thanks Mike and all,<br>

My research continues.<br>

Bob</p>

<p>Bob,<br>

If I understand you correctly you are talking about 'pincushion' distortion where straight lines at the edges of the frame seem to curve inwards. The converse is 'barrel' distortion. To find this information you would need to find some reviews of the lenses. Look up Graham Patterson on the web - he's an authority on Mamiya TLRs.<br>

I've just shot some interiors using a C220 but with the 80mm lens and they are fine. I can't think of any reason why a 55mm should not be fully corrected.</p>

<p>The 55/4.5 Mamiya TLR lens is a retrofocus design but is well corrected for distortion. there is definitely a mirror in the way, it's just in the way of the viewing lens. But the whole TLR design requires the two lenses to have the same length optical path to the ground glass and film so the taking lenses is the same distance, both mounted to the same front standard. Thus, the TLR design does not free you have needing retrofocus wide angles.<br>

The 65mm lens is long enough to clear and not require a retrofocus design.</p>

<p>I often shoot architectural jobs on a Mamiya 645 with a 35mm lens.<br>

This lens has some pronounced barrel distortion and, unless the camera is exactly level, there will be some convergence of vertical lines.<br>

But, because I shoot "Hybrid" (i.e. shooting film, scanning it on a Nikon Coolscan 9000, and doing all post processing in the digital domain) these distortions aren't much of a problem.<br>

Photoshop and other software packages have tools to correct both kinds of distortion.<br>

And, because I'm making these adjustments at full screen resolution, I can often be more precise than I could be even if I was working with a view camera.<br>

Here's an example:</p>

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