how to straighten building - photoshop

[megan_stone]

<p>i have done a portrait of someone with their home in the background using my 50mm lens.<br>

it seems that the sides of the frame... the home's walls are not vertical/straight.<br>

i have tried selecting the entire image, transform then Skew. but it seems to also affect the center of the image/portrait... how can i straighten the lines without affecting my subject?</p>

<p>many thanks</p>

[Stock-Photos]

<p>It seems that "keystoning" is the problem you're trying to correct. Ctrl+shift+R for lens correction. Then select the custom tab. Play with the perspective sliders.</p>

[Mattman944]

<p>Edit->Transform->Perspective is normally how I do this. Any rotation in the image should be removed first. It will affect your subject some, but if you adjust it so you make them thinner, they probably won't notice.</p>

<p>Post an example and you will get better advice.</p>

[john_a5]

<p>The problem with the lens correction feature is that you can't reposition your image within the frame as you correct it. Sometimes that isn't an issue and sometimes it is a big issue as it crops in places that are important.</p>

<p>Using the Transform feature will give a more controlled result as you can move the image around in the frame to conserve important areas. But correction at one end or the other will either create a more squatted/compressed view or an elongated view. The secret, and what is less an issue with the stress on the resampled pixels, is to work at both ends, pulling one end in and the other out. If you do this equally, you keep the proportions of the scene in tact and end up with less issues at your corners where pixels were resampled to accommodate your changes.</p>

<p>The big advantage of the Transform option is that you can move the image around in the frame to preserve the important parts of the image if they move out of frame as you correct the perspective distortion. You can also increase the size of your canvas before you do the transformation in order to allow the image to grow in the frame as you correct it--cropping as desired when you have everything corrected.</p>

[digitaldog]

<p><strong>IF</strong> you have the raw, and you are using an Adobe raw converter, by all means start by applying Lens Correction (manual or auto if you have a profile for the lens). You can straighten there as well (non destructively) in by typing the R key and using the Angle tool. </p>

[howard_m]

<p>Shouldn't ACR also be able to do that correction using a JPG? I haven't tried it recently but it would seem simple enough</p>

[digitaldog]

 

 

<blockquote>

<p>Shouldn't ACR also be able to do that correction using a JPG? I haven't tried it recently but it would seem simple enough</p>

</blockquote>

 

 

<p><a name="pagebottom"></a><br>

It can but you lose all the benefits of raw processing and at this point, might as well be using Photoshop.</p>

[JDMvW]

<p>You can get around the 'cropping' problem mentioned under lens correction by using the 'scale' slider to reduce the overall size so there is no cropping.</p>

<p>In the newest versions of PS this can be done to jpgs under Filter>Lens Correction. In older versions, you can open a jpg image in ACR from Bridge by right clicking on the image and choosing "Open in Camera Raw"</p>

[jens_g.r._benthien]

<p><strong><a href="http://epaperpress.com/ptlens/">PTLens</a></strong> is your solution. Runs standalone, includes a RAW converter or can be used as a plug-in for professional image editors like <strong><a href="http://www.pl32.com">PhotoLine</a></strong> or the Adobe Products.</p>

[JeffOwen]

<p>In later versions of Photoshop under transform there is the Warp feature. If you are careful you can adjust part of the image to straighten etc. Mostly I use the Distort feature in transform as this has better control than skew or perspective.</p>

[robert_k1]

<p>There are many ways to skin this cat.</p>

<p>John's comments about avoiding cropping and preserving the original's aspect ratio are right on, for those who care. Here's a thread on the same subject with an example:</p>

<p>http://www.photo.net/digital-darkroom-forum/00WeiM?start=0</p>

<p>Here's another quick and easy method. Not perfect, but suitable for many situations.</p>

<p>http://help.adobe.com/en_US/Photoshop/11.0/WSfd1234e1c4b69f30ea53e41001031ab64-7630a.html</p>

<p>Very often, after correcting the perspective, there are still barrel distortions. That's when I would use the Warp transform tool, which calls for more careful manipulation.</p>

 

[scott_ferris]

<p>Robert,</p>

<p>I was just looking for that screen shot of mine! </p>

[emil_ems5]

<p>I read J.K.'s "Link" that describes how to use the cropping tool in Photoshop to rectify keystoning. I was very impressed by this description and the possibilities it seemed to open up for me. However, when trying the approach in question in my Photoshop CS5 Extended, the rectangle "Perspective" which you are supposed to check, didn't light up, that is it was not working; so I could not follow the instructions provided in the link. Has this useful feature been de-activated in CS5?</p>

[scott_ferris]

<p>Emil,</p>

<p>It is still there, but the "perspective" box does not light until after you have drawn your rectangle. Also I highly recommend using the grid pattern to help, this is found in View-Show-Grid or keyboard shortcut Command + ' on a Mac, click the same again to make it toggle away.</p><div></div>

[emil_ems5]

<p>Thanks Scott, but it did not become active even then. But I have discovered since then what was the problem. I use to work with ACR files saved into Photoshop as Smart Objects. Those cannot be dealt with in the manner described, they must be rasterized first.<br>

I have now tried the crop tool for correcting perspectives and have to say that, although it is easy and quick, it has some serious drawbacks as compared to using the Command EDIT/TRANSFORM/PERSPECTIVES. </p>

<p>(1) It is usually not pleasing to the eye, neither does it the picture any good, to correct the keystoning by a fully 100%. All experienced photographers know this and stop the correction a smite earlier. This cannot be done using the crop tool, at least not with any precision. In contrast, its is easy to do with EDIT/TRANSFORM/PERSPECTIVES.</p>

<p>(2) Similarly, to get a pleasing and realistic result, the correction should work as it does with large format cameras (using the shift-lens facility). This means that proportions should be maintained throughout the correction process. This cannot be done by using the crop tool (and neither can it be done by using the LENS CORRECTION/VERTICAL CORRECTION tool in ACR. Again, this is possible to do with EDIT/TRANSFORM/PERSPECTIVES. The way of doing this is to, symmetrically, draw the picture apart on top and push it in on the bottom (respectively dragging and pushing the upper and lower corners of the correction rectangle).</p>

[JDMvW]

<p>One thing about Photoshop that I love is that there is usually more than one way to do any particular task.</p>

<p>However, I am a little puzzled by the</p>

<blockquote>

<p>neither can it be done by using the LENS CORRECTION/VERTICAL CORRECTION tool in ACR</p>

</blockquote>

<p>which is also now available, in essentially the same form, from Filter>Lens Correction in PS CS5.5, itself.<br /> I have no trouble at all in using this path to make "pleasing and realistic" results. I still want my TSE-E 17mm lens, mind you, but between my PC-Nikkor 35mm lens and Photoshop, things work pretty well. You just need to use judgment and <strong>all the sliders</strong>, if needed.</p>

[JDMvW]

<p>Here's the combined filter> "lens correction">"custom" controls. Sort of one-stop fixing.</p><div></div>

[emil_ems5]

<p>JDM,<br>

Just to make myself clear: I also use the lens correction filter regularly (from ACR) to do the correction specific for my Nikon camera lense. However, I hesitate using the vertical correction filter to correct keystoning. Without having tested this in detail i still have concluded that this correction does not preserve the proportions of the object to be corrected. I do not seem to get the same results as by applying, symmetrically, the EDIT/TRANSFORM/PERSPECTIVES in Photoshop. Having said this, I have not carried out any exact comparison between the two approaches, so I would not mind standing corrected if you can show me proof to the contrary. </p>

[JDMvW]

<p>To me the PS tools seem to pretty well mimic what swings and shifts do for <em>perspective</em> on a 4x5 camera (which I used to use regularly). Even on large format film, you do sometimes pay in price in using the outer reaches of lens coverage even on a view camera. Of course, you can only change the <em>plane of focus</em> on the camera - not in Photoshop.</p>

<p>I do prefer to get it right in the camera with a shift lens (or, when my ship comes in, a tilt and shift lens). But I have taken lots of pictures when I haven't had such a lens available, and the post-processing solution is often better than falling over structures.</p>

<p>You do need to watch and change horizontal perspective too, of course, in many cases. Vertical adjustments may not be the only thing you need (you keep saying you don't like vertical, so I am wondering if you are looking at the rest of the tool palette)</p>

<p>I confess, I've never much liked what the built-in lens-specific 'fixes' are in terms of corrections, and over all I pretty much either leave the image alone or correct it manually. By the time you've gone through the whole tool palette in ACR and in the new lens correction procedures, there is a very large range of different ways to solve aberrations, distortions, and other problems.</p><div></div>

[tom_mann1]

<p>One has to be careful not to attempt to correct large perspective distortions in your starting image because you can wind up with some very non-realistic looking objects. This is especially important with horizontal perspective distortions.</p>

<p>For example, the image attached to this post was only corrected for a small amount of vertical perspective distortion and gives you a fairly normal view of this house.</p>

<p>In contrast, the image attached to the next post shows what happens if you also try to completely "correct" the horizontal perspective distortion. Note that the (viewer's) RHS of the house has become much too massive, whereas the LHS of the house looks oddly small in both height and width. Also, note visual inconsistencies such as the fact that you can still see the (viewer's) LHS of the roof of the dormer sticking out perpendicular to the main axis of the house, whereas the non sloping main roof line suggests that you are standing directly in front of the house and looking perpendicular to the front wall, so you shouldn't be able to see that part of the roof.</p>

<p>Just my $0.02,</p>

<p>Tom M</p><div></div>

[tom_mann1]

<p>And here is an attempt to completely correct for the horizontal perspective distortion that illustrates the problems that can result from this.</p><div></div>