A Photographer's Advice on Fragmentation Photography

 

By: Mark Wagner



When it comes to fragmentation analysis technologies, image quality is paramount to ensure accurate results when displaying size distributions. WipWare differentiates itself by having in-house photography experts to ensure you can take your fragmentation data to the bank. Read past the jump for the first in a series of articles featuring expert advice from in-house photographer Paul Chivers on how you can optimize your images.

Something we hear on a regular basis is "Okay...image quality is important, so let's go out and get the highest megapixel camera available so we can analyze the heck out of this material"... Well, hold your horses, Ansel Adams - although important in some applications, higher megapixel images may actually reduce the analysis quality when working with fragmentation technologies. Think for a minute about an image you would take that would require a high megapixel camera; perhaps an image you want to enlarge and want to hang in your office?... Well, aside from WipWare President Tom Palangio, (he's seriously obsessed with fragmentation) chances are you aren't about to display your 'fave frag' images anywhere any time soon. I know my wife would kill me if I tried.

I digress. In a world so focused on megapixel count, users tend to lose sight of the use of camera technologies as they relate to mining, aggregates and fragmentation analysis as a whole.

Here to help debunk some of the imaging myths when completing particle size analyses is Paul Chivers, WipWare's media and public relations specialist. Paul knows his way around cameras having spent almost 30 years as a photojournalist and also taught college-level continuing-education photography courses for more than 25 years.

Q: Aren't more megapixels better?

A: They are if you're making large fine-art prints that look best from high-resolution files, but if your needs are more modest those extra pixels can actually work against you.

There are 36MP and even 50MP cameras out there now and popular thinking goes that more is better, but that's only correct to a point. Let's say you have a more modest 18MP camera. It produces files that are 5184 pixels on the long dimension. You can distribute those pixels at 300 per inch to give you excellent print quality at 17.3 inches, but that same file will display at more than 50 inches on a computer monitor! There are very few monitors that can display images greater than 2000 pixels at full resolution. This file will consume 25Mb of storage space in Raw format or 7Mb in JPEG format on your memory card or hard drive.

As a complete aside, it may be worth noting that sensors in the most advanced digital cameras are now out-resolving lenses. What's known as the 'diffraction-limited aperture' has been creeping upwards as pixel counts increase to the point where images taken with apertures smaller than f5.6 to f8 exhibit visible loss of sharpness. You can read more about this condition here. The same condition existed with film, but didn't usually become evident until well below f11. That's one reason why we see lenses redesigned and re-released as 'II' and even 'III' versions as is the case with many Canon lenses.
Analyzing large files can consume considerable computer resources and is rarely required for effective fragmentation analysis. For example, even if your sample width is quite large, six meters (20 feet) or so, a five megapixel camera can still resolve particles as small as 7.5mm (1/3 inch).

WipFrag contains a feature that automatically downsizes large files to approximately 1600 pixels for analysis. This is on/off by default. Auto-Resize will reduce the size of a JPEG file from 7 or 8Mb to approximately 350kb, which for most purposes will be perfectly adequate for fragmentation analysis. It will transfer via email/FTP in a fraction of the time the full-size image would take, and will consume much less storage space.

With this in mind don't get hung up on megapixels when choosing a camera for fragmentation analysis, where image quality trumps image size every time. Instead, consider the shooting/lighting conditions. If you're working underground, you need a D-SLR, and it should be well-rated for high ISO images. The larger sensors in D-SLR-s yield much cleaner low-light images with better shadow detail than compact cameras are capable of. There's a good series of comparison photos illustrating this here. Compact cameras with good quality optics can often be used for outdoor sampling in good lighting conditions but beware high megapixel compacts with low-quality lenses.
Check back for the next installment in this series!