Memo to Nikon users: Get out your checkbooks, up the credit limit on your Visa cards or tap the home equity line of credit. On Dec. 19, Nikon ships the new king of the hill in the digital single-lens-reflex megapixel wars.

The Nikon D3x is a 24.3 megapixel monster with a monster price tag: $7,999.99.

But that’s the same street price that Canon has normally charged with its megapixel king: The 21.9 megapixel EOS-1Ds Mark III.

Since I shoot with Canon and mortgaged my soul earlier for the 1Ds MKIII, I don’t have to rush out and buy the new Nikon but you can bet a lot of people will.

Which begs the question: How many megapixels are enough? At what point does the detail delivered by the megapixel giants become more than the eye can see?

My previous high-megapixel top dog in the camera bag was a Canon EOS-1Ds Mark II which — at 16.7 megapixels — delivered tack sharp enlargements up to poster size: 36 by 24 inches. I shoot high school sports and other photojournalism assignments with a Canon 1D Mark III: A high-speed 10 megapixel camera that delivers more than enough detail for newspaper resolution.

I started shooting digital for journalism work in 1999 when Nikon released the 2.7 megapixel D1.  I shot dozens of assignments until replacing it with a 4.1 megapixel D2H in 2003. Problems with the D2H led me to change from Nikons (which I had used since 1965) to Canon in 2004 when I bought the 8 megapixel 1D Mark II and 16.7 megapixel 1Ds.

Canon replaced the Mark IIs with the 10 megapixel 1D and 21.9 megapixel 1Ds late last year but some shooters reported problems with the autofocus on the 1D and a number of shooters switched back to Nikon because the new D3 offered 12 megapixels, a better autofocusing system and incredibly high ISO capability (up to 25000).  Canon upped the ante recently with the $2,700 5D MKII which offers 21.9 megapixels, the same high ISO range as the D3 and high-definition video.

The digital age means a shorter lifespan for camera bodies. In the film days, a professional SLR body from Canon or Nikon had a market life cycle of 10 years. The digital bodies have a shelf life of about two-and-a-half years.

I’ll stick with Canon. I have a tidy sum invested in camera bodies and lenses and haven’t had any of the autofocus issues with either of my MK IIIs. But then I’m old-school and focus most of my shots manually anyway.

The cost of professional photo equipment has reached the point that when I drive to cover a sports event at Floyd County High School, I’m hauling camera equipment that cost more than twice the sticker price on my Jeep Wrangler.