Kodak DCS Pro SLR/n Digital SLRKodak updates their Pro 14n with a new sensor, improved processing, and greatly reduced image noise.<<Optics :(Previous) | (Next): Shutter Lag & Cycle Time Tests>> Page 6:Exposure & FlashReview First Posted: 02/12/2004 |
Exposure
| Free Photo Lessons | |
|
In any of the camera's exposure modes, except Manual, the exposure compensation adjustment lets you increase or decrease exposure in one-half-step increments from -3 to +3. (For the record, I greatly prefer having the option of a one-third step size on digital cameras, as a full half-stop adjustment is really too coarse, leaving too large a step between one exposure setting and the next.) The SLR/n offers three metering systems: Matrix / 3D Matrix, Center-Weighted, and Spot. In Matrix mode, the camera divides the image area into 10 segments and meters each one individually. The camera then examines overall brightness and the differences between the various segment readings to determine the best overall exposure for the scene. If a Nikkor D-type lens is in use, 3D Matrix metering is available. Also dividing the image into 10 segments, 3D Matrix mode not only reads brightness, but also takes into consideration scene contrast and subject distance to provide a more accurate exposure. Center-Weighted metering reads the exposure from a fairly large area around the center of the frame, while Spot metering looks at only a small point in the very center. If you're uncertain of an exposure, the SLR/n's Auto Exposure Bracketing mode captures a series of images at different exposures, bracketed around the main metered setting. Through the settings menu, you can specify a series of either two or three frames, as well as the order of capture. (For example, under/over/normal vs under/normal/over.) Exposure can vary as much as +/- 2 EV between subsequent shots.
The camera's AE/AF Lock button lets you lock exposure and/or focus without half-pressing the Shutter button. In the settings menu, you can configure the AE/AF button to lock either exposure, focus, or both.
The SLR/n features a Digital Exposure Correction (DEC for short) option through its record menu, a very unusual feature for a professional-level camera. This automatic adjustment examines the image post-exposure, and makes minor adjustments to the tone curve and color balance to produce what it thinks is a more correct overall exposure. Note though, that this doesn't correct for improper shutter speed, aperture, or ISO selections, it merely tinkers with the image data after it's acquired. For JPEG files, the change appears directly in the files themselves. Data in RAW files is not adjusted directly, although an adjustment setting is saved for optional application later, in Canon's Mac- or Windows-based image processing software. This could be a handy option when used in conjunction with the SLR/n's simultaneous dual-format RAW/JPEG file capability. The JPEG files would reflect the camera's adjustments, while the RAW files would preserve the original image data.
I didn't experiment a great deal with the SLR/n's DEC option, after having a somewhat negative experience with it while doing some night shooting at PMA in Las Vegas back when I reviewed the original 14n. Reading about the option, I decided to turn it on, but also have the camera save RAW files as I shot. I figured this would be the best of both worlds, as I'd have the benefit of DEC in the JPEGs, but still be able to revert to the RAW files if I needed to. As it turned out, it was very fortunate that I chose to also save the RAW files, as the DEC pretty much made a hash of the night-scene JPEGs. The problem was that DEC kept thinking that the shadow areas were too dark, tweaking the tone curves to boost the brightness there. Unfortunately, in the process of doing this it horribly amplified the image noise, producing incredibly blotchy shadows. I suspect this feature may work much better under daylight shooting conditions, but once bitten, I've been twice shy, and so haven't revisited it in my work with the SLR/n.
Another option, called "Look" in the settings menu, applies a tone scale/color saturation adjustment to captured images. Four adjustments are now available (up from two when I first tested the 14n): Portrait, Product, Wedding, and Event. The Portrait setting lowers contrast to improve detail in the highlights and shadows, while Product mode increases contrast and color saturation. Wedding seems to boost overall saturation, without overly affecting skin tones, to brighten colors in the image without producing blotchy skin tones. The Event look pumps up the saturation and contrast overall, without any special skin-tone handling. Just as with Digital Exposure Correction, the Look adjustment applies immediately to JPEG files. RAW files are tagged according to the Look they were captured with, and the adjustment is applied when they're viewed with Kodak's Photo Desk software.
Depending on the image file format that's selected, the SLR/n offers an ISO range from 160 to 1600. The maximum for JPEG formats (JPEG only and RAW + JPEG modes) is 800, the range extending to 1600 when only RAW format is selected. While very long shutter times (including bulb exposures) are supported by the camera body itself, sensor noise effectively limits maximum exposure times to a few seconds or less.
New since I first reviewed the 14n is a new "Longer Exposure" mode that enables very long timed exposures, with very low effective ISO values. (This feature was added to the 14n firmware back in September 2003, but this was my first encounter with it.) Longer Exposure mode makes clever use of the SLR/n's processing power to enable long time exposures with very low noise. In this mode, the camera divides the total exposure time selected into a number of shorter exposures, and then averages together the individual images. This is all invisible to the user, the effect is simply that of the camera taking a very long exposure. At the same time, dark frames are captured to subtract-out fixed pattern noise. As an example of this feature, a 2-second exposure in Longer Exposure mode consists of an initial 1/2-second dark frame, four 1/2-second exposures, and a final 1/2-second dark frame. The dark frame results are extrapolated across the total exposure time, subtracted from the captured images, and the resulting frames averaged together to produce the final result. The net of this is that the camera's effective ISO is cut, and image noise is reduced accordingly, thanks to the averaging process.
Because the camera has to capture all the images it needs and hold them in memory to perform the averaging process, only certain combinations of effective ISO and exposure time are possible. Available exposure times range from 2 to 60 seconds, with corresponding ISO values ranging from 50 down to 6. (!)
The SLR/n offers quite a bit of control over noise-reduction processing (particularly in the Photo Desk software), and is overall much more successful at reducing image noise without also losing subject detail than was the 14n. Particularly helpful is the new "Expert" noise-reduction mode in the Photo Desk software, which more aggressively attacks the chrominance components of image noise, without losing too much luminance data. This seems to do a pretty good job at knocking out image noise without losing fine detail, although I still evidence of lost detail in portions of images having subtle contrast. (In my test shots, this phenomena is visible in some areas of Marti's hair in the Outdoor and Indoor Portrait shots, and in the clumps of pine needles in the Far-Field test image.)
White balance options on the SLR/n include Auto, Daylight, Tungsten, Fluorescent, and Flash presets, and a Click Balance (manual) setting. Within each of the presets, you have a handful of options. For example, the Daylight setting offers Standard, Warm, and Cool settings, and the Flash preset offers Standard, Warm, Cool, and Studio options. The Click Balance option analyzes the RGB values from the most recently captured image, or a saved image, and applies them to the next image captured. Thus, you can snap an image of a gray card under specific lighting, and then apply that color balance to each subsequent image. Once you've selected Click Balance, an eyedropper appears over the image, letting you pick the specific area you want to use as your white balance reference.
A particularly nice touch on the SLR/n is the degree of precision with which you can select white- or gray-point references for determining color balance. You can zoom in on the image on the LCD screen and move the selection eyedropper with the arrow keys to sample a specific part of the frame. (See the illustration at right for an example, with an image zoomed way in on the LCD screen.) This is a great feature, making it easy to zoom in on just a part of the subject to select your white/gray reference point. (Other manufacturers should take note of this feature, it greatly expands the usefulness of the manual white balance option.)
The SLR/n also features a Sharpness adjustment, with settings of None, Low, Medium, and High available on the camera. These settings are applied directly to JPEG image files, but once again are simply saved as tags in the RAW-format (DCR) files. Tagged DCR files are automatically processed using the selected sharpening setting whenever JPEG or TIFF files are extracted from them with Kodak's Photo Desk software. The sharpening tool in Photo Desk offers good control, although it lacks an effective on-screen preview of the results of your settings, making it awkward to work with interactively. - See the subsequent software section of this review for more detail on Photo Desk's options and control panels.
A Self-Timer mode provides a 10-second delay once the Shutter button is pressed, giving you time to run around in front of the camera before the exposure.
File Format Issues
I observed in my review of the Pro 14n that the DCR and JPEG file formats were definitely not equal partners in the camera's design and workflow, the in-camera JPEG coming in a distant second for image quality relative to JPEG or TIFF files generated with the Photo Desk software. With the SLR/n, Kodak has made great strides with the in-camera JPEG, to the extent that it now seems eminently usable. For critical work, Photo Desk still gives you much greater control over a variety of parameters, but the SLR/n's in-camera JPEGs are now usable. (Kodak's easy firmware upgrades and regular schedule of updates deserves comment here again. - The improvements seen in the SLR/n in-camera JPEGs are also available to 14n owners, at no cost other than the few minutes required to download and install the latest firmware upgrade.)
Flash
17 meters at ISO 200, translating to a maximum range of 6.1 meters (19.7 feet) at f/2.8 and ISO 200. (By my calculations, this translates to a range of roughly 5.5 meters at f/2.8 and the camera's minimum ISO of 160.)
The SLR/n features a built-in, pop-up flash unit with a guide number of 17 meters (55 feet) at ISO 200. For a standard f/2.8 lens, this would translate into a flash range of roughly 6.1 meters (19.7 feet) at f/2.8 and ISO 200. (Note that the different spec for flash guide number for the SLR/n vs that for the 14n doesn't constitute any increase in power. It's the same flash, it's just that the SLR/n's minimum ISO is 160, so a rating at ISO 100 (as with the 14n) doesn't make sense. A guide number of 17 meters at ISO 200 is the same as a rating of 12 meters at ISO 100.) Depending on the lens in use, the internal flash offers D-TTL metering control in three modes: 3D Multi-Sensor Balanced Fill-Flash for Digital SLR, Multi-Sensor Balanced Fill-Flash for Digital SLR, and Standard TTL Flash for Digital SLR. With 3D Multi-Sensor Balanced Fill-Flash metering (Type G or D CPU lenses), the flash balances the exposure based on readings from the 3D Matrix Metering system. The built-in flash operates in either Front-Curtain Sync, Slow Sync, Rear-Curtain Sync, Red-Eye Reduction, or Red-Eye Reduction with Slow Sync modes. A Flash Exposure Compensation adjustment controls flash intensity, adjusting it from -3 to +1 EV in one-half-step increments.
For connecting more powerful flash units, the SLR/n also features an external flash hot-shoe as well as a PC sync terminal. The same D-TTL flash metering modes are available, depending on the type of lens and speedlight connected to the camera, and the full range of flash sync modes are available as well.
The hot shoe on top of the SLR/n accepts standard Nikon speedlights, and the camera offers full D-TTL autoexposure capability with the SB-80DX, SB-28DX, and SB-800 AF models. (The SB-50DX also supports full D-TTL exposure, but not some of the other modes such as Auto Aperture or Non-TTL Auto that the others do.)
Continuous Shooting
Through the camera's Drive setting, the SLR/n features a Continuous Shooting mode that captures a series of images for as long as the Shutter button is held down. The manual claimed a frame rate of 1.7 frames/second, but brief tests of my own showed a maximum rate of closer to 1.6 fps. (I'll update my measurements of the camera's timing after I return from the PMA show and have a little more time to spend with it.) Actual frame rates will vary, depending on the JPEG compression and image resolution settings, and the number of images in the series will depend on the amount of available memory space. The SLR/n does appear to have a larger buffer memory than the 14n did though, as it can capture up to 18 full-resolution frames in rapid succession in RAW mode, and up to 16 frames of maximum-resolution JPEGs.
Sound
The SLR/n also lets you record short clips of sound to accompany captured images. The manual doesn't specify how long you can record sound, but I can confirm that the limit is something greater than a minute, as I successfully recorded for at least that long.
Variable Cropping Ratios
An unusual feature of the SLR/n is it's provision for a variety of different cropping aspect ratios. "Aspect ratio" is simply the ratio between the length and width of the image. Common examples are the 2x3 ratio of conventional 35mm film (making 4x6 prints a perfect fit), the 4x3 ratio of computer screens and most consumer digicams, etc. The Pro SLR/n offers aspect ratios of 2x3, 4x5, and 2x2. Like many other exposure parameters, the crop aspect ratio setting applies directly to JPEG images created in the camera, but only exists as a "tag" on RAW-format DCR files. With DCR files, the full sensor information is saved in the file, regardless of the crop ratio selected, but the chosen crop ratio is recorded in the file header. The crop is applied when the images are opened in the Photo Desk application, and the crop can also be changed at that point as well.
Follow Imaging Resource: