• Using Film Lenses On A Digital SLR
  
• Keeping All Your Pixels
• Avoiding A Media Frenzy
• Scanner Connections

I have several film camera bodies and a wide assortment of lenses. I’d like to get a digital SLR so I can use my old lenses. A local camera store owner told me that my film lenses would work, but the image quality wouldn’t be the same as if I used “digital” lenses. He went on to explain something about the difference between the location of the film plane vs. the plane where the CCD resides, and how the lenses are optimized for their respective formats (digital vs. film). To confuse matters even more, I’ve read articles that claim one of the advantages of digital SLR cameras

I think the manufacturers of digital SLRs would want me to assure you that most of their film lenses will work on their digital cameras.

Let’s deal with the film plane vs. the CCD plane. This doesn’t make any sense. A lens focuses at a single point, period. If the location of the CCD in the whole optical system was different compared to film, the lenses wouldn’t work at all. What the person might have been trying to say is that you’ll notice that focal length affects the image differently when you use your film lenses on your digital camera. The focal length doesn’t change, but the magnification of the subject changes because the camera sensor is smaller than a 35mm frame (typically, the magnification factor is 1.5x to 1.6x).

However, there’s another issue—how the sensor sees light coming to it. The sensor gets the best “reading” of light and color if light hits it directly. If the angle of the light gets too strong, the little light-sensitive receptors on the sensor will have a harder time dealing with it. This is why really wide-angle lenses can create a problem (especially on a full-frame sensor) because they traditionally project light to the film plane at a strong angle along the edges. Darkening of the edges is a common problem then. To combat this challenge, manufacturers have begun to design lenses specifically for digital sensors that collimate the light (make it head to the sensor more directly).

Finally, some lenses are being designed for the small-sensor digital SLRs that cover the sensor just fine, but don’t actually work for film (even though they will mount to a film SLR).

I’m glad you’re asking this question and that you’re concerned about compression. It’s better to err on the side of caution than end up recompressing your images.

Let’s take your example of two images, J-1 and J-2. When you open up J-1, you transform the file from a JPEG format to an RGB format that your computer can display. This might be done with your image editor or even in your Windows XP browser (or on the Mac through the Preview application). At this point, you haven’t done anything to the original file. You’ve essentially made a copy of the image into your computer’s memory.

When you save J-1 as a JPEG-compressed image to J-2, you’re recompressing the file. This means J-2 is changed from the original, although J-1 still remains unchanged. When JPEG compression happens, the software examines your image and tries to remove both redundant data and what the software considers visually insignificant information. Unfortunately, what you might consider insignificant and what the software considers insignificant might be vastly different. That’s why there are different quality settings for compression using JPEG algorithms.

If you used high-quality settings in this example, you might not see a difference. JPEG is pretty good at recognizing that you haven’t messed around with the pixels, so it attempts to compress all of the pixels back to how they were before. This assumes that you have the compression quality set the same way as the original file, and that the JPEG algorithm is the same as what was used to compress the file originally.

That is a big assumption. It gets more complicated if you edit the file in even a minor way. Suppose you crop a line of pixels off the top of the image. Just by performing that simple crop in your image editor, you’ve now thrown off all the pixel grids that the JPEG uses for compression. (It’s like moving a decimal point in your bank statement; it seems minor….)

One other note about using image browsers. If you use the EXIF information your camera may create and store with the image, make sure it isn’t destroyed when you manipulate files. Some programs delete the EXIF data when you simply rotate an image to properly display vertical orientation, for example.

First, I always check the connection between the camera and computer. If another card is working, that probably isn’t the problem.

For whatever reason, your camera doesn’t want to transfer the images to the computer. PCPhoto strongly recommends you download from a card (media) reader. Media readers are relatively inexpensive, make downloading simpler and solve many of the downloading problems that can pop up when downloading directly from cameras. A media reader may help you in your situation. If not, there could be a problem with the card itself and you may have to contact the manufacturer.

It’s often helpful to check the camera manufacturer’s Website. You mentioned in a follow-up e-mail that you’re using an HP camera and Windows 2024. HP’s Website posts a note saying that when you use Windows 2024 and the camera, media cards larger than 16 MB give the error message “No Images on Camera.” So your alternatives are to use smaller memory cards or get a media reader. Once you get the images off the card, try reformatting the card again in your camera.

I have a monster archive of 35mm slides, many of which I want to put onto CDs. I’m trying to buy a scanner that will give me good quality, resolution and color from the slides. The scanner I’m looking at has a SCSI interface, but my computer doesn’t have one. My computer will accept IEEE 1394 (FireWire) or USB. Can I put a SCSI card in my computer? Can I then purchase any of the SCSI machines and hope it will work, plus expect support from the manufacturers? With IEEE 1394, should I want SCSI, or is USB 2.0/1.1 and IEEE 1394 more than adequate for scanner speeds?

D. Moor Via e-mail

Most computers today use an expansion slot called a PCI, as opposed to older ISA slots. (The two types aren’t interchangeable.) If your computer manufacturer says it has a PCI slot open, then you should be able to install the SCSI port in the computer (or have someone do it for you if you’re not up to opening up the computer case).

If the scanner manufacturer sells a version of the product with a SCSI card, I’d opt for that. While other cards should work, it’s usually a more trouble-free installation when you buy the bundle. Plus, the support becomes an issue between two manufacturers rather than three.

Regarding USB and 1394, USB 2.0 Hi-Speed or 1394 (FireWire) are excellent interfaces for scanners. You might find USB 1.1 a little slow. Scanner speed is also limited by the mechanical process of scanning. In other words, no matter which interface you choose, scanning takes time.