it has a 12 megapixel camera thats just as good as the one on the iphone 6s Steve Kovach/Tech Insider

Apple announced the iPhone SE on Monday, and it looks great. Apple's marketing it as a device sized for fans of past, smaller iPhones but wielding all the oomph of the 6s's internal machinery.

But if Apple's own spec sheets can be believed, that's not entirely true.

Reports on the phone's camera have largely focused on its rear 12.1 megapixel sensor, which appears identical to the the one in the 6s. But, as we've written before, the most important factor in a camera's quality isn't its sensor, but its lens.

And the SE's forward-facing selfie lens appears to be substantially lower quality. An Apple spec sheet lists every other selfie camera on a current apple device as having an f/2.2 aperture, while the SE has an f/2.4. (In aperture measurements, lower numbers are better.)

Here's why that small-seeming difference actually matters a great deal.

Screen Shot 2016 03 21 at 6.09.31 PM Apple

Aperture is a measure of how wide a hole the lens opens to allow light through onto its sensor. And the difference between an f/2.2 lens and an f/2.4 lens is substantial enough to make a difference in photos.

Here's the math-y bit:

An f/1.4 lens is twice as bright as an f/2 lens, which is twice as bright as an f/2.8 lens, which is twice as bright as an f/4 lens and so on. (Sharp-eyed readers will see that those gaps don't mark a straight line. Optics are complicated.)

The difference between f/2.2 and f/2.4 marks a significant chunk of the way between f/2 and f/2.8. While I don't know enough optical physics to tell you precisely how big a difference it will make (it's in the vicinity of 25%), I can tell you from my experience with DSLR lenses that it will be noticeable in your images.

Math-y bit over.

What this means for users is that selfies and other front-facing camera pictures on the iPhone SE should be somewhat darker and grainier than those on the 6s, barring some as-yet unmentioned improvement in sensor technology.

Also, that attractive effect where the background is softly out of focus when the subject is close to the camera will be weakened, for reasons explained in this post.

Now, the front-facing camera may be the neglected stepchild of the iPhone engineering family. (It's only got 1.2 megapixels. And even as someone who rails against focusing on megapixels, I have to say that's junky.) But even this relatively minor concession on aperture is a bit surprising.

Apple loves to tout its phones' skills as pocket shooters, but Android devices like the Galaxy S7 are already blowing iPhone apertures, and quality, out of the water. And companies like LG are working on some interesting, though so far unsuccessful, design innovations that Apple can't match.

Maybe it was a necessary concession for the smaller device to achieve its lower cost, but it's significant enough regression to make us sit up and notice. Here's hoping the iPhone 7 ships with some competitive lenses again.

EXCLUSIVE FREE REPORT:
25 Big Tech Predictions by BI Intelligence.
Get the Report Now »