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SEEING SPOTS

#1 in a series of articles on finishing images prior to printing.

PLEASE REMEMBER TO CLICK ON THUMBNAIL IMAGES TO SEE THE EXPANDED VIEW.

Water and dust spots can ruin your outstanding images. In this case I was sheltered in my car with my camera on a tripod. Blowing mud spray from Chocolate Falls covered my camera lens. It would not have been worth staying outside. I am not sure what got scared out of the visitors who found refuge by the vault toilets that were hit by lightning in this shot. Likely, the were scared $4!+less. 

There are lots of tasks to complete before posting or printing an image. Making sure they are free of distracting dust spots and other blemishes is on that list. Seeing spots on your photos, especially after they are printed is not fun! It is especially not fun if you discover a spot just as you are hanging a piece in a gallery or delivering a “finished” print to a client. This article covers the common spot issues and what to do about them. 

So here are the main kind of spots we see:

Dust spots (some call them dust bunnies).

Water spots

Hot spots

Dead Pixels

Dust Spots & Water Spots

Dust spots and water spots occur when there is dust on the sensor, on the inside elements of your lens or on the outer surface of your lens. They do not have well defined edges and are multiple pixels wide. They are going to happen if you shoot in adverse conditions, such as in a dusty area (think sand dunes and slot canyons) or wet area (think rain, misty waterfalls or breaking waves). Dust spots have a darker center and blend gradually to the outside. Large water spots have clearer centers like those n the above image, whereas clean water spots are fairly clear (arrow). 

The best thing you can do to minimize these spots on the sensor or the inside of the lens is to never change lenses in these conditions. Since that may not be an acceptable alternative when you need that other lens length for a stellar composition, learn to change lenses in the safest manner. Hold the openings out of any wind or moisture, including updrafts as you change lenses. Also, vacuum out your camera bag periodically and keep both front and rear lens caps on when the lens is not in use. For photographers who go on extended trips, it can be quite difficult to avoid dust spots. So a section below will describe how to fix them.

If the front of your lens is very clean, you can determine the location of offending spots by shooting multiple images of the sky. Change lenses and do the same. If the spot is still in the same location, you have dust on the sensor. If the spot is on the sensor, the spot will remain in the same place. If it is on the inside lens element, the spot will disappear with a lens change. First try holding the lens or camera with the open area pointed downward. Use a gentle stream from an air bulb and hope gravity allows the offender to fall out. If this does not work, the spot may be fixed. In this case you should use a sensor cleaning kit or lens cleaner to remove the spot. This can be tricky with sensors and camera shops usually do not charge too much to clean your sensor, so consider using the pros. 

For the outside of the lens, a lens brush is the first choice. Then use lens cleaner (not glass cleaner that can dissolve lens coatings) and a lens cloth to remove fixed dust or water spots. 

Reduce water spots by keeping your lens cap on until ready to shoot. Use a lens hood and either a hat or umbrella over the top of the lens. Umbrellas aren’t recommended when lightning is possible. but camera mounted mini-umbrellas are a good alternative. If you are in ocean spray, fog or waterfall mist, you will have to dry your lens frequently. A microfiber cloth is the most effective way to do this. Be gentle! Carry two or three cloths so you always have a dry one!

Hot Spots & Dead Pixels

Hot spots occur most frequently during long exposures and are especially visible in dark or underexposed areas. They occur from overheating in your camera. Some cameras are more susceptible to hot spots. Dead pixels are areas of the sensor that are unresponsive. Hot spots will be in different locations from image to images, whereas dead pixels will recur in the same spot. You are not likely to have many dead pixels and a few are easy to deal with. When buying a new or used camera, always take a few test shots, preferably of a solid color, to evaluate for dead pixels. 

With some sensors, you will may a screen pattern in greatly underexposed areas when you try to bring the exposure up from black. The primary solution for this is to leave the area solid black. Thid does not meet the goal of most landscape photographers who want to see detail in the black areas.  

 

 

 

The image was taken in the evening. That morning I had changed lenses while shooting sand dunes. Many landscape photographer who spend weeks on end on the road do not have the opportunity to clean their gear properly. The result is shown in this raw image. I knew this image was a keeper despite hundreds of spots that showed in the sky. I chose to make most of the edits prior to fixing the spots.

Click on each of these images to see the enormous number of spots. I used the technique described below under "Fixing Water Spots & Dust Bunnies" to better visualize the task before me.

Should you fix spots early or as a last step?

You may choose to fix spots at an early stage of processing to determine that the image can be salvaged before spending a lot of time on it. Also, if you fix spots prior to other changes, you can synch those fixes with all images that are going to have those spots, as would be the case with sensor dust or dust on the inside of the lens. When the spots looks excessive, but the image is good such as the lightning at Grand Falls at the top of this article, try a few spots before putting any effort into processing the image.

The alternative is to make sure the image is worth the considerable time you might spend removing spots. This is the way I work most often when there are lots of spots, but not when I have a nearly impossible image. I complete most of my changes before deciding whether to remove dust spots. An additional reason for this is that enlargement of the image may introduce newly apparent spots, so if you are going to print the image, you should go back and check for spots later anyway.

 

Click on each image below for a better view of the changes.

In the outlined section from the image above, you can see a small dust spot that occurs on an arced section of sandstone.

When using the Heal/Healing tool in ACR there is an attempt to select the most similar area to copy. Because of the converging curves, there is no area that really matches, therefore the result would be unacceptable.

This repair was done with the healing brush in PS. In this case there is a problem not just matching the converging lines, but the lines get blurred if the brush is feathered. If the brush isn't feathered, it will be more apparent that the lines don't match.

When uising the Selection Lasso Tool, then choosing Edit/Fill/Content Aware fill option provided in PS, the results are again unsatisfactory with blurred areas and unmatched lines.

The result of using the Content Aware Tool is an area that does not match well, including the feathered area on the borders of the selection.

The best option takes more painstaking work using the Stamp Tool on Normal setting. Start with the tool much smaller than the area to be repaird and make selections from matching areas. When done with the stamp tool, you will likely need to add contrast and texture to smaller areas using the Brush Tool, Dodge and Burn Tool or an even smaller sized Stamp Tool.

Fixing Water Spots & Dust Bunnies

These defects can be large. If they occur in the sky or on a solid area such as a lake, they are easier to fix than if they are in an area with lots of detail. 

My go to fix is using the healing brush tool in either Lightroom or Adobe Camera Raw. Adjust the size of the brush with the bracket keys “ [ “ or  “] “. I recommend a feather of at least 50 and and opacity of between 80 and 100. To change the feather hold down the Shift Key while using the left or right bracket. Always have the brush size large enough that the non-feathered area covers the entire spot (if the spot is round). Be aware that a feather will have the effect of blurring the area of the feather. This can make your changes look unnatural. If the spot has length to it, you may drag the healing brush across it or hold the shift key after the first click, then click on the opposite end of the spot. This will give you an elliptical brush of the length you choose.

When removing multiple dust spots in smooth areas such as the sky or a lake, my preference is to use Adobe Camera Raw.

Create a duplicate layer (Command or control J)

Open the image is ACR

Adjust the following sliders: 

Exposure +1.00

Contrast +20

Dehaze +70

You will now see the spots more clearly. Note that I do not click “Visualize spots” as this misses a lot and can mislead you into correcting areas that are normal small highlights. I do click on Visualize Overlay. This allows you to move the circle that the healing brush  selects as its source. Simply click and drag to a better location when necessary.

When done with corrections, double click on Exposure, Contrast and Dehaze to bring them back to “0”. THIS IS IMPORTANT! IF YOU DON’T DO THIS, YOU WILL HAVE TO START ALL OVER AGAIN! If there are extensive spots, you may want to close out of ACR, save the changes, merge that newly created layer down and then copy your merged layer to a new layer for additional changes. Repeat as many times as necessary. 

For large spots that affect details in critical areas I stay in Photoshop using the technique to remove unwanted objects. Use the Lasso tool to select an outline of the area. Then go to Edit/Fill. Set Contents=Content Aware and Blending Mode = Normal. See if this works well. If it is inadequate, I will use the stamp tool on Normal mode to fill in parts of the area.

Fixing Hot Spots and Dead Pixels

Dead pixels are simply a small dark or colored spot. Hot spots can be a variety of colors and are usually cross shaped with a brighter pixel in the center of the cross. Again, I use the healing brush, but this time in a much smaller size. First duplicate your layer or create a new layer. This is so you can remove these changes easily in case you make a mistake without noticing, such as dragging a big line across your image. View your image at at least 200% but 300% or more might work better for you. Then scan across the image slowly. Pixels that need correcting will jump out at you. Select the Healing brush tool on Normal mode. Set the hardness to around 78-80% using the drop down menu adjacent to the brush size on the upper left. Click and hold down while moving across the spot. Alternatively, you may use the Stamp Tool in Normal mode. Select a small area (usually a dark area) close to the hot spot and Command Click (Mac) or Control Click (PC) on that area. A small cross will show the area that the correction is selected from. Continue scanning back and forth until you are sure you have everything. This may take a couple of passes.

Areas that have arced lines can be particularly troublesome. Using the healing brush will try to select a similar area, but the arcs will not match leading to jagged arcs. In this case use a much smaller stamp tool to fill in the spot from areas that match those smaller areas. To complete this more time consuming repair, you may need to add texture, lightness or darkness to small areas of your repaired area. You can do this with the burn and dodge tools, the stamp tool and the brush tool in PS.

This is a detail view of the image shown above. In addition to all the dust spots in sky, there is a very large sensor dust spot on the brain rocks (arrow). Fixing this spot required multiple uses of the stamp tool to recreate the missing rock structure.

Images that have smooth water will need to be examined closely for both dust spots and hot pixels. This was a six second exposure which made hot pixels more likely.

Using the technique described previously to better visualize spots in ACR, small hot pixels were seen (click on image to enlarge). A 100% view is not adequate to see all these spots.

Enlarge your images to 200% or 300% to better visualize the spots. They are easily removed with the Healing brush in PS. While this may seem unimportant if you only post on the web, it is essential for big prints. Handling the noise pattern shown in this image will be discussed in a later article.

Fixing Hot Spots and Dead Pixels

Dead pixels are simply a small dark or colored spot. Hot spots can be a variety of colors and are usually cross shaped with a brighter pixel in the center of the cross. Again, I use the healing brush, but this time in a much smaller size. First duplicate your layer or create a new layer. This is so you can remove these changes easily in case you make a mistake without noticing, such as dragging a big line across your image. View your image at at least 200% but 300% or more might work better for you. Then scan across the image slowly. Pixels that need correcting will jump out at you. Select the Healing brush tool on Normal mode. Set the hardness to around 78-80% using the drop down menu adjacent to the brush size on the upper left. Click and hold down while moving across the spot. Alternatively, you may use the Stamp Tool in Normal mode. Select a small area (usually a dark area) close to the hot spot and Command Click (Mac) or Control Click (PC) on that area. A small cross will show the area that the correction is selected from. Continue scanning back and forth until you are sure you have everything. This may take a couple of passes.

Being thorough with your spot corrections is essential for fine art prints. Knowing how to use all the tools available to you will help you in the process. In the next issue we will describe how to fix lens created chromatic aberrations and exaggerated horizon lines that often occur in post processing.

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