Ultra Wide Lens Question for Real Estate Photography

[Remo Nonaz]

I am shooting real estate listing photography for a local company. The camera I am using is a Panasonic G7. My go to lens for interior work is the Panasonic 7-14 lens. This lens has a 2x crop factor compared to a full frame camera. At 9mm the lens is shooting a field of view that is roughly 90 degrees wide.

The Panasonic 7-14 is very free from barrel distortion but I am concerned with the distortion that occurs at the outer part of a frame where objects appear wider than they are in real life – for example doors become wider, chairs get elongated and round objects like clocks become oval. The closer you are to the subject and the shorter the focal length, the worse this form of distortion becomes.

My question is: Is this type of distortion proportional in a crop sensor lens to a full frame lens? Or put another way, would a full frame image shot with an 18mm lens be exactly the same as 2x crop sensor image shot with a 9mm lens? Or would the full frame camera have an advantage in reducing the distortion?

[Slobodan Blagojevic]

...would the full frame camera have an advantage in reducing the distortion?

No.

The only way to reduce that type of distortion is to increase the distance from the object, use a less wide-angle lens, or position yourself parallel to the object.

[Remo Nonaz]

Thank you, Slobodan. You would be the right person to answer this question! I looked at the work on your web site (very nice!) and I can see the occasional example of the distortion I am concerned with creeping in, but in general you have it well under control. As noted in your response, controlling this problem is best handled by moving back and/or shooting with a longer lens length. Alas, shooting bathrooms and small bedrooms usually does not allow either correction to be used, so there is apparent distortion.

In all fairness to myself, my work is low cost real estate "content", not high budget magazine work. The customers get what they pay for. (And I get paid for what I do, LoL.) The Panasonic 7-14 is a good lens for this work and I find that I am usually shooting at 9mm. At that length the distortion is acceptable. When I can, I extend to 10mm or 11mm, and I avoid 7mm unless a stairway or small room dictates that I have to use it.

[kers]

The 'distortion' is nothing else than the consequence to project a 90/100 degrees or more image while keeping straight lines straight. (equitangular projection)
At some point is looks unnatural; the cylindrical projection can than be used but you will loose straight lines.

The only time i can accept a more than 90/100 degrees image is a  frontal symmetrical photograph; straight in front of a building for instance.

[bjanes]

The Panasonic 7-14 is very free from barrel distortion but I am concerned with the distortion that occurs at the outer part of a frame where objects appear wider than they are in real life – for example doors become wider, chairs get elongated and round objects like clocks become oval. The closer you are to the subject and the shorter the focal length, the worse this form of distortion becomes.

You are dealing with volume anamorphosis, which is not a lens aberration but rather a perspective effect encountered with wide angle lenses. It can be corrected with a US$ 79 program by DXO: Viewpoint 2. Here is a review.

Bill

[Bart_van_der_Wolf]

You are dealing with volume anamorphosis, which is not a lens aberration but rather a perspective effect encountered with wide angle lenses.

Bill is correct, in fact all lenses produce a certain degree of projection distortion when the image is projected on to a flat plane, and is viewed from the wrong perspective position.

With Wide-angle lenses, the required (for distortionless) viewing position of the output is uncomfortably close, and we therefore look at the output from too far way, and hence we experience a distorted (stretched towards the edges/corners) view. For telelenses we usually view the output from too close because the distortionless perspective viewing position is too far away from the output. When we view our telelens output from too close a distance, we experience a compression of the perspective.

It can be corrected with a US$ 79 program by DXO: Viewpoint 2. Here is a review.

Yes, or with a pano-stitching program that allows some control over the chosen output projection, such as PTGUI (or the free Hugin). However, that only works for some image content, mostly 3D objects (like people) without straight lines because those lines will get warped by corrections for the perceived wide-angle stretching. The panoramic rectilinear projection is the same as the optical projection on a flat (sensor) plane, but some projection methods can distort but still keep diagonal lines straight, others keep only vertical lines straight, but typical interiors can have many straight lines in various directions/angles, and any correction will warp some or all of them.

It's a compromise that needs to be sought to compensate for the wrong viewing distance perspective. Shooting from a longer distance (if possible) will allow to get a normal output viewing perspective from a normal viewing distance.

The math is simple, to get a perceptually undistorted view of a 36 x 24 cm output from a 36 x 24 mm sensor, at say 30 cm or 12 inch viewing distance, one should use a focal length of 1/10th of the viewing distance (30 mm or thereabout). Everything (sensor vs output dimensions, and focal length vs. viewing distance) scales proportionally for different sized output or viewing distances.

If the required focal length is shorter to achieve the desired FOV, one should either print larger or view from a closer distance.

Cheers,
Bart

[Slobodan Blagojevic]

... my work is low cost real estate "content", not high budget magazine work...

You are right about that distinction between RE and architectural/editorial photography. In RE photography forums, the mantra apparently is "the wider, the better." And I mean "super wide" means there not 16mm, but 10mm or 12mm. Some RE photographers swear that their clients (RE agents) love it and demand it, to the point of losing gigs if they can not provide it wider than the competition.

I assume the rationale (of the RE agents) is that it makes the space appear larger. However, given the trend toward ever-larger McMansions in the last several decades, "larger" often appears as "emptier." The space loses it's potential cozy feel. And then, of course, there is that totally unnatural geometric distortion.

Architectural/editorial photographers go instead for a preservation or demonstration of the space's essence. They select a narrower angle of view, but include the elements that will present the spirit of the space, as the architect or interior designer intended. My instructor at an architectural workshop, himself one of the best in the field, called that desire to show as much as possible in one shot a "wide-angle abuse." Which reminded me of the difference between pornography and erotica: it is often better to leave things hinting, suggesting, implying, unsaid and unseen, yet palpably present, rather than exposing it all.

There is a little optical trick one can sometimes use to minimize the sense of distortion. Very often a slight repositioning of the elements of the scene might "correct" the distortion. For example, in the shot below (working examples, just meant to illustrate the point), a slight twist of the chair creates less distortion. Again, these are not perfect examples, just something I had on my hard drive at the moment, but you can get the idea. These were crops from a 16mm lens, in my "RE mode."

[Remo Nonaz]

As noted, I try to start with 9mm (18mm full frame) and then zoom in or out as the scene and shooting distance allow. So far this seems to work pretty well - I don't have many shots that are grossly over wide and no one has complained I'm not wide enough yet. My original concern was that by using the shorter micro four thirds lenses, even with the same shooting angles, the equitangular projection distortion might be exaggerated. But, it seems that is not an issue, it's just a fact of physics and I have to deal with it.

[pixjohn]

I shoot with wide angle lens and deal with all the time. One way to correct this look, is to use a longer lens and stitch. I personally don't use that technique, but it works.

[Slobodan Blagojevic]

... One way to correct this look, is to use a longer lens and stitch. I personally don't use that technique, but it works.

Sorry, it doesn't.

What causes the said distortion is the distance from the subject, not focal length. Stitching increases horizontal (or vertical) field of view, but it doesn't effect the distance from the subject.

[georgem]

No.

The only way to reduce that type of distortion is to increase the distance from the object, use a less wide-angle lens, or position yourself parallel to the object.

So, this means that using a 9mm lens on m4/3 will give the same distortion -of that type- as a 120mm lens on 8x10 (both 18mm equiv.)?

Or would you have to move much farther back, in order to capture the same scene with the 8x10, effectively reducing distortion?

Sorry, it doesn't.

What causes the said distortion is the distance from the subject, not focal length. Stitching increases horizontal (or vertical) field of view, but it doesn't effect the distance from the subject.

I don't doubt this, but then I remember this thread on FM from a few years ago http://www.fredmiranda.com/forum/topic/713806/0&year=2008#6484999. Please manually load the image referenced in the second post, as it won't load otherwise. He seems to argue and demonstrate that stitching produces less distortion.

[Slobodan Blagojevic]

I didn't check your calculation, but if it is correct that 120mm and 9mm have the same horizontal field of view, the distortion we talk about should be the same.

As for the FM thread, if you are referring to the post #11's kitchen photo examples, they are simply not done well. The standpoint is not the same (higher for the non-stitched image), the field of view is a bit wider in the non-stitched image, but most importantly, the camera is not leveled, i.e., vertical, as it is in the stitched image.

[Cornfield]

Distortion and perspective are being confused in this thread.

I consider distortion to be when a straight edge in the scene is not straight but has curvature caused by a wide lens.  The distance between camera and subject governs perspective not the lens.

[David Eichler]

Distortion and perspective are being confused in this thread.

I consider distortion to be when a straight edge in the scene is not straight but has curvature caused by a wide lens.  The distance between camera and subject governs perspective not the lens.

With wideangle lenses, you are potentially dealing with at least four types of distortion: rectilinear, scale, perspective (converging lines that are parallel in real life) and volume anamorphosis (the stretching effect at the edges).

[Ellis Vener]

No.

The only way to reduce that type of distortion is to increase the distance from the object, use a less wide-angle lens, or position yourself parallel to the object.

Or change where you stand.