Photo Shooting, Photo Shopping

The Dilemma: There have been volumes written about Photoshop's impact on the credibility of our digital images. Certainly, Photoshop has been loads of fun to play with, and can produce some amusing results as seen in this assignment I gave in one of my classes.

In are recent post, David Hobby reminisced about some of the many techniques photographers used during the pre-digital days to tweak their exposures under adverse conditions. For me, there is one paragraph that was particularly meaningful, and I quote:

"... the limitations of this physical darkroom process is also what set our ethical limits when Digital Photoshop arrived. If you could have done it with an enlarger (dodging, burning, tonal adjustments, etc.) it was ethical. If not (cloning out a Coke can on a table or a power line behind a head shot) it was not."

This reflected my own opinions concerning the line between an "enhanced" image and a "doctored" one. Mr. Hobby's Big Three Enhancements (Dodging, Burning, and Tonal Adjustments) are pretty self-explanatory, and in my mind are appropriate for insuring that significant detail is maintained in the highlight and shadow areas.

The Shot: This shot was taken at the San Mateo County Forensic Laboratory. My editor wanted a shot of the Laboratory Director, along with some staff members, taken in the lab. I wanted to provide a good sense of the lab environment with lots of high-tech detail. While this may not be as sexy as CSI Miami, this is the real deal, and these gentlemen are the scientific muscle behind law enforcement within the county. The details? Nikon D7000, ISO 200, Flash White Balance, and 2 SB-800s as Remotes shot through a Zumbrella at a height of 9 feet with a third shoe-mounted SB-800 serving as Commander. I was standing on an elevated platform, looking down. Exposure was 1/80 @ 5.6. The lens was a 11-17 Tokina, set to 13 mm. I normally crop much tighter, but decided to leave some space to correct the wide angle "stretch face" that was occurring near the corners. I purposely employed a loose crop so I'd have extra image space to work with.

 

When using Perspective correction, you are going to lose some real estate in the corners. For those who are making these corrections, you'll want to cut your loses and keep as much of the image as possible (and assuming that that the image is level) Try this:

• Crop the image to an 8 X 12 aspect ratio, keeping as much of the image as possible. When using a DSLR with an APS-sized image, you wil find this aspect ratio a nearly perfect match, so you can potentially retain the entire image.
• Turn on the Viewing Grid to "on".
• Using the Perspective tool, draw the upper corners until the are re-positioned one-inch inbound on both the left and right sides.
• Accept the changes. 
• Change the Crop aspect ratio to 8 X 10, and crop.

Your image will now be a perfect 8 X 10 with a minimal loss of surface. 

 

Some additional cropping was used to minimize the effect of those distracting boxes on the left and right sides. While the converging lines of the back wall are reasonably parallel, the table is still "strained" due to the oblique angle at which the photo was taken. Looking on the bright side, who wouldn't want to work in laboratory with rhomboid-shaped work islands?

Conclusion: I contend that this use of Photoshop is still within the boundaries Mr. Hobby described, since the same effect could have been achieved in a conventional darkroom by tilting the easel (the frame that holds the printing paper) before the exposure is made. Had I been printing an identical negative to this sample, I would have adjusted the easel so that the top edge of the image was closer to the enlarging lens than the bottom. If you were lucky, a smaller aperture setting on the enlarging lens would provide the depth of field necessary to render top-to-bottom sharpness. I remember at least one enlarger that had a tilting lens board for use when this very type of correction was required. 

I hope this makes my case for using perspective adjustments for images that must be taken from angles where such visual distortions occur.

Plane Of Focus

Here's a photo, taken at Carnaval in San Francisco, that should be consigned to the Recycle Bin. It could have been a great shot, if it wasn't so "blurry". But if you look closely, you can see that some parts of the image are quite sharp.

On closer examination, we find that there is a Plane of Focus where the details are sharply rendered, Unfortunately, it is position about four feet behind my two intended subjects. The image failure was due to improper focus, not a lack of depth of field.

Focusing Brackets: In the viewfinder of a typical DSLR you will see pairs of Focusing Brackets. The number will vary from three (Nikon D40) to 51 (Nikon D4). Individual pairs of brackets can be selected, giving the user to options to determine exactly where the plane of focus will be. Additionally, you can select which pair of brackets will be active, which greatly increases our control over the situation.

I typically opt to use the central pair of brackets, and shoot in the Single Servo mode. I choose the central pair because they are the most sensitive to variations in contrast, and are therefore the best choice for critical focusing. This means that when the shutter release is partially depressed, the lens will sample the scene, near to far, until sharp contrast is obtained within the selected brackets. Once this optimal contrast is determined, the camera locks in the lens at this point of critical focus. When the shutter release is pressed all the way and released, the camera records the image.

In this simulated look through the viewfinder, you can see the Focusing Brackets positioned on the Elmo hand puppet, which happens to be in the center of this composition. Because of Elmo's position was centered in the frame. I was able to simple depress the shutter release until the exposure was made.

Off Center Point Of Interest: The blind "compose and shoot" worked for the Elmo image, but what if the center of interest in not centered? This next example illustrates that very point.

If you examine the image, you'll see that the physical center is located beyond the glass walls of this terrarium. The solution would be to:

• Recompose the image so that the focusing brackets and the center of interest coincide, 
• Partially depress the shutter release to lock focus, 
• Return to the original composition, and 
• Fully depress the shutter release to make the exposure.

This is a simulation (rough) of the re-framing sequence in Bullets #1 and #2. When you return to your original composition, you will see that the focusing brackets are no longer on the center of interest. Since you locked in the focus at Bullet #2, your focus will not shift, provided your camera is set to Single Servo as I suggested earlier. At the moment the shot was taken (Bullet #3), the viewfinder probably looked something like this:

This works for single shots, so the sequence (Bullets #1 through #4) must be repeated for each subsequent shot. Or does it? 

AE-Lock, AF-Lock: Nikon DSLR cameras have a button conveniently located to the right of the eyepiece that is user-programmable and marked, "AE-L AF-L". (Click here for a detailed description). To address this problem, there are two settings that might be of interest:

• AF Lock Only: If you select this mode, you first allow the camera to focus itself (using the focusing brackets of your choice) by partially depressing the shutter release. Once focus has been established (I program my cameras to "beep" softly when this happens), you hold the AE-L/AF-L button down and start photographing. The focus will not change until you release the AE-L/AF-L button.

• AF ON: If you select this mode, the autofocus will be activated only when the AE-L/AF-L button is simply pressed. When you release it, the camera not change focus. Adjustments can be made by additional presses on the button

I personally prefer to leave mine set to AF Lock Only. I usually leave the camera set to Single Servo so that focus is taken, then immediately locked, so I can re-frame the image any way I choose.  In actual use, I would perform bullets #1 and #2, and once focus is locked I immediately hold down the AE-L/AF-L button. So long as my subject doesn't move, all of my subsequent images will be in focus, so long as I keep the button pressed.