How do you know when it's straight?

[SandeeWig]

Often times when I'm processing a photo, it needs a little straightening. No big deal, right?

Wrong!

My question pertains specifically to straightening images shot at an angle (or has angled lines). I'm using the following picture as an example. I used the lamp post in the foreground as my line, but the more I stare at this, the more crooked it looks. Does it look a little off to you too?
Another example from this set is here.



So often I find myself battling over which lines in the photo to use as my guide to determine when it's straight. Just when I think it's straight, something else is obviously leaning.

My question is, then, how do you know which line in the picture to use as the guide? I know it depends on the perspective, but is there some "rule of thumb" I can keep in mind when straightening the lines?

Any help or suggestions would be much appreciated.

[sandman935]

Your problem is lens distortion. If you're using PhotoShop, you can correct it using the lens correction filter.

Here's an example of before/after:

Rand Barber Shop

[peeperita]

i try to go with the most prominent vertical.....in your image, i'd call that the right side of the wall with the door on it....

peeper

[SandeeWig]

Originally Posted by sandman935

Your problem is lens distortion. If you're using PhotoShop, you can correct it using the lens correction filter.

Here's an example of before/after:

Rand Barber Shop

Wow! Thank you so much! You were right on the money!! I had not even considered this and when I ran it through the lens correction, I was surprised at how distorted it really was, as evident by how much of the picture I lost after correcting it.


I purposefully left the space in the bottom corners to show how much was lost. If I were to crop it properly I would have to totally lose the flag pole, and possible the top of the steeple if I kept the same dimensions as the original.

I will have to keep this in mind for future reference when taking shots of these kinds of subjects. Do you find that nearly everything needs a lens correction? How much space do you allow for it when composing your shots?

How annoying!

[FGPhotography]

Originally Posted by sandman935

Your problem is lens distortion. If you're using PhotoShop, you can correct it using the lens correction filter.

Here's an example of before/after:

Rand Barber Shop

Where do you get this filter? I can't find it, although I do use PSE6 on Mac... perhaps that makes a difference...?

[dlroberts]

I would have used one of the long white lines on the face of the building rather than the shorter lightpost to make it straight -- but along the sides might be lens distortion if you were at the wide end of the lens. I'm not sure which problem you're specifying -- neither one is much of a problem to my eyes. I use PTLens when I shoot wide angle.

[wulf]

Pick a line - it depends on your vision for the picture. As you move to wider angles, the more the lines get distorted and you have to move your thinking from ruler-straight lines to what you are setting up as the focal point of the image.

If it really bugs you, try a longer focal length but stand further back to compensate (a good exercise if you want to understand the range on a particular zoom lens).

Wulf

[kencaleno]

The answer is to never go wider than 24mm, when making the image,then you won't get distortion. Regards,Ken

[wulf]

Doesn't the degree of distortion depend on how close you are to the subject as well as the focal length? I think the effect can look fantastic but it is better as a deliberate choice than something you are stuck with after the fact - get to know your lenses and the different effects they can produce.

Wulf

[SandeeWig]

Fawn, I don't know about PSE, but in PS CS2 it's under Filters > Distort > Lens Correction

dlroberts, thanks so much for your comments and feedback. I agree, I probably should've used (or at least considered) the white line in the front of the building, but my issues were more about the sides of the image. The flagpole and edge of the building on the right, for example, were leaning left. So, if I straightened that, the rest of the image appeared to lean right. It was windy that day, but not windy enough to make the entire side of the building lean!

wulf, thanks so much for the tip. I could definitely stand to do some tests with my lens and become a little more familiar with it so I know what I'll end up with before I get the photo out the camera. I agree, it could result in a cool effect...almost fisheye-like...if that's what I was going for. I have another image of this building that produced that very effect and is a better crop for that result (I think). If interested, I'll post it tomorrow as an example. I appreciate you taking the time to comment and your suggestions.

ken, thank you for your insight as well. This image was taken at 21mm, on my 18-55 lens, so definitely close to the widest angle it allows. The 24mm cut off is good to know, and it at least gives me something against which to compare my test shots.

Thanks again to all.