"We call them smartphones, but the phone is the least important part. I would love to be the one who comes up with a new name for these," says Dan Rubin, arranging the four sleek somethings delicately on the table, weighing each in his palm. "I take smartphone cameras very seriously, and I have done ever since the iPhone 4 came out, which was the first phone camera that was good enough for practical use."

That was in June 2010, and Rubin traces the worldwide surge in mobile photography to that release, combined with the launch, four months later, of Instagram. "That was serendipity on a massive scale. That combination is what got me shooting every day – it's what made me a professional photographer."

Rubin is a renaissance man for the digital age, working in software and product design, and pioneering a serious, professional approach to smartphone photography, which he considers no less rewarding than taking pictures on his Canon 5D Mk II. "These are the most used cameras in the world now, and because those photos are all being shared, we are seeing more of the world than ever before, which I think is fantastic. You can do a whole lot with a camera phone; under the right conditions with the right light, the right framing, the right focus, you wouldn't necessarily be able to tell a photo wasn't shot on a big camera."

Smartphones have already rendered point-and-shoot cameras almost obsolete, and Rubin thinks they are now even threatening the DSLR. "Software intelligence is where they can potentially be ahead of Canon and Nikon, and already are in some respects. People look down on mobile photography, or say it's lazy, but camera phones encourage us to take more photographs, and I think the more we take photographs, the better photographers we'll be." The theory certainly works for Rubin, whose half-million-odd Instagram followers are constantly shocked that his photos are taken on phones. "It doesn't matter what hardware you have," he says, "the important thing is learning how to see."

8 megapixels, dual warm/cool flashes, iOS 7.0.3, from £549

iPhone5s, gold.

"I've owned every single model of iPhone except the 3GS, so I'm very familiar with the software and the device history. That said, I don't buy Apple products simply because I pray at the church of Steve Jobs, I'm happy to use alternative products if they're good.

"The best way to discuss this model is to compare it to previous iPhones, and the 5S's faster processor improves both the camera and the post-processing. The 5S uses a much-improved flash that measures the white-balance of the image in a fraction of a second before taking the picture. The flash then varies the intensity and combination of the two flashbulbs, which are different-coloured, to balance the colour of the image. It's a very effective idea, which I've never seen on any other camera.

"The burst mode, which takes 10 frames per second, is amazing, When I was taking street photography in India, it allowed me to capture things I could never have got any other way. It blew me away, and it reminded me of Arthur C Clarke's quotation: 'Any sufficiently advanced technology is indistinguishable from magic.'"

20.7 megapixels, 5" display, Android 4.2, £599

Sony Xperia z1.

"The Sony is the biggest physically and in terms of screen-size it's almost overwhelming, and the benefit for that size isn't apparent. It's borderline uncomfortable, and even after a week I'm not used to it, while with the Nokia I never felt that way. It also feels very clean and clinical — cold even. I was terrified whenever I held it that it was going to slip out of my hand.

"Having more screen real estate is good for looking at photos, but for taking photos there is a threshold, and I think the Sony has crossed it. At one point you have to say, 'I don't need a TV in my pocket.' The size of the screen and the number of megapixels are the phone's USPs, but the size ends up being more of a hindrance and the megapixel is a red herring – more megapixels don't necessarily mean a sharper image. Of all of them, the Sony is the only one that feels like it doesn't have any one standout feature which makes it take better pictures."

41 megapixels, optical image stabilisation, Windows Phone 8, from £549.99

Nokia Lumia 1020.

"In terms of usability, it's a tie between the Nokia and the iPhone, but of all the phones the Nokia is the only one I don't want to give back – I have an emotional attachment to it. Nokia has always been known for making good hardware and that hasn't changed – it feels exceptionally well-made and the reason I loved it is that it feels like it's been lovingly built.

"It's the only phone of the four that has a slightly more colour-saturated default setting: a barely perceptible difference but a bonus for people who just want to take good snapshots. More interestingly, there is a hardware gyroscope inside the phone to perform image stabilisation, which is very impressive. It means you don't need a steady hand or a faster shutter speed because it's doing physical adjustments. As a software designer I'd say that the camera app on the Nokia is very elegantly designed – the others are garish, while this is very clean. Windows phone as a platform falls down a bit, however, because there aren't many apps available yet: you can't have either Snapseed or Instagram, and I hope that changes because I like this device. It wouldn't stop me from owning one though. As an iPhone owner I would still buy a Nokia, and that says a huge amount to me."

16 megapixels, external lens, Android 4.2, £449.95

Samsung Galaxy S4.

"The size of the lens contributes slightly better quality in certain situations. It's still a very small lens, but if you do want a camera more than a phone, then the Samsung has an edge — the physics are a just bit better. The standout feature of the big lens is the device's hardware zoom, which goes up to 10x.

"The zoom is brilliantly sharp and clear, and the software zooms on the other phones don't come close. The downside of it is that it's uncomfortable to hold. The exterior lens feels like it's in the way, and every time I pick it up I feel worried that I'm smudging or scratching the lens.

"Size is the trade-off. If you want a serious difference in quality, the hardware has to be much bigger, and that's the problem: they're trying to make it two things at once and, exactly as you might assume, it feels a bit like Frankenstein's monster."

Interview by Kit Buchan