Enlarging Analog versus Digital


Today’s Question: You wrote: “Whenever you enlarge a photo you are degrading image quality to some extent.” I think this was also true in my film days, which is why I bought a “Portrait Lens.” Could you comment and compare film and digital?

Tim’s Quick Answer: There is indeed a degree of image degradation when enlarging either an analog (film) or digital image. However, film did have bit of an advantage in this context by virtue of being a format that was analog in nature, without having discrete pixel values as is the case with a digital image.

More Detail: It’s a bit of an oversimplification, but you can think of the process of enlarging an analog image as projecting the image at a larger size. For example, if you project a film slide with a projector, you can create a larger image by simply moving the projector farther from the screen you’re projecting onto.

Of course, there is still some degradation, such as the image appearing less sharp the more you enlarged it. But the fidelity of the image would be retained very well due to the analog nature of the original.

While digital capture provides a variety of advantages, it does introduce some challenges when it comes to enlarging the image. Rather than simply projecting the image onto a larger screen you effectively need to add pixels to the image. This is done by calculating the color values for new pixels based on the color values of surrounding pixels. You’re basically spreading the existing pixels out and then adding new pixels in between. This causes a loss of sharpness and a degree of lost color fidelity.

It is important to note that today’s digital cameras have exceeded the capabilities of most film cameras in terms of resolution and color fidelity. Even with the theoretical advantages of film in terms of enlargement, I would say that today’s digital cameras produce images that can be enlarged with greater quality that what was possible with film due to the inherent limitations involved and the improvements in technology with digital.

It is difficult to compare older technology with newer technology, but in general terms it is fair to say that there are differences in how enlargements were degraded between film and digital captures. There are similarities and differences with both, and of course differences depending on the level of technology for the different capture formats being compared.