Sunday, October 27, 2013

Confessions of Image Blending

Alice Lake, Sawtooth Mountains - Idaho
Created using exposure blending.

Confessions of Image Blending

For many years I have used my trusted Galen Rowell split neutral density filters for probably 60-70% of all my landscape shots. They are, essentially, the ‘dodge and burn’ of a traditional darkroom - reincarnated into graded optical resin filters that many of us use so often for reducing the brightness of a sky.
Graduated Neutral Density Filters. Screen shot from Singh Ray website.
The split filter simply allowed a photographer to reign in the latitude of an image (the amount of bright highlights and deep shadows) so that a digital sensor, and ultimately a paper print, would be as natural looking to a viewer as the photographer saw it with his or her own eyes.

Split density filter in use - Thailand.

Exposure ‘latitude’ is the range of tones that can be reproduced without over or under exposure, and still achieve acceptable results. Traditionally, black & white and color slide film could successfully capture 7 stops of exposure (a ‘stop’ is a doubling or halving of the amount of light let in when taking a photo, or one f-stop change on the camera settings), color print film captured 5 stops, and new digital technology can capture 9-11 stops. The human eye, however, can process around 20 stops of latitude; with a combination of adjusting it’s iris and altering the chemical receptors.

So, where is this all going? If I was shooting a mountain scene and the sky was too bright, I would slide in a split neutral density filter (half gray and half clear) and adjust it so that the sky was darker. The problem with this is that the gradation fades in a horizontal line across the image, so any peaks or trees sticking above the horizon will instantly become darker, and may even become black in the final image. This works seamlessly for ocean scenes as, as we all can see by standing on the beach, the earth is flat – and the gradation works perfectly. But for mountain scenes, we have, over the years, just gotten used to the darkened protrusions above the horizon line. Galen Rowell, a master of ‘found’ mountain photography, helped create this filter system, and to look back at any of his award winning images, you can clearly see the darkened details within the filtered area.

Enter Photoshop and the modern high megapixel camera.

For the past two years I have not used my split filters – even once. I love them, and cherish them, and take great care of them – but find that I can achieve much better results in the post processing session than I ever got with the filters. How could this be? Is this just satin speaking through my damned husk of a body? Have I no soul left at all?

For the holy sanctity of simplicity, lets start at the ocean – a nice stretch of Kona coastline at dawn - the pulsing heartbeat of the earth, where one's digital sins are washed away with the gentle flow of water and sand.
RAW image, exposed for foreground.

RAW image, exposed for sky.

There are billowy pink clouds on the horizon and the waves are breaking with a nice aquamarine light. Normally, I would have used perhaps a +3 neutral density filter and brought down the sky to a reasonable brightness – not now. I want to keep that silvery bright line on the horizon, and maintain the little highlights in the clouds. I adjust the exposure for the foreground and shoot a test. I check the histogram on the back of the camera to make sure I am not clipping the image in the shadows, and then do the same for the sky, making sure I am not clipping the highlights. I then go back to the foreground settings and take an image, quickly adjust for the sky, and take another. I now have two images, captured within a second of each other, that are identical except for exposure.

This method does require some practice, and a certain degree of expense. You must have a rigid tripod with a bombproof head. I use Benro carbon fiber legs and a heavy Manfrotto 468 hydraulic head. When set, this will not move unless struck by a small rhino. And yes, this is the set-up I carry with me at all times. One item to note for this scene – sand moves. Each time the waves surround your tripod legs they will shift and sink just a tiny bit. I suggest that when you find the spot you want to shoot from, plant that tripod with gusto, and then let the waves come and go. Eventually the tripod will find its place and settle to a stop.

Concerning the ocean scene in question, there will be movement in the water between your two images. The clouds, however, will not move perceptively. This will be managed later.

Once you are back home you will open both images in Lightroom or Camera Raw. You will simultaneously adjust both for lens correction (if desired), chromatic aberration, clarity, and color balance. Then, one at a time, you will adjust the exposure for whichever image you have displayed. In the sky version, don’t worry about what happens to the foreground, and in the foreground version, don’t worry about the sky. Remember that the sky, in nature, is almost always lighter, and to darken it too much will produce an unnatural photo, quite like an HDR image.

I then save them both, and open them both at the same time, in 16 bit, in Photoshop. Now it is time the blend the images.
Both images opened in Photoshop, after RAW processing.

Split the screen so that both images are displayed at the same time. Then grab one image, say the sky, and drop it on top of the foreground. They will find their own edges and will be overlapped perfectly. Now, if your tripod had absolutely no movement whatsoever, there will be no problems from here on. If there was, then there will be some work to do, or the image may just be unusable (another reason to take multiple photos while on location – flash memory is cheap).

Close the file that you will not be using and let the blended exposure go back to full screen.

This is what you see - the darker image (correct exposure for the sky) now covers the lighter image.
Now choose the eraser tool and make it really big, with fuzzy edges. Here is where a steady hand comes into play. I start with 100% erase, and totally ‘paint out’ the lower part of the image. As you do this, the lower, correctly exposed foreground shows through. As you get closer to the horizon, I back off to about 60% and shrink up the brush size. Don’t try to make a fine line between the two exposures – it will look artificial. The sky is always lighter at the horizon in nature - so let some of the erase rise above the horizon line.
Start erasing the top image to allow the correct foreground exposure to show through. The area in the lower right corner has been erased to show the layer below. 

Once you have a blended image that looks acceptable, and natural (remember that you are trying to reproduce what you saw that morning) merge the visible images into one and rename. Now you have the starting point for the rest of your workflow, one with wide latitude and yet well within the parameters of printing. Instead of the sky being taken down with one solid curtain of grey resin filter, you can paint, in or out, depth and contrast from the actual full-color scene.  Now adjust as normal: crop and straighten first, adjust color balance if needed, adjust levels or curves (with or without masks), saturation, contrast, etc.
The finished blend - still some work to be done.

This process my sound complex, but once you get the hang of it, it really goes quite quickly. And even though this example was for a flat horizon, the mountain scenes turn out dramatically because the points of peaks and trees can be allowed to show through an overexposed sky.
The finished image.

I recently sold my entire set of split neutral density filters and am not looking back. I loved them, but hey were just six more things to carry around, to keep clean, to worry about. Now, I just make damn sure my tripod is stable (rhino-proof) and shoot away. Some images need very little blending, and some benefit from complex blending at the extreme end of the artistic scale – but all, I feel, are superior to the filters.

Saturday, October 26, 2013

Fotodiox Pro Filter Adapter / F-Stop Loka Bag

Kathryn Lake, Sawtooth Mountains - Idaho. 14mm, with circular polarizer.

Fotodiox Pro Filter Adapter / F-Stop Loka Bag  

It’s been a while since I had time to slip in some comments here on this blog, or anywhere for that matter, since last spring. During that period of time, when I was laid up from a ski-injured knee, I managed to eek out a few ripe photography pearls, and an odd article here and there for magazines. However, once the knee was healed, it was back to work as usual, and my entries here died on the vine. So, without further adieu, I would like to briefly talk about the Fotodiox Filter Adapter for the Nikon 14-24mm lens, and the F-Stop Loki camera pack.

When I changed over to the Nikon D800, paired with the Nikon 14-24mm lens, I was terrified by the dome of crystal that bulged from the front of the barrel. Thankfully, I have learned to love this lens, and find myself less anxious about the optics - having learned some basic protection skills, and discovering the real value of the Fotodiox adapter.

For $249 I have seamlessly integrated the occasional need for a circular polarizer and the often-needed lens protection factor. The build quality, materials, and optical clarity of this simple kit took me quite by surprise. The f/2.8 14-24 ED lens has a magnificent field of view, and I was nervous about vignetting – no problem. It is such a heavy lens that the added weight of the adapter doesn’t really make a noticeable difference.

Vignetting was my primary concern as the corners of the 14-24mm are very sharp. I didn’t want to loose my full frame view due to soft, and perhaps dark, corners – which would require a post process crop. To my delight, there is no vignetting with this filter adaptor – even with the filter in place. I sometimes correct the lens distortion in Lightroom, but even if I don’t there is no appreciable vignetting.

I was mostly concerned about using the polarizer during mid-day, with lots of sky. Images captured in shade, containing moving water, are a simple thing – adjust the tripod, twist the polarizer to see ‘into’ the water, and click! But broad daylight with sky – that is usually a recipe for disaster. Typically, a polarizer will only darken a narrow portion of the sky, leaving the final image with an unnatural dark blue wedge in the sky. Additionally, you may not even see this in the LCD screen, on site – but may only discover this bizarre sky tragedy when you are at home, all cozy, and viewing RAW images on the 30” Apple monitor.

Somehow, while I was shooting in the springtime desert world of Canyonlands in Utah, I did not get this ‘death wedge’ of dark blue sky. In fact, I got tonally pleasing enhanced skies at even 14mm! I am unsure of the why’s or how’s, all I know is that I used the polarizer at 1pm (the death zone) and got images that were more than acceptable, in fact, they were quite good.

The Dollhouse - Canyonlands, at 14mm.
The polarizer produced no problems with the sky.
 The filter adapter was mounted onto my camera for about 50% of the 7-day expedition. Only a fraction of the time was the circular polarizer in place. The gigantic 145mm lens cap was in place 100% of the time while it was mounted. Not only does the adapter give you a little more flare reduction, it also gives you some cushion while climbing through slot canyons and dodging the occasional willow snap-back. The lens cap is robust, and never came off without my work to remove it. Even if, somehow, an errant branch were to dislodge it, there is no way on earth you would not know it had hit the ground – think of dropping a Frisbee made out of Melmac – the dinnerware of the 50’s (polyoxybenzylmethylenglycolanhydride).

Fotodiox also sells split neutral density filters for this adapter kit, but I have become very comfortable with image exposure blending in Photoshop and have found no need for these extra on-site optical tools.

Fotodiox has produced an amazingly engineered lens hood/adapter/circular polarizer for the boutique Nikon 14-24 lens. If NASA was creating delicately milled aluminum components for the optics of a Jupiter probe, I like to think that this is what it would look like.

F Stop Loka. Petrified tree roots, The Maze, Canyonlands Utah.
The F Stop Loka camera bag was another joyous discovery through Trey Ratcliff’s website, “Stuck in Customs”. At 37 liters (2250 cubic inches), this pack is perfect for an entire day on location with all of my gear. And by gear I mean: Nikon D800, 14-24mm lens, 24-70mm lens, 70-200mm lens (the holy trinity), shutter release, Fotodiox Filter and polarizer, batteries, memory, cleaning cloths, business cards, etc. and – water bottle (or bladder), food, rain jacket, ski hat, gloves, fuzzy jacket, personal locator beacon (PLB), sunglasses, minimal climbing gear (mostly for anchoring camera bag to a wall), and my carbon fiber tripod. This backpack, including the Internal Camera Unit (ICU), weighs about 3.5 pounds.

Screen Shot from

The ICU is one of the most unique features of this professional level camera pack. When you purchase the pack, you also have to choose the internal container for the camera gear. Without the ICU, you would just have a large empty daypack – not a bad thing, but that is not why you dropped $330. The ICU’s come in different sizes and shapes, and hold varying amounts of camera equipment.  The “Pro Large” was my choice of ICU. These padded ‘cubes’ of nylon dividers and Velcro straps stuff into the backpack and lock into place with Velcro tabs. Now, here is the best part – to access the contents, you zip open the part of the backpack that lies against your back. Different, huh? Usually you throw your pack into the snow or dirt with the shoulder straps facing down, which gets them all wet or nasty. Not so with the F-stop. The engineers there have put a lot of thought into the design, and decided to have you place the waterproof back panel of the pack into the snow and dirt – not the shoulder straps, brilliant!

The size of the Loka does not allow for overnight hikes, but F Stop makes a much larger version, the Satori, which is a 62 liter pack and quite capable of lightweight overnight exploits. For multi-day adventures I still use my tried and true set-up – years in the making, which will be the discussion for a later blog.

It is a little difficult to explain how this pack works, so I will suggest going to the website and watching a few of their videos. I can honestly say that this is the best camera bag I have ever owned – weddings, model shoots, street shooting, skiing, mountain and desert canyon day trips – it just works so well. Super rugged, well designed and manufactured, this pack has totally replaced almost all of my old Lowepro bags (which I thought would never happen).
Whispering Stones, Kona Coast - Hawaii.