Q1: So, Apple chose a five-element lens, a larger apperture and a backside-illuminated sensor and you say these are good choices. Does that mean that they made all the right choices for their camera? Or could they have compromised somewhere else in the camera?
A: For a camera phone, I think they made pretty good choices. I have seen photo shots comparing all the previous iPhones and the last one is clearly their best camera phone so far.
Q2: I noticed that many camera phones have quite a lag, much more than standalone cameras. Why does it take so long to shoot and process a picture?
A: Most of the time it's due to the focus. It has to find the subject, and since they work by contrast detection, it is a bit slower than phase detection used in digital single lens reflex (DSLR) cameras. Contrast detection is slower and since the size of the sensor itself is very tiny, it doesn't see the light as easily as the bigger sensors in digital imaging cameras. That, plus the fact that most lenses in camera phones are not that bright -- most are not 2.4 -- contributes to the slow focus.
Q3: So, does that mean that, by looking at the lens, if it's visibly smaller than on other camera phones, it might be a good indication that it might perform better in low-light conditions (if there's no backside illumination)?
A: Trying to evaluate lens size could be misleading. You should read the aperture specification instead.
Q4: So there's less light so it's harder for the focus processor to do its work?
A: Yes. But there are many possible causes: the processor might
Expert Quote
"Is the processor ready for photography? Is there enough light? Does the lens let enough light in? Many factors can make auto-focus slower."
not be optimized for photography, then the lens itself might not let as much light in, and the sensor might also be smaller. All of this makes auto-focus slower on a camera phone.
Q5: Well then, why don't they just put gigantic lenses to grab all the natural light and part with these stupid LED flashes?
A: These lenses would not fit in a phone and would probably bump up the price.
Q6: Earlier, you said that face detection helps focus faster. Many camera phones now have face detection. Does that mean they'll necessarily have less of a lag?
A: That's not exactly what I meant. Face detection helps to avoid focusing on the wrong subject.
Q7: Speaking of face detection, what happens, then, when there's no face in a picture?
A: Most of the time, it focuses on the nearest subject.
Q8: What's the deal with Xenon LED flashes? Are they special LED flashes - are they more powerful or easier on the batteries?
A: Flashes on camera phones are not real flashes per se, in fact they are lights. A real flash is a strobe light that pops for a fraction of a second and they are not used on camera phones. They use LED lights, and they use them because they are very efficient -- according to me they are the most efficient lights available on the market. They don't drain the battery too much and they are quite bright for their size.
Q9: Do you have any idea why there are no regular flashes on camera phones?
A: To use a standard flash, they would have to install a condenser and the strobe itself. All the parts that make up the flash are larger than a small LED, which would make a phone too big for consumer use.
Q10: However, camera phone "flashes" generally don't really make a big difference in dark situations. Are sensor technologies going to evolve to the point where we can take good pictures without LED lights or with very weak lights?
A: Since camera phones use LED lights that are weaker than actual flashes, they will only be effective in short distances. To make them more useful in longer distances with the same amount of light, we need to improve sensors even more.
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