OP Home > Columns > Tech Tips > Taming The Skies


Tuesday, June 9, 2009

Taming The Skies

Bringing The Sky Down To Earth • Real Real-Estate Images • Extended Autofocus • Film Everywhere, But No Place To Process • Gauging Filter Effects

This Article Features Photo Zoom
tech tips
The sky in this image capture of Mono Lake, Calif., was far brighter than the foreground. I took three images from a tripod, each two stops on either side of what would be the correct average exposure. The three images were processed in Photomatix Pro software for an HDR image that now incorporates information in the sky and in the foreground. I used a Canon EOS-1Ds Mark II with a 15mm fisheye lens. The three exposures were 1⁄15 sec. at ƒ/22, 1⁄60 sec. at ƒ/22 and 1⁄250 sec. at ƒ/22. The ISO was set to 100.

Bringing The Sky Down To Earth
Q My true love is landscape photography and, in particular, I love sunset landscapes. One of the big problems I have in postproduction is optimizing both the sky and the land (and, sometimes, water). My typical approach is to process one or multiple files separately and attempt some kind of a complicated mask when combining them, but this rarely works to my satisfaction and almost always takes a LOT of time. I’m sure there’s no magic, easy fix (although I’d love it if you could share one with me!), but I’d truly appreciate any tips, hints or tricks you could share.
Jake Blanton

Atlanta, Georgia

A Actually, there are several ways to achieve optimum exposure throughout a high-contrast image, but you have to be ready at the outset. That is, you have to be willing to take enough captures of the scene (from a tripod) to generate all the needed exposures and then composite the images in postcapture software. As few as two captures will suffice if you have a bright sky and a reasonably lit foreground. In that case, you can easily composite the two images in Photoshop using the Blend If mode.

Blend If is so cool, it really could qualify as magic. First, from a tripod, capture two exposures of the scene in perfect registration—one properly exposed for the sky and the other for the foreground. Bring the two images into Photoshop, and then, using the Move tool, drop the dark layer on top of the lighter one while holding down the Shift key. The combined images become one image with two registered layers. If you’re in CS3 or CS4, you can assure that the two layers are in exact alignment by selecting both layers and going to Edit > Auto-Align Layers. Choose Auto Projection and click OK. Next, select only the top layer, click on fx at the bottom of the Layers menu (add a layer style) and select Blending Options. You’ll see at the bottom of the Blending Options menu a box called Blend If. Using the first of the two scales, labeled “This layer,” place your cursor on the black slider at the left and hold down the Alt (Windows) or Option (Mac) key. This will allow you to split the slider. Move only the right half toward the white end of the scale. You’ll see the two images on your screen blend together, the lighter areas becoming darker, and the darker areas becoming lighter. Choose the perfect combination for your image and taste. Once you’ve done this the first time, you’ll see how easy it is, especially compared to masking, which is a total pain.

Blend If works only for two-image composites. If your landscape has a wider range of contrast, even including a sunburst at sunrise or sunset, then you’ll need to capture more exposures to cover the full range, and you’ll need to use a different compositing technique called High Dynamic Range (HDR). This process is available in Photoshop CS2-CS4, but I prefer a program called Photomatix from HDRsoft. The blending options in Photomatix allow for optimal fine-tuning of exposures throughout your image, with maximum detail achieved in both extremely dark and very bright areas. Photomatix also offers a number of dramatic creative effects. Go to www.hdrsoft.com for excellent tutorials and demonstrations of this software.

With these two techniques, your photography of your favorite subject, the sunset, is going to rise to new levels in terms of quality and enjoyment.

Real Real-Estate Images
I take photos of homes for realtors. It’s a real struggle to get sharp images with good representation of room sizes. I’ve tried using my wide-angle lens, but it rounds out the corners of the photo, making the walls look like they bow. I’ve also tried getting low so one can see the floor and ceiling in the photo, but this makes the room look tall and skinny. I’ve been told I need to use a fisheye lens to get the shots I need. Do you have any suggestions?
D. Hinton
Via the Internet

A A fisheye lens is an extreme wide-angle lens. It will exacerbate the problem you’re experiencing with distortion of the image. If you really want to get serious about this, you’ll need to learn some new techniques and multiple-image compositing software.

If you’re using a D-SLR with an APS-sized sensor (1.5x-1.6x magnification), shoot your interior photographs with a lens in the range of 24-28mm. If your D-SLR is full-frame, a 28-35mm lens will minimize distortion. To get a more inclusive angle of view, you’ll need to take a number of overlapping images (from a tripod) and composite them using panorama-stitching software such as Photoshop Photomerge (www.adobe.com), Panorama Maker 4 Pro from ArcSoft (www.arcsoft.com) or Autopano (www.autopano.net), to name a few. The result is an extremely wide-angle perspective with minimal distortion.

Extended Autofocus
Will the new Canon EOS 5D Mark II autofocus with a 1.4x extender on a Canon 100-400mm lens through the full range of focal lengths?
J. Miller
Via the Internet

A No. The reason is that the auto-focus in the 5D Mark II shuts down if the light available through the lens falls below ƒ/5.6. Once you add a 1.4x tele-extender, which loses one stop, even the widest aperture of the lens (ƒ/4.5), less the one stop, takes you past ƒ/5.6. This is true of not only the 5D Mark II, but also the 50D, the 40D and the Rebel cameras. The pro cameras (such as the 1D Mark III and 1Ds Mark III) have an autofocus threshold of ƒ/8, so the autofocus would still work with a 1.4x tele-extender on these cameras. This is a real advantage when using the 500mm ƒ/4L IS and a 2x tele-extender (1000mm at ƒ/8), which I do a lot, handheld, for birds and wildlife.


Add Comment


Popular OP Articles