For every photographic problem that might be addressed at the time of shooting, there always seems to be someone’s glib response that you “can fix it in post.” It is indeed possible to do many things with Lightroom, Photoshop, or GIMP – but is that the best or easiest way to do it? Let’s examine nine common correction operations, how they play out when shooting or in post, and which seems to be the better (or at least most efficient) option.
1. Perspective correction and leveling. Using a wideangle lens (<35mm) at anything but a dead-level position causes converging (or diverging) verticals. In the dark days before Photoshop, converging verticals were mitigated with PC lenses that shifted the lens relative to the film. This shifted the horizon and the effective viewpoint of the camera (10mm of shift compared to a 24mm frame height can move the horizon line more than 40% up or down). Older shift lenses had larger image circles to accommodate this, but they also show chromatic aberration on digital sensors – and they required inconvenient stopped-down operation for viewing and then metering. Newer lenses have electronically controlled apertures that help compensate for some of this. Correcting converging verticals in post-processing avoids the optical compromises and difficult metering, though the “warp” to the frame (which goes from rectangular to trapezoidal) cuts down the frame size, changes the effective aspect ratio of the picture, and compromises fine details if you’re starting with a low-res file. But the bigger problem is that most programs are not really capable of correcting perspective issues without distorting the vertical/horizontal proportions of the picture – generally making things look too tall. DxO Viewpoint has a ratio corrector, but it still requires visual estimation of a viewing angle that you never saw in real life). In terms of misery level, the easiest option is to get a wider lens, get as close as you can keeping the subject level, and simply crop as necessary. Time of shooting.
2. Vignetting control. Older lenses, especially symmetrical ones, often exhibit darker corners on digital sensors (they did on slide film as well, but on the negative film that most people used, this was less visible). Vignetting is a limitation imposed by physics. It also occurs with lenses designed for digital, but in many cases the camera can automatically compensate for a known lens when generating a JPG. At the time of shooting, when generating a RAW file, you basically have only a center filter as a choice. These very expensive filters impose big losses in terms of film speed (typically requiring 1.5x the exposure) and work best at smaller apertures. Even where there is no Lightroom profile for your lens, other solutions such as CornerFix and Adobe Flat Field allow you to shoot control pictures for repeatable corrections in the future – and to shoot with no exposure increase. Post.
3. Fill light. There are those who profess never to use flash and only whatever light is available. No one knows what they do with pictures that exhibit dark eye sockets, awkward shadows, and dominant light sources that point the wrong way. You can fix some of this in post, but simply the raising the exposure in certain parts of the image can make it difficult to maintain a natural-looking result. The major solutions here are to compose to face the dominant light source, use a reflector, or (heavens forbid) use fill flash. Time of shooting.
4. Light balancing (cooling). Low incandescent light provides unique challenges for digital sensors, almost all of which have noisy blue channels. Room light is typically pretty low, and the ISO setting on the camera typically ends up being pretty high, which means more noise across all channels. Using white balancing to compensate for reddish incandescent light exacerbates the problem in the blue channel by amplifying it even more. If you have a steady enough hand to do it, using a 80A (KB-15) filter drops the red and green channels so that the noisy blue channel is not unduly amplified. You lose 2/3 of the light doing this, but it cuts down on chroma noise. Time of shooting.
5. Light balancing (warming). The red channel does not suffer from the noise issues that the blue does. So it is ok to amplify it later. This in itself is not too compelling, but consider how at the time of shooting, warmer, no matter how warm, seems better – and yet in editing, things often look too warm. So consider limiting your filter filter use to an 81A (or KR3) and do any additional warming later. Post.
6. Red enhancement. The didymium red-enhancing filter has largely gone out of production (possibly due to demand and possible due to RoHS considerations). Its effect, which is to suppress “every other color” in the red-yellow range and then everything else past it, is extremely difficult to reproduce in post, if only because the peaks and valleys, occurring every 25nm or so, do not correspond with available adjustments to color in Lightroom (many of these actually fall between colors). Although it might ultimately be possible to reverse-engineer the effect, it would be a pain… Time of shooting.
7. Graduated neutral-density filtration. In color work, at the time of shooting, your only real choice to make the sky darker without a polarizer is a graduated neutral-density filter. The best versions are rectangular and allow you to rotate and move the horizon line. That said, they are much more unwieldy and flare-prone than circular grad filters, which are compact, easy to use, but completely inflexible in horizon line (midpoint of the gradient) placement. And with either, the hardness of the gradient needed is defined by the lens in use (oddly, only the rectangular versions offer a choice of hardness). Longer lenses require a harder cut. Provided that the dynamic range your scene permits it, the better solution is using gradient filters in Lightroom. These are variable for center position, rotational angle, and steepness of the gradient. In fact, they can be combined with other adjustments. The quality loss is minimal for simply darkening part of a scene; usually it is a relatively detail-free area like the sky. Post.
8. Specialty filtration. Softeners, diffusers, cross-screens, diffractors, and the like are filters for which there is no good Photoshop equivalent (assuming, of course, you are into the looks these filters create). Time of shooting.
9. Black and white tone adjustment. If you are into the effects of colored contrast filters on black-and-white film, you cannot very easily bolt such a filter onto a camera with a Bayer filter, because some filters (particularly red) can cause havoc with demosaic-ing. The Channel Mixer function in Photoshop (and Lightroom) lets you selectively raise or drop colors (at least within -20/+20) without too deleterious an effect on the image. The sole exception is the Leica M Monochrom, which having no color data to work with, must be filtered at the time of shooting. Post.
10. Correcting mixed lighting. Balanced fill flash falls apart any time that a flash is being balanced against something with a different color temperature. The most common problem is in room light, where at base ISO, flash essentially becomes the only light source, making the subject bright but the rest of the frame relatively dark. Raising the ISO tends to even out brightness, but it leads to pictures where the background is yellowish and the flash-lit subject looks normal. Although this can be corrected with a lot of work later, the easiest thing to do is to gel the flash with an 85A filter to make its light the same color as the room light. Time of shooting.
None of this is to say that there is anything wrong with post-processing digital images, and in fact, some things can only really be done digitally (fine-tuned and synchronized white balance, distortion removal, sharpening, etc.). But it is to say that a little more care in shooting can cut down on the time and frustration involved in post-processing.
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A long introduction
It’s a little bit difficult to understand why Leica and Metz have such a strange relationship. It is no secret that Metz makes Leica’s flashes, but it is surprising that when it comes to the SCA system and TTL operation, Metz is just as much a stranger to Leicas as it is to Nikons.
The Metz 45, like the Vivitar 283, is one of the most timeless flash designs that exists. Since the 45CT-1 of the late 1970s, Metz 45 series flashes have been the gold standard in light output. automatic flash exposure accuracy and light quality (meaning that the diffusers actually work, and the light has a nice warm tone to it). The massive 6 x AA battery pack and solid bracket add to the fun. These are flashes that mean business.
But since 1979, Metz has leaned heavily on modules rather than dedicated flashes. It actually did a remarkable job in adapting the 45 CL series to TTL cameras, and there was a module for every application, and for good measure also slave modules and even basic hot shoe modules. Digital, however, has presented its own challenges. Digital “TTL” systems actually do look through the lens, but they typically look at preflashes rather than cutting off the main flash. Because the architecture of the 45 series did not allow for multiple flashes in a cycle (also necessary for High Speed Synch), Metz introduced the 45CL-4 Digital, which has that capability.
The 45CL-4 Digital functions like a 45CL-4 in most ways. You need to add an SCA3000 connecting cord and your choice of SCA3000-series module to get TTL operation on a film camera. Automatic operation requires nothing but a PC cord. But to get E-TTL (Canon), i-TTL (Nikon), and GNC (Leica), you need an SCA3045 connecting cord and one of the latest generation modules (M10 for Nikon; M5 for Leica). If the title of this post seems complicated, that’s because connecting all of these things is.
The strange irony is that using older modules leads to additional (but erratic) functionality, all of which revolves aroud HSS (high-speed synch). A Nikon M8 module with a D700 will high-speed synch some of the time (but only, it appears, at 1/1000 sec and faster). A Leica M3 module with the M typ 240 gives you high-speed synch sometimes – but most of the time just shoots off a full-power flash blast. The newer versions don’t allow HSS. When I pressed Metz on this, I learned, at least for the Nikon, that the HSS synch protocol changed between the film and digital Ms, and that it’s just a coincidence that it works. Yikes.
But back to our story. The SCA 3045 M5 on the M typ 240 gives you GNC (Guide Number Control), which is a limited form of M-TTL. It shoots a pre flash, measures it, and then shoots the main flash. Although some deride it as not being “true TTL,” it is conceptually identical to how all M-TTL flashes work. The only catch is that it is slower between flashes and lacks exposure compensation capability. When the “GN” switch is set on the module, a green light on the module glows (odd – because the same module doesn’t do that on the 54MZ-3).
A short statement on performance
Let’s say this: it works. Automatic modes are generally accurate (if slightly underexposed – which is ok for digital), and GNC is right on the money.
The GNC system does not seem to be fooled by sun in the frame (likely because the Leica TTL sensor is too primitive to see things off x). The double flash should be fine for all adult subjects; children may react to the pop-pop and blink. Contrary to the instructions, the flash does work with GNC with bounce and/or the use of the secondary reflector (as seen in the shot above, which is even more remarkable considering that it was taken in a stainless steel box).
Using this flash in with the camera shutter set to A mode, once the shutter speed crosses the maximum synch speed, the camera does not fire the flash.
Versus the SF 58
The Leica SF 58, at least used, is about the same price as a fully configured 45CL-4 digital. The SF 58 is very well integrated, supporting fast TTL operation (preflash to flash), exposure comp for TTL, high-speed synch, and automatic zooming to match the focal length of whatever lens is on the camera (assuming 6-bit coding or manual selection). It should be a killer, right?
It’s not as much as you would think. The Metz is deficient in some ways, but it is considerably ahead of the SF 58 in terms of flexibility to use with other cameras, simple controls, putting the flash off the lens axis, and POWER, both in terms of the size of the battery pack and its output. The 45CL-4 is rated for 45m at at 35mm field of view; the SF 58 (like the Metz 58 it is derived from) only hits 58m at the 105mm reflector setting; it’s only GN 35 at 35mm. It is also very difficult to beat the 45 series accessory infrastructure, which includes two of types diffusers (pebbled and opaque white), a telephoto extender, a bounce card, colored reflectors, slave units, and NiMH battery packs.
For social use, indoors, the SF 58 has an edge because it can be taken down and set up quickly. Its balance still is a little awkward, since it seems to be designed for the much larger S series cameras.
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