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Digital Darkroom

Post-Processing

Generally images taken on a Digital SLR Camera will need to have some post-processing done to them. The amount of post-processing really depends on the quality of lens that you use, quality of the image that you have taken, personal preference, and what you intend to use the image for.

You can adjust the 'processing parameters' in a DSLR camera so that the camera automatically adds contrast, sharpness, saturation, and colour tone to the photograph as it is captured but it is generally accepted that it is much better to set the camera's 'processing parameters' to standard and enhance the photograph using image editing software such as 'Photoshop Elements' or 'Paint Shop Pro' to do the post-processing.

Using RAW mode on a DSLR will allow you much more latitude in post-processing with the ability to alter the exposure, white-balance, colour, and sharpness etc. but file-sizes using RAW mode are much larger, meaning less photos can be stored on your memory card, than using Large/Fine JPEG mode. For this article i am going to assume that you have taken a photograph which has good exposure, is sharp, and is taken using Large/Fine JPEG mode (highest quality JPEG mode - not RAW mode).

Firstly it is a good idea to make sure that your monitor is correctly calibrated. A Google search will find many websites that help with software monitor calibration or a hardware calibration device such as the 'Spyder' can take the guess work out of calibrating your monitor.

Make sure your original images are backed-up and only work on copies of the original image.

Digital Photograph Workflow

A basic workflow might be something like this:
CROP
RE-SIZE
ALTER BRIGHTNESS/CONTRAST
SHARPEN
SAVE

A more advance workflow might look like this:
STRAIGHTEN IMAGE
CROP
RE-SIZE
REMOVE DUST SPOTS
LEVELS
CURVES (if required)
HUE & SATURATION
SHARPEN
SAVE


The basic workflow is rather simple but can be done very quickly. Below i will show you step-by-step how to do the more advanced workflow:

STRAIGHTEN IMAGE:
Straightening an image is usually only necessary when you take photos of aircraft on the ground or as they take-off & land. You see many photographs of aircraft landing, where the aircraft is horizontal but the runway and background are sloping, causing a very unnatural look to the image. It is very easy to put this right using image editing software. The 'Free Rotate' tool can be found in the 'IMAGE' menu and can be used to rotate the image a few degrees left or right. The hard part is knowing what is level and the best way to do this is to look for vertical lines in the image such as houses, posts etc and rotate the image until these are upright.

Sloping runway and horizon.

CROP:
The Crop tool allows you to select just the part of the image that you want to keep and disposes of the rest. Cropping is down to personal preference and you might want to crop the image to show the whole aircraft or crop just part of the aircraft for more of an arty photograph which shows more detail of the aircraft.

Using the Crop tool.

RE-SIZE:
The RE-SIZE tool can be found in the IMAGE menu for both Paint Shop Pro and Photoshop Elements. This tool allows you to re-size the image in pixels or alter the 'Document Size' in inches/cm. If the image is intended to be viewed on a monitor then you resize the photo in pixels or if the image is intended to be printed out then you can resize the photo in inches/cm. Make sure that the 'Lock Aspect Ratio' box is ticked so that altering the 'Width' size proportionally alters the 'Height' size, otherwise you will get a squashed image.

REMOVE DUST SPOTS:
Dust spots can sometimes show up on your photo especially when taking photos of aircraft against a blue sky with a Digital SLR Camera. They are caused by dust collecting on the camera's sensor and if you have a lot of dust spots then you will need to clean your camera's sensor. Modern DSLR Cameras now usually have built-in auto sensor cleaning which helps keep the sensor clean so this is less of a problem then it used to be.

Removing dust spots from an image usually requires the use of the 'Clone' tool This tool allows you to sample an area of the image near to the dust spot (right mouse button) and then clone that area (left mouse button) to cover the Dust-spot. The clone brush can be resized so it it covers the dust spot.

It is quite difficult to see dust spots on an image so the best way to view them is to 'Equalize' the image which will highlight the spots. 'Equalize' can be found in Photoshop Elements in the 'IMAGE' menu. In Paint Shop Pro go to the 'ADJUST' menu and select 'Brightness & Contrast' and then 'Equalize'.



Post-Processing workflow
Digital Dark Room.

LEVELS:
If you are using Paint Shop Pro then select LEVELS (ADJUST menu, in 'Brightness and Contrast') or if you are using Photoshop Elements then select LEVELS (ENHANCE menu). LEVELS shows three pointers/sliders underneath a histogram. The actual histogram represents the tonal range (contrast & colour balance) of the image with the left showing darkness, the right side showing lightness, and the middle showing mid-tones. LEVELS is a quick and easy way of quickly manipulating the image using sliders to get the desired exposure.

Levels and Curves tools.

CURVES:
The CURVES tool can be found in Paint Shop Pro in the same menu as LEVELS but you may not have it if you have Photoshop Elements. CURVES will allow you to adjust the image tonal range like LEVELS but will allow you much more subtle control to fine-tune the image. However, it is easy to over-use this tool and end up with an unnatural looking image, so be careful. You start with a box containing 16 squares with a straight diagonal line running from the bottom left to the top right. By clicking on the line you create points which can be moved to create a curve which alters the contrast etc of certain parts of the image. Experiment with this tool until you are happy with the result.

HUE & SATURATION:
The HUE & SATURATION tool can be found in Paint Shop Pro (ADJUST menu) and Photoshop Elements (ENHANCE menu). HUE & SATURATION will allow you to enhance the image with a bit more colour, if it needs it. Increasing the Saturation slightly should add alittle more colour in the image. Experiment until you are happy with the result but do not over-use or you will spoil the image.

Saturation & Unsharp tools.

SHARPEN:
The SHARPEN tool can be found in Paint Shop Pro (ADJUST menu) and Photoshop Elements (FILTER menu). The SHARPEN tool that we are going to use is Unsharp Mask (USM) as this offers much more control then the standard sharpen tool. In Photoshop Elements there are three controls called AMOUNT, RADIUS, and THRESHOLD and the equivalent controls in Paint Shop Pro are STRENGTH, RADIUS, and CLIPPING.

The way Unsharp tool works is by exaggerating the light-dark contrast either side of all the 'edges' making the image appear sharper. The RADIUS specifies how large the region around the 'edge' will be while the STRENGTH/AMOUNT is how much this region is adjusted (dark pixels made darker, light pixels made lighter). Lastly the THRESHOLD/CLIPPING defines when an 'edge' is considered to be an 'edge' and is acted upon.

Now, we need to know what values to put in these three controls. Everyone uses their own values and so it is really down to personal preference. However, the important thing is that we end up with an image that is sharp but has not been oversharpened and results in jagged lines. I tend to use STRENGTH/AMOUNT 50, RADIUS 0.3, THRESHOLD/CLIPPING 0 as a starting point but if you need more or less sharpening then increase/decrease STRENGTH/AMOUNT. If you intend to print your image rather than view on the monitor then you may need to increase the RADIUS control.

SAVE:
Lastly, we SAVE (FILE menu) the finished image. If the image is intended to display on the web then the .jpg format is recommended as it will compress the filesize by varying degrees. The higher the number that you enter then the more compression that is added and the smaller the file-size. It is just a matter of striking the right balance between a small file-size and an acceptable image for viewing on the internet/website. If you are using the image for other purposes and want to print it then try using a .bmp format which will not compress the image.

Remember to always keep the original files from your camera and back these up to an external Hard Drive, DVDs, memory sticks, and/or an off-site storage device such as the 'Cloud'.

This is just one method of improving photographs and many people have their own workflow. There are many more different ways to improve an image and certainly countless ways of sharpening an image. It is also worth mentioning that it is probably better to make all the above changes using LAYERS so that you always have the original image to fall back on. I hope this little article helps to inspire you to experiment with your photographs using Paint Shop Pro or Photoshop Elements.
















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