|
|
|
|
|||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
||||
|
|
|
|
|
|
|
|
|
|
|
||||||||
|
|
||
|
|||
Digital Post Processing Example: Rescuing a Poor Photoin Tutorials |
||||||||||||||||||||||||||||||||||
By dv2529/Dave (3,575) 
on March 6, 2007 6:29:26 PM CST
Introduction IntroductionAlthough I am not a bird photographer, for someone in an urban area who usually has nothing more than sparrows and a few pigeons in the garden, the sudden arrival of a bird of prey - amongst a scattering of pigeon feathers - just called for the camera (I did momentarily have a moral dilemma - pigeon rescue or camera? - but hey, who am I to interfere with the course of nature? I suspect it was too late for poor Mr. Pigeon anyway, but yes I did feel a bit sad/guilty when I saw Mrs. Pigeon tottering about on her own a bit later on). Anyway, we've all been there many times - a photo opportunity presents itself but things just aren't right ... it was a winter day, in the UK, dark clouds and raining. And the birds landed in the furthest dark corner of my garden and I don't have some gigantic L series lens for my 300D (I do have a EF 75-300). But it was an opportunity not to be missed - so ISO 800 set, umbrella in hand and careful sneaking across the garden commenced. I knew the pictures were going to be very dark and noisy... but post processing can help dramatically (the important thing is that they are not blurred or shaken). Here I will walk you through in detail the steps I took to improve this dark noisy picture, showing amongst other things the core technique of blurring the background around the subject. I used PaintShop Pro 9 (PSP) however PhotoShop etc. will be very similar. 1. ORIGINAL PICTURE:
The original is too dark, poor crop, excessive DOF, badly angled in relation to the ground and log-roll behind the bird, and there are distractions like the numerous feathers and the contents of the pigeon's stomach pouring out; none of this could be helped really... the conditions were dire and the bird was ready to fly any second so there was little time to improve the shot. Critically, however, the image is not shaken, thanks to high ISO, a tripod and an infrared shutter release. 2. VISIBILITY2a. Gamma CorrectionI always adjust gamma as the first step in improving the brightness of an image. In PSP usually an adjustment of 1.3 - 1.4 is ample, however here I used 1.5 as it was really dark; you can see the improvement here:
2b. Brightness/ContrastIncreasing the Gamma can leave images looking a bit washed out so I virtually always follow on with some brightness & contrast. (here PSP settings were 10 and 14 respectively to increase both of these):
3. ROTATION AND CROP3a. RotationIt is best to avoid rotating an image if at all possible due to the resultant degradation in quality, however now that we can see the picture more clearly we can see the log roll is angled severely across the picture - so I rotated right by 5 degrees. This does not sufficiently adjust to correct the picture but it is a compromise - we do not want the bird leaning over to the right. Additionally I knew my final crop would be vertical orientation, so less of a correction is required here:
Top Tip: When rotating, use a background colour that does not blend in - this will ensure you do not accidentally include any of the new background when cropping later. 3b. Crop #1I don't want to work with the whole picture as it stands so I crop down to a rough area to make things easier. I will crop again later. Remember to set the selection tool feather to 0 when cropping.
4. NOISE AND DOF4a. The Problem Of NoiseBecause ISO 800 was used to keep the shutter fast and avoid shake, and because the light was dire, there is a lot of noise in the image. The image below shows a close-up - note how the background looks blotchy and speckled:
The bird itself has this same noise but it will be less apparent due to the texture of the feathers. Therefore, I opted to use a gaussian blur on the background scenery to reduce the noise. There are various tools that could have assisted here - median/averaging, noise removal etc. - however the other key bonus of using a blur is that it creates an artificial depth of field effect - adding a similar foreground blur to the ground in front of the bird will draw the viewer's attention much more to the subject matter. The key trick with blurring around the subject is to ensure that the subject's edges do not bleed out into the blur that is applied. Here, we will achieve this with extra layers and by deleting the bird from the layers we apply the blur to. 4b Create Duplicate LayersThe image at present belongs in the layer known as the Background. In this step, I created a new layer which was a duplicate of the background, i.e. it is a bit like putting an acetate version of our picture over a printed paper version; we can then manipulate the acetate version and cut holes in it to show the original background picture below.In the Layers palette, I right clicked the background and choose Duplicate. This creates a new version of the image in a layer called "Copy of Background".
I then renamed the layer as "Blurred Upper"; this will be used to blur the scenery behind the bird. I then repeated the process to create a third layer, "Blurred Lower" which will be used to blur the nearest foreground in the picture. It is important to remember that modifications and copy/paste type operations only affect the layer currently highlighted in the layers palette. 4c. Blurred Upper: Remove The BirdAs we are going to blur the scenery behind the bird, it is necessary to remove the bird from the layer in which we do this, otherwise the bird will also be blurred and it will bleed out into the rest of the picture slightly, creating a soft focus effect. (An alternative strategy would be to deform the bird within the new layer such that it was smaller e.g. smudge it inward, deform it etc.) We will only blur 3/4 down the picture as true DOF would result in the ground around the bird being in focus.To remove the bird, I selected the "blurred upper" layer in the layer palette and used the freehand selection tool, in point-to-point mode, with a very slight feather of 3 pixels so no edges are too harsh, and selected the bird outline:
I then pressed Delete - at this point nothing appears to have happened, however we have 3 visible layers all with the same picture and all on top of each other - cutting a hole in one will just show what is below which in this case is the same. Each layer can have its visibility toggled on and off - doing this for the other two shows the change we've made:
I then saved the selection of the bird to disk - using the Selections menu, Save to Disk option. This will allow us to reselect the shape of the bird again, exactly as we have it now. 4d. Prepare to Blur the ImageKeeping the "blurred upper" layer selected, now with missing bird, I set the selection tool to a rectangle and the feather to 138 (i.e. a big feather) and then selected the top 3/4 of the image (the big feather will help blend the blurred scenery to the non-blurred area of the ground, thus creating a DOF like effect):
4e. Gaussian Blur - UpperAfter applying a strong-ish Gaussian blur (setting in PSP was 10) the deleted outline of the bird is no longer crisp: (also notice the blurring fades nicely away at ground level due to the feather we applied):
If this layer was placed over the visible background layer then the blurred edges on the bird's outline would interfere with the sharp bird of the lower layer. We must delete these soft edges. 4f. Reload SelectionI reloaded the previously saved selection of the bird - it can be seen how far the blurring has overlapped this selection:
4g. Delete the Overlapping BlurringPressing Delete will once again leave a nice clean space where the bird was previously - the Background layer below will fill this gap once set visible again:
4f. Check the Blurring Against The Background LayerToggling the visibility of the Background will now fill the space in and show us our image so far:
Compare this image with that in 4b - the scenery is certainly more blurred but the bird looks a bit cut out and stuck on. We'll correct that soon. 4g. Gaussian Blur - LowerNext I blurred the ground closest to the camera - the technique is more or less identical to the upper area but rather than just deleting the bird, we have to delete everything but the area we are blurring. This is because this layer is top of the pile of layers and so would otherwise obscure everything below. So I chose the rectangle selection tool, a reasonably large feather (88 pixels) and then selected the top 80% of the image ... then pressed Delete.
The effect of the feather can be seen clearly in the above image - the remaining section fades toward the top where the deletion tailed off in strength. Notice in the layer palette I have ensured the "blurred lower" layer is selected and toggled off the other layers. I then selected the whole of the frame and applied a Gaussian blur. Unhiding the other layers the composite image now looks like this (notice the DOF effect we have achieved):
4h. Layer Opacity AdjustmentAs it stands, the 3 layers have equal weighting in the picture... it helps to reduce the strength of the newer layers relative to the Background in order to improve realism. To do this I decrease the strength of each using the sliders in the layer palette until a better effect is visible:
5. MERGE, CROP & REMOVE DISTRACTIONS5a. Merge layersOnce I was happy with the layers' appearance, I right clicked on one and chose to merge them all into the Background.5b. Crop #2Next I cropped to the final image shape - don't forget to set the selection feather back to zero before doing this.
5c. Remove DistractionsNext I would look at the cropped image and remove or alter anything that might distract overly. (strictly speaking it would have been better to do this before the layer duplications, blurring etc. but I forgot).
Here I have highlighted several items - some feathers at the top that are a little bright, the grass blade and the content of the pigeon spilling out. I use a mixture of the clone brush - usually with a medium to low opacity - and basic copying and pasting random shapes from similar surrounding with significant proportion of feather on the selection. For example, I copied a number of "chunks" of feather to improve the pigeon's spillage... if they looked too similar I might reverse the chunk to make it less obvious, or stack one over the other. It is good practice to use additional layers to do the adjustments and then to merge them together once happy. See the final image for the corrected items above. 6. SOFTEN, SHARPEN AND OTHER STUFFTo give the bird just a little more blending into the picture and obvious hard edges can be softened using the softening brush. Areas that need to stand out can benefit from sharpening e.g. eyes and the beak, however the risk with sharpening is that the image noise will be accentuated. The other thing well worth doing is to view the image on a number of screens - an LCD may show noise or issues that cannot be seen on a CRT.The following show key areas of adjustment - here I used softener (red), sharpening (blue) and median (green), the latter specifically to treat some noisy areas with obvious magenta specs.
Additionally, I used some of PSP's noise removal tools very lightly on areas where there was obvious noise still visible. This was subtly done - create a new duplicate layer, set a large feather and then select areas requiring treatment before using the tool. Then set the layer to about 30% visibility and merge back together. Top tip: the eyes in any picture, no matter if bird or person, are vitally important. A viewer will not notice if the 6th stripe down on the left side of the bird's breast has an imperfection, but anything wrong with the eyes will stand out dramatically and can ruin an image. Spend time to get the eyes right! Another top tip: If resizing the image, always do sharpening afterwards. Ideally become familiar with the Unsharp Mask (USM) tool, as it allows more control over the process, but otherwise the general sharpen option and sharpen brush should suffice. 7. ADD BORDERS AND TEXT FOR FINAL IMAGEA border around a picture can make a huge difference - ask yourself how many pictures hang in an art gallery without a picture frame? This is more so when the picture could do with a boost. Here I chose a black frame - the image is quite dark and so the black frame emphasizes that the content is lighter than black.To apply the frame I simply used PSP's Add Border tool - 60 pixels top, left and right, and 160 at the bottom to allow space for text. If you cannot decide what colour a border should be or what sort of text to add, have a look at other pictures on this site; there are plenty of good (and bad) examples to copy. Text should be added with the anti-aliasing options enabled, this will result in smooth edges to the letters. And here is the final picture - undoubtedly not the same quality as if the sun was shining and the bird was tethered - there is still a lot of noise - but compared to the original picture it is certainly a dramatic improvement.
I hope that has been useful. Dave
Read 14,086 times
|
