when should horizontal correction be used

[Steve M Hostetter]

Camera position was to left of bldg and lens was shifted right in attempt to show depth and keep facade from running down hill,,,, I'd really like to hear your opinions and or examples thx

[Alan Rabe]

Shift will only move the object back and forth in the focal plane. To correct your "running downhill" you need to use swing. Either front or back will do the trick.

[Vaughn]

I don't have a copy in front of me, but I remember an example in AA's The Camera where he used front shift to keep himself and his camera's reflection out of a store window, yet still keep the building's image centered on the negative. Using front shift he was able to set up the camera a little off center and not have his reflection in the window.

If one's camera did not have any shifts, but had front and back swing, one can accomplish the same thing by standing a little off center, pointing the camera at the center of the building, then swinging both front and back parallel to the front of the building. 

Shift (and rise/fall) are nice to use if one has the camera set up just right, but would like to include/exclude on an edge without moving the whole camera, which might otherwise might affect perspective or focus.

Vaughn

[Steve M Hostetter]

Hello,, I understand what Vaughn is saying ,,, a camera without side shift needs both standards to swing to accomplish the same effect as a side shift ... I believe this is what Alan is refering to

So to correct verical convergents you need to shift verticlly and to correct horizontal convergents you need to shift to the side in the direction where the lines converge..

My thoughts have always been that in architectual photography most architects will ask for both to be correct 99.9% of the time..

So the example that AA gives will not only remove his reflection but will also straighten the sideway converging lines as well, hence a level looking window..

Thats not to say that the example of the General Store needs this application and my gut feeling was that the shed roof here may look a bit abnormal as a result.

Others may not agree...?

[aduncanson]

Steve,

It seems to me that you are making this more complicated than it is. To prevent horizontal or vertical convergence just be sure to keep the film plane parallel to the principal subject plane. Then use rise or fall & shift, to compose your picture in the frame; or as Vaughn said, point the camera at the subject and apply swings & tilts to restore the film to parallel to the subject (and hope that your lens doesn't run out of coverage.)

I took a scale to your image and it looks to me like you managed horizontal & vertical convergence pretty well. The very top of the facade seems to run down hill at the right side, but most other lines seem parallel to the edges of the frame. It might just be that you would need a fun house mirror to make that old building look perfectly square.

[Vaughn]

Thats not to say that the example of the General Store needs this application and my gut feeling was that the shed roof here may look a bit abnormal as a result.

Yes, the roof over the pumps, etc. looks quite abnormal. My guess is that it looks so because of two reasons.

The first is the wide angle lens (for the format) used, and the second is that the image was taken at an angle to the building.

The roof is about the same width as the building, but because of the wide angle lens used, its leading edge is optically almost half again wider than the rest of the building. And because the camera is located to the left of the building, this extra length is tossed to the right. If the camera had been located in a centered position, relative to the building's front, the distorted width of the leading edge of the roof would have been evenly distributed to both sides of the building -- and the use of the wide angle lens would have been intuitively accepted.

But the camera angle has made the distortion of the size relationships almost painfully obvious. No amount of shift or other camera movements can correct such a distortion of space.

Vaughn

[Bryan Lemasters]

The roof over the pumps doesn't bother me so much (and it is slightly wider than the building, which exaggerates it somewhat), though I know what Vaughn is meaning - kinda the "big schnoz" look when doing a portrait with a wide lens. What I see is a slight overcorrection of the front rise. The upper facade of the building seems to widen as the eye move up. This seems to be pretty common. I noticed it in 2 or 3 pics in the churches and cathedrals thread a while back. I think the key in correcting converging lines, whether it is on the horizontal plane or the vertical, is to not completely correct it - and as the angle of view increases it becomes more important to hold back on correction.

I think this might all be "nitpicking" to some degree with Steve's photo, though. It looks pretty good overall, AFAIAC.

[Steve M Hostetter]

Hello,,, I think a big part of the problem with this example is that the structure at the top is a fake wall that rises above the main gable roof that is hiden ...
This fake wall to the right is leaning forward in an out of level postion ,,, no doubt a product of over one hundred years of being a wind foil in the heart of the flatlands of central western Indiana.. In order for me to get both shed and fake wall to match I'd need a come-along and a buck strong Amish fella,,, "nail it Franz"

[Mark Sampson]

It's unlikely that the subject itself is perfectly square, which makes camera movements even trickier. Myself I'd like to see a little more space at the right edge of the image; the building seems crushed up against the edge of the frame. Otherwise nicely seen.

[Bill_1856]

What the camera shows is the correct perspective.
For better or worse, what we've come to expect in the final print (or tranny) is actually a false perspective where all the vertical and horizontal clues appear to be parallel to the edges of the picture and perpendicular to each other. This can be achieved only in a single plane by the use of swings and tilts, but anything out of that plane (such the roof) will appear trapazodal, or ovoid instead of round.
How to make this visully acceptable is where the "art" of photography comes in.