Filter>Digital Camera>Rectify

[Lundberg02]

I'm having some difficulty understanding this filter. It opens with a 36.7% crop selection in the middle of the image which can't be moved. Also, the checkbox Crop is checked. I can move the corners of the selection and get a a skewed image, but since the selection can't be moved or enlarged, I can't do much with it. Perhaps I'm missing something. The two dimensional sliders in Photoshop are much easier to use to correct perspective. I don't really understand why you would want to do a crop in this filter.
The whole thing has the feel of being backwards.
I really like the Lens Correction Filter, though. I just can't get my mind around this Rectify.

[photoken]

It's a perspective correction tool. Place the four corners of the rectification rectangle on four corners of what is in reality a rectangular object in your image and hit "OK". If you de-selected the "Crop" option, you'll see that the image has been rectified and there are white borders at the edges where the image has been distorted to correct the perspective. If you select "Crop", the image area will be automatically cropped to the maximum size that still eliminates those white edges.

[greenmorpher]

I'm not a fan of that rectify tool and the lens correction is pretty basic too in my view (but then, I think it has to be).

I use PTLens as a plug-in, and as we've been discussing in another thread, you can also use it as an External Program (runs faultlessly on both Windows and Mac).

The perspective correction has sliders, rotation, and a grid for guidance, and you can enter numbers for precision. There is CA correction too, and PTLens's lens correction is keyed to particular cameras and lens combinations and is very sophisticated. $25 for a lifetime use at ePaperpress and about a 5.3MB download for the Mac version (probably smaller for Windows).

I can see the logic behind PL's rectify tool, and at first blush, it is good, but in practice it doesn’t work so well. The lines are too thick and the adjustment movements too small. Moving unrestrained corners which can effect both the vertical and horizontal dimensions is not a great way to go. There ought to be some constraints.

At the most basic level, I have asked several times for PL's rectify tool to default to all square; I can see no reason at all for it to retain the last setting which inevitably is dealing with a different picture.

But I'm not concerned, really, I just don’t use it. I might if it worked a LOT better.

As for the lens correction -- it is simplistic. Lots of modern zooms produce moustache shaped distortions. You can’t do much with them with a tool like PL's lens correction. That's not putting the PL tool down, I very much doubt whether a usable tool would be possible to handle the complex distortions.

Cheers, geoff

[Herbert123]

+1 PTLens

[Lundberg02]

Thank you , photo ken, for that explanation. That still leaves me wondering why there's no preview and why the filter retains the last skew when you open another image. Why can't the selection be moved? Not user friendly at all. I have looked at PTLens, but the process of obtaining a usable camera profile is a bit daunting and I wasn't able to determine a priori whether my camera is in their library. My camera, a Fujfilm, seems to produce fairly simple barreling and perspective which Photoshop removes easily.

[photoken]

Lundberg02,
The selection can't be moved as an entire selection because that's not going to help with correcting perspective distortion. You "move the selection" by moving the corner points individually.

I suppose there's no preview because the rectification just simply works....

The last skew is retained because...ummm...errr...it's a feature!

[bkh]

Thank you , photo ken, for that explanation. That still leaves me wondering why there's no preview and why the filter retains the last skew when you open another image. Why can't the selection be moved? Not user friendly at all.

Maybe you should try PL's crop tool – make a selection and press Strg/Cmd and drag the green handles to (un)skew the image. It's my preferred way of straightening and unskewing images because you sometimes don't want to completely unskew the image because this often looks unnatural.

Cheers

Burkhard.

[photoken]

Lundberg02,
Now that I've had a chance to think about it a while, I realize that your questions about the preview and retaining the skew are kind of linked together:
When the rectified image is displayed in the main editing area, that's the equivalent of a "Preview". If it needs adjusting, the Rectify window opens with the retained skew so it's easy to tweak a corner or two. It's a system that suits the way I work, but your mileage may vary....

[Lundberg02]

I'm going to take a more thorough look at PTLens. Also appreciate the tip on the PL Crop Tool which is pretty obviously the father of Rectify. I doubt I will ever be comfortable with Rectify. Photoshop's Lens Correction is almost trivially easy to correct my wide angle distortion in art photographs.
I am a fan of Photoline nevertheless. The first time I used it it impressed me and I like the opening with last image time saver.
bkh: What on earth id Strg/Cmd? Is this something in Windows?

[bkh]

I'm going to take a more thorough look at PTLens. Also appreciate the tip on the PL Crop Tool which is pretty obviously the father of Rectify.

Rather the converse – rectifying with the Crop tool was only introduced with PL 17, as far as I remember.

Photoshop's Lens Correction is almost trivially easy to correct my wide angle distortion in art photographs.

Do you mean distortion (bending of straight lines) or perspective correction (make lines more parallel), or a combination of both? Distortion is easier to correct with tools like PTLens because the correction is automatic via a lens database. Alternatively, there's PL's Lens correction filter for that.

bkh: What on earth id Strg/Cmd? Is this something in Windows?

Sorry, it's the Ctrl key on an English keyboard (Strg in German/Win), Cmd on Mac.

[greenmorpher]

Thank you , photo ken, for that explanation. That still leaves me wondering why there's no preview and why the filter retains the last skew when you open another image. Why can't the selection be moved? Not user friendly at all.

Maybe you should try PL's crop tool – make a selection and press Strg/Cmd and drag the green handles to (un)skew the image. It's my preferred way of straightening and unskewing images because you sometimes don't want to completely unskew the image because this often looks unnatural.

I DIDN’T KNOW you could do that! That works much better than the Rectify tool because you retain the oblong outline of the crop tool with its narrow, clear lines so it is much easier to see what you are doing!

How bizarre!

Cheers, geoff

[greenmorpher]

Thank you , photo ken, for that explanation. That still leaves me wondering why there's no preview and why the filter retains the last skew when you open another image. Why can't the selection be moved? Not user friendly at all. I have looked at PTLens, but the process of obtaining a usable camera profile is a bit daunting and I wasn't able to determine a priori whether my camera is in their library. My camera, a Fujfilm, seems to produce fairly simple barreling and perspective which Photoshop removes easily.

If you camera is in the PTLens library it will show up.

You download and instal PTLens on a trial basis. It gives you the opportunity to use it o 10 images. Open an OOC pic in PTLens, and if you camera is in the database, it will show as the camera used in the panel under the picture. PTLens will get the info from the EXIF data in the pic. If the camera is fixed lens, then that will show too, and it will show the focal length used at the time of taking the picture (also from the EXIF data) and make the correction to it when you click "Apply". If you camera is an interchangeable lens model, you will have to identify the lens from the drop down menu, PTLens ghen identifies the focal length used and you press "Apply" to apply the correction.

If you camera is NOT in the database and you want the ad vantage of automatic correction for evermore, you go to the trouble of shooting a modern building or whatever as per the instructions. Send in the images, and Tom will do the maths to provide the correction(s).

If you don’t want to do that, well, PTLens is not for you for lens correction! BUT it is still a very handy tool for rectifying perspective and fixing CA.

Cheers, geoff

[Lundberg02]

I guess I have to give both PL methods a try now. I will present my findings to the grand jury in a few days and indict a ham sandwich.

[Lundberg02]

Photoshop recognizes my camera as a Fujifilm but not the model. I would guess the same for PTLens. I might just do the shots Tom wants though.