Sunnely Loc: Wisconsin

I can see the building is slanted. What did I do wrong? I was trying to focus on another subject across the street. Then, I heard the siren and quickly switched to the EMS and pressed the shutter.

(Download)

LJLRenner

Just straighten up the entire picture. Easy!

Linda From Maine Loc: Yakima, Washington

A combination of wide angle and your perspective.

tommystrat Loc: Bigfork, Montana

I think parallax is the culprit. Square buildings in the background and a square subject in the foreground will almost always look like one or the other is slanted. Especially when the buildings are taken essentially straight on and the foreground object is shot at an angle. Much like train tracks that are actually parallel but appear to merge in the distance. You can tweak this in post-processing using the Crop (or maybe Transform) tools in Photoshop if you use that program. Image is nice and sharp, though! ;-)

tommystrat Loc: Bigfork, Montana

Linda From Maine Loc: Yakima, Washington

Resources:

http://www.boltnev.com/panoramastitcher/parallax/

https://www.brighthub.com/multimedia/photography/articles/66490.aspx

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Stardust Loc: Central Illinois

Think Linda from Maine and Tommystrat nailed it... in under 12 minutes. Don't you love UHH.

JohnSwanda Loc: San Francisco

I think I would rather see the tilted buildings than crop into the ambulance, which is the main subject. You also have more of a sense of motion of the ambulance in the original.

Bill_de Loc: US

Compromise.

E.L.. Shapiro Loc: Ottawa, Ontario Canada

It needs some excitement! Like a speeding ambulance!

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

That is not parallax. Parallax is a phenomenon that occurs when you view something from two different positions, like with binocular vision (human eyes) - the left eye does not see exactly the same thing the right eye does. In photography, when you rotate a camera to do a panorama, if you have something in the foreground that obscures the background, a parallax error can occur. This is when, as you rotate the camera, you change it's point of view and what is obscured when the camera is in one position is not the same as what is obscured when you rotate the camera to the next position. Finding the "no parallax point" on the lens and using that as a pivot point for the lens will minimize parallax error.

With film cameras, particularly rangefinders and twin lens reflex models, the viewfinder was separate from the optic used to take the picture, which often resulted in a different point of view when the camera was used for closeup and macro work.

https://en.wikipedia.org/wiki/Parallax

What this is pure and simple is a wide lens used with the camera's sensor tilted up, and also the camera not held level. The converging verticals (or horizontals in other cases) is known as keystoning, and can be addressed by keeping the camera level to avoid converging verticals, and parallel to a wall or side of a structure to avoid converting horizontals. Wider angle lenses do have a characteristic "extension distortion" which can exaggerate the appearance of keystoning.

https://en.wikipedia.org/wiki/Keystone_effect

kschwegl Loc: Orangeburg, NY

The EXIF data says you used a D7200. There's an menu option to show a framing grid in the viewfinder. It will help you keep the camera level, which is all theat's wrong with the photo. Check the manual, but I believe it's a "display option".
P.S. I have a D7200 and I love it.

Ken S

kschwegl Loc: Orangeburg, NY

Back again, Got the camera out. The option is in the custom settings menu, shooting display, option D7. It's called Viewfinder Grid Display.

Ken S

dbfalconer Loc: Salida CO

I agree! Lots more energy in the original.

E.L.. Shapiro Loc: Ottawa, Ontario Canada

So...your original question was about "what" did you do wrong(?). Nothing really! You quickly reacted to a situation and you wanted to tell a story. You grabbed the shot! So now you have a picture of an EMS unit. The sound of a siren is alarming and exciting as is the sight of a "lit up" speeding ambulance! I don't see that excitement in that image- so I messed around with it! Those shots of aircraft with "frozen" propellers give me the willies- when the props or rotors stop, especially on helicopters, they fall out of the sky- so I like to blur them!

My point is, if you want a technically perfect image of an ambulance with a building in the background all you need to do is go to your local hospital's ER department- you will likely find one parked nearby. You can use a normal lens, or a tilt shift wide angle one if you have that, keep the camera parallel to all the vertical lines and negate the forced perspectives and distortion that results from wide angle usage and incorrect camera positions.

Gene's explanation of the optical phenomena is 100% correct- study those details. When you grab a shot and everything seems wrong oftentimes it good to use all the distortion, tilted and skewed lines and whatever else is "bad" to convey a mood. Next time you hear the siren perhaps slow up the shutter a bit to capture the lights and the movement. Or, here's an idea- create a self assignment about first responders. Talk to the EMS guys and gals, the local constabulary and the fire department in your community. They may "light up" a vehicle for you when it is off duty or out of service- if you ask nicely and promis display the images at you local city hall or at another public place.

Of course you want to master your camera and all the techniques but don't forget the fun and creativity. But...if you are aspiring to a career in commercial photography and/or need to show a picture-perfect shot of an ambulance- like for the folks who manufacture or sell ambulances- that's an ambulance of a different color!