Not that it makes as much a difference as you may reckon, but the D90 Digital SLR has a minuscule (12.
3MP) image sensor than the less costly EOS Rebel T1i EF (15.
1MP).
If those specifications were all the information you had, then it would appear reasonably open-and-shut that the Rebel T1i SLR, is the nicest Single Lens Reflex camera for the money today.
Unfortunately for SLR camera buyers, that's not necessarily the case.
There were some better image sensors (Canon 40D) that could have been used when designing the T1i.
I'm certain you've learned in some of my other articles, that cramming more megapixels doesn't instantly create great images.
The image sensor has to be large enough to handle the extra megapixels.
To achieve a higher megapixel rate, Canon made a design decision to place the pixels closer together, and to use somewhat smaller pixels than the D90 Digital SLR uses.
It's most commonly used way to get more pixels into a smaller sensor.
This contributes to a specification known as pixel density.
When it comes to the T1i, it is about 50% higher than the D90 Digital SLR.
That is 4.
5 for the EOS Rebel T1i EF, and 3.
3 for the D90 Digital SLR.
Having a higher pixel density can end up causing several problems.
When researching for lenses for your SLR camera, megapixels is another thing that plays into that purchase.
The better lens with high resolving capacities that are fashioned to work with more megapixels, aren't usually the less expensive lenses.
Canon has decided to parcel the EF-S f/3.
5-5.
6 18-55mm IS with the Rebel SLR T1i, and it wouldn't be my lens of choice for a digital SLR that supports 15.
1 megapixels.
In this writers humble belief, a better zoom lens for the T1i SLR would have been the far advanced 18-200mm Canon EF-S.
Other important SLR camera features, like diffraction, dynamic range, and ISO can be affected adversely by higher pixel density.
The closer you look at the higher megapixels of the T1i, the less of a compelling argument, it has over the Nikon D90.
An digital camera industry bench mark used to evaluate RAW sensor information is the Dx-O-Mark test.
Testing between the EOS 50D (same image sensor used by the T1i) versus the Nikon D90 DX, show the Nikon D90 12.
3MP to be much more capable.
There's every reason to believe that emerging EOS Rebel T1i EF test results will line up to the EOS 50D data.