Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: larkis on September 02, 2013, 01:13:51 pm
-
Has someone found a method to prevent photomerge in PS from killing the fidelity of images ? The attached image shows what happens at 1:1 after photomerge had it's way with the images.
-
Has someone found a method to prevent photomerge in PS from killing the fidelity of images ? The attached image shows what happens at 1:1 after photomerge had it's way with the images.
Hi,
Photoshop uses bicubic resampling for many of its distortion/keystone correction activities. This is a rather sub-optimal method, as you have experienced. The only remedy is to apply a significant amount of deconvolution sharpening (e.g. Smart sharpening, or a better method like FocusMagic or Topaz Labs Infocus).
Dedicated panorama stitching software usually offers a choice from several more advanced resampling algorithms which produce much higher detail and micro-contrast. Sometimes even too much detail and potentially ringing artifacts, therefore the choice from several methods. Methods that use Lanczos windowed Sinc resampling methods are often much better in keeping the microcontrast when small distortion amounts are involved.
You can try Hugin (http://hugin.sourceforge.net/), a free pano stitcher with lots of capabilities, to see if that does better than Photoshop. When you do a lot of stitching, PTGUI Pro (http://www.ptgui.com/) is an allround professional alternative with overall good performance for multiple computer OS platforms. AutoPano Pro/Giga (http://www.kolor.com/image-stitching-software-autopano-giga.html) is also useful for more automatic work on large amounts of pano shots, but when the stitching is difficult it's not always as fast as PTGUI at getting good results.
Cheers,
Bart
-
Hi Bart,
I have not tried PTGUI Pro but I have been a fan of (free) MS-ICE for a while. How do you think it compares?
Jack
-
I have not tried PTGUI Pro but I have been a fan of (free) MS-ICE for a while. How do you think it compares?
Hi Jack,
MS-ICE does the automatic stitching (and blending) quite well, but the resampling algorithm is apparently (according to a Microsoft spokesperson (http://social.microsoft.com/Forums/en-US/45f66b33-c1a0-4091-8c6b-4d8ddd43c48d/force-disable-of-image-scaling-and-rotation)) something similar to Photoshop's bicubic sharper... I do not see any user selections to change that, and do know that while it gives the result some punch (which may help smaller JPEG source images some), it also will create aliasing artifacts, especially when down-sampling.
PT-GUI, as do many of the other stitchers, offers a whole range of interpolation algorithms (see attachment) which allows to adjust to the subject matter at hand, and whether down-sampling is applied.
Cheers,
Bart
-
Before I use PS's Photomerge for my photos, I process each of them first with DxO (which performs automatic sharpening and other edits), so to my knowledge when I subsequently transfer them to Photomerge, there is no processing beyond the actual stitching of the photos. Anyway, with this method i have never noticed any degradation in the quality of the initial photos to how they subsequently appear in the Photomerge stitched output. but I could be wrong, and not have noticed any difference.
-
Got it, thanks Bart