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General Digital Camera Tips and FAQs

Index of Topics:

JPEG vs TIFF vs RAW Comparison
White Balance and Exposure when shooting JPEG
Shooting in Mixed Lighting - Using Colour Gels
Memory Cards - Care and Feeding
What DPI is my Camera... or... How Big a Print Can I Make?

This page is meant to provide a point-form overview with answers to some common digital camera questions. It is obviously not designed to be a comprehensive guide by any stretch, however if you have a specific topic request, email me and I may consider adding it in the future...

 

  • JPEG vs TIFF vs RAW Comparison
    • JPEG Advantages
      • Small file sizes - fit more images on memory card and on backup CDs.
      • Faster Shooting - shorter card write time and usually more buffered images.
      • Depending on the camera, image sharpness and contrast may be sufficient for smaller print sizes (8x10 or less) without additional post-processing.
    • JPEG Disadvanges
      • Requires accurate exposure and white balance setting at time of shooting. Assume your exposure latitude to be roughly equivalent to slide film in most cases.
      • May introduce image "artifacts" such as colour noise or splotchiness in shadows or large areas of solid colour.
      • Image artifacts could limit your ability to upsize or upsample files for larger prints. In some cases, using Genuine Fractals to upsize JPEG images can be beneficial since it may reduce image artifacts when compared to other techniques.
    • TIFF Advantages
      • No compression is used, thereby minimizing artifacts.
      • Images can be archived straight from the memory card with no conversion necessary for clients who demand uncompressed files.
    • TIFF Disadvantages
      • Huge file sizes are generally too much for most camera's internal processors to handle with any kind of speed.
      • Long read and write times from memory cards and minimal shot buffering makes for slower shooting.
      • Large file sizes, typically 5-10 times the size of a fine JPEG means fewer images can be stored on your memory card.
      • Generally shooting TIFF files still requires accurate exposure and white balance settings at time of shooting. Exposure latitude is still roughly equivalent to slide film in most cases.
    • RAW Advantages
      • No compression is used, thereby minimizing artifacts.
      • No in-camera processing such as sharpening or noise reduction is used thereby allowing interactive adjustments during image post-processing. This would allow for optimal image up-sizing if required at a later date.
      • Full dynamic range of camera's sensor is available for post-processing to adjust exposure, contrast, white balance, sharpness, colour space etc. Exposure latitude is much wider and, depending on the camera, begins to approach what one would expect from negative film.
      • Reasonably small file sizes that are 1/3 to 1/2 the size of a TIFF file.
    • RAW Disadvantages
      • Still significantly larger than JPEG file sizes allowing for fewer images stored on memory cards.
      • Usually will be processed somewhat slower than JPEGs in camera - but this depends on the camera also. Also may reduce your shooting buffer size.
      • Depending on your computer and what software you are using, you could see significantly longer processing times for opening and converting images to other formats such as TIFF or JPEG and the subsequent post-processing of the images.
      • Generally, you will not want to supply clients with RAW files as most programs won't be able to open them. There are exceptions to this rule however... when in doubt, ask your client what they prefer!
  • White Balance and exposure when shooting JPEG or TIFF files
    • Since you have limited adjustment capabilities when opening a JPEG (as noted above) it is important that you dial-in your white balance as accurately as possible and ensure that your exposure is accurate.
    • Of course, you can make exposure and colour-balance corrections to JPEG images after-the-fact however, dramatic adjustments could introduce posterization and destroy the smooth tonality of your images. Generally speaking, small adjustments and tweaks will not visibly harm your images.
    • These next two points are somewhat at odds with my last one, but realistically you will often need to tweak images slightly, even when shooting JPEGs, therefore...
      • Depending on the situation, you may also want to set your camera (if it can be) to a low contrast setting in order to maximize your exposure latitude. Shooting in low contrast will usually give you a little more room in both the highlight and shadow ends of the image, allowing you to more easily make some adjustments for white balance or exposure after the fact. Note that shooting RAW images will still give you by far the greatest latitude for exposure corrections.
      • Avoid using auto-white-balance whenever possible! If you use auto-white-balance you might find each and every image to have a slightly different colour balance depending on how the camera's white-balance algorithm perceives the scene you're shooting. This would make it impossible to create an action in Photoshop, for example, that will batch-process and correct the colour on a series of images. It would be better to used a fixed white balance setting that is as close as possible, even it is not perfect, rather than using auto-white-balance and then have the colour on every image looking slightly different. That having been said, some modern cameras provide fairly accurate auto-white-balance and sometimes have external white-balance sensors to assist in determining the correct setting.
  • Shooting in Mixed Lighting - Using Gels with your flash
    • Since digital cameras are, in general, very sensitive to the colour temperature of lights, you may find it advantageous in slow shutter-speed / fill-flash situations, to gel your flash so that it more closely matches the colour of the predominant ambient light in your scene.
    • As an example, if you are shooting in such a situation where there are bright overhead fluorescent lights and you have set your camera's white balance for flash, you may find that your subject will have a green cast on the tops of their head and shoulders where the fluorescent lights are reflected more strongly. What can you do to minimize this?
      • Depending on your camera, you could try and set your white balance setting somewhere in between strobe and fluorescent and this may improve the colour balance somewhat. However, a better way might be to set your camera's white balance to fluorescent and then put a green gel over your flash. This will minimize the colour temperature differences between your flash and the ambient light and yield a more natural looking image.
      • You could carry a small selection of green, amber and blue gels with you and then experiment as the shot requires in order to get the best match between your flash and ambient light.
  • Memory Cards - Care and Feeding
    • Temporary memory card corruption seems to be a fact of life (so far) if one is not careful when shooting with digital cameras. What can you do to minimize its likelihood and what can you do when it occurs?
      • Don't keep on shooting when your camera's batteries are getting low.
        • Carry lots of spare rechargeable batteries and swap a fresh one in before you run out of power. If the camera is trying to write an image to a memory card when its batteries are nearly exhausted, it may not reliably complete the write. At this point it is possible that the memory card's low-level directory structure might become damaged and you may not be able to open the last image that was written or, even worse, you may put in a new battery but all subsequent images saved to that card may become corrupted, even though the camera seems to be working fine.
      • Never open, rename, delete or move files around on your memory card while you are accessing the card with your computer.
        • This seems to be a common source of memory card corruption, so always, always, always (!) copy your files from the memory card to your computer's hard drive before manipulating or editing them in any way.
      • Always format the card in the camera after downloading and verifying your images.
        • If your card has a even a slightly corrupted low-level directory structure (where you haven't necessarily come across any problems), simply deleting all the images (as opposed to formatting the card) will not repair the card's directory structure. Continued use of the card may cause more serious image corruption down the road.
        • However, on some cameras, even formatting the card does not guarantee that the directory structure gets rewritten.
        • If you have any reason to suspect problems with a memory card, it is a good idea to use a program such as Lexar's Image Rescue (which only works on USB enabled Lexar CF cards) or the free program CardWiper, which will work on any memory card, and is available from www.datarescue.com. These programs both allow you to "zero" a memory card which will then force the camera to reformat and recreate the card's directory structure.
      • What do you do if you have a corrupted card and are unable to open the images?
        • Use card recovery software such as Lexar's Image Rescue or the excellent Photorescue from www.datarescue.com. Again, the Lexar software only works with USB enabled Lexar CF cards but Photorescue will work with any memory card.
          • Both these programs will attempt to recover images from corrupt, erased and even formatted memory cards (but not a "zeroed" or "wiped" card). Photorescue seems to be the more robust recovery program and will often even recover images from memory cards that are actually damaged and failing. Lexar's software requires that the card still be functioning properly however with Image Rescue, you can also perform card diagnostics and reformat cards to factory specifications. Photorescue is strictly an image recovery program.
          • I consider both Image Rescue (if you are using Lexar Cards) and Photorescue to be "must-have" programs for any serious digital photographer.
  • What DPI is my Camera... or... How Big a Print Can I Make?
    • Your camera does not really have a "dpi" in the important sense of the word. Your camera has horizontal and vertical pixel dimensions, for example, 1600x1200 pixels, 2572x1704 or 3000x2000 pixels etc. If you divide one of these pixel dimensions by your desired printing size, you can then calculate what dpi an image your camera will give you. Examples follow...
      • 1) Your camera has 1600x1200 pixels, and you want to make a print that is 10 inches wide... so 1600 (the long dimension) divided by 10 equals 160, or 160 dpi. So, if you do the math, your 1600x1200 camera can give you a 7.5x10 inch print at 160 dpi.
      • 2) Your camera has 3000x2000 pixels, and you want to make a print that is 14 inches wide... so 3000 divided by 14 equals 214 (rounded off), or 214 dpi. So your 3000x2000 camera can give you a 9.3x14 inch print at 214 dpi.
    • So really... how big a print can I make? Don't I need at least 300 dpi for a good print?
      • If you don't interpolate, or resize, your image, then the larger you print, the lower the effective dpi will drop. I find that for high-quality printing, around 180 dpi is about as low as I would want to go.
      • If you are trying to push a relatively low resolution digital camera file too big and the dpi drops too low, you will start to see "pixelization" or a lack of smoothness in the image. The image will start to look "digital", so...
        • You can either upsample or resize and image in a program like Photoshop to increase the effective file size (thereby increasing its dpi at a given print size), or you can use a third party program or plugin like Genuine Fractals to do the resizing. If you size up an image in Photoshop and the result is a little rough looking or is really lacking sharpness, you may want to try out Genuine Fractals. I find it sometimes does a better job than Photoshop when upsizing "rougher" looking images.
        • The practical limit of how large you can go is very dependant on the quality of the original digital file - you will have to experiment and see. For example, a $4500, 4 million pixel, professional digital SLR is generally going to look a heck of a lot better upsampled and printed to 20x30 inches than an $800, 4 million pixel digital point-and-shoot camera.
    • Lastly, don't confuse the image's dpi (as discussed above) with a printer's rated dpi. These days you can find inkjet printers rated at 1440dpi, 2880dpi or even 4800dpi. This is the dpi at which the printer lays down its microscopic ink droplets on paper, not the resolution of image that it requires in order to make a good looking print. Even if the printer is a 4800dpi printer, it will still make a great looking photographic print with an image that is only 200 dpi. If you don't believe me, just try it...

Mike Mander
Beau Photo Supplies
May 2003

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