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There's been some controversy surrounding the publicity camera samples for Nokia's new flagship smartphone, the Lumia 920. First it was shown (and admitted by Nokia) that the stabilised video footage wasn't shot with a Lumia, and now there are claims that the stills were also shot with a different camera, most likely a DSLR.

The basis for the stills claim is simply that starburst light diffractions as seen in the publicity shots only occur at very small apertures and would be impossible with the Lumia's fixed-aperture f/2 lens.

enter image description here

That assertion certainly matches my experience, but I'd still like to know: is there any way at all that starburst diffractions could be captured with a fixed f/2 smartphone lens?

I'm pretty sure the fakery claims will be substantiated, but I'd like to see them independently examined. For the record, I have no vested interest for or against Nokia, just a curious mind.

Update: I have no interest in conspiracy theories, broader discussions of advertising ethics or speculation of what kind of camera might have been used. Please keep answers on-topic and relevant to the question clearly stated in bold above: could such diffractions be captured by a small, fixed-aperture f/2 smartphone lens?

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    \$\begingroup\$ Shouldn't this be on skeptics.stackexchange.com ? :) \$\endgroup\$
    – Itai
    Sep 10, 2012 at 12:59
  • \$\begingroup\$ This is actually quite common for advertisements. In fact I'm surprised they didn't use medium format ;) The companies usually get to weasel out of their deception by stating the images were for "illustration only" and don't represent the actual output of the product. Oh and the burgers used in McDonalds adverts are usually uncooked in order to look bigger whilst satisfying that there was actually real food being shown. And the clothes used in the "after" shots of washing power commercials are brand new. \$\endgroup\$
    – Matt Grum
    Sep 10, 2012 at 13:59
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    \$\begingroup\$ I've made an edit to that title, it's far too provocative. Secondly, this is a Q&A site, not a rumour mill, can we keep it on-topic please? \$\endgroup\$
    – user9817
    Sep 10, 2012 at 14:13
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    \$\begingroup\$ If that's a fixed f2 lens then the depth of field looks substantially greater than I'd expect. By determining point of focus and location were visible un-focusing occurs you could determine if it was possible with the camera's lens. \$\endgroup\$
    – Russell McMahon
    Sep 10, 2012 at 14:17
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    \$\begingroup\$ It's amazing what people will read into a question. Please read it again carefully. It's not provocative, skeptical, naive or off-topic: I'm asking a purely technical question about whether the starburst diffractions COULD have been captured with a specific camera. The blog I've linked to boldly states that the diffractions MUST MEAN a Lumia was not used. I just want to know if that's verifiable. \$\endgroup\$
    – Mark Whitaker
    Sep 10, 2012 at 14:51

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One could achieve similar starbursts by holding a Star-16 filter (such as Cokin A055 or P055) in front of the camera phone lens. During a photoshoot aimed at demonstrating the camera's capabilities, however, the director of the shoot should consider that it's not what many phone photographers would do, so it would still count as deception.

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Yes there are many ways the starburst diffractions effects could be achived with a fixed f/2.0 lens:

  • Photographing the image projected by an SLR lens onto a groundglass. Products to achieve this used to be very popular with indie filmmakers to allow shallow depth of field (before the 5D mkII came along). Effectively provides the same image as you'd get with a large sensor DSLR.

  • Extra aperture stop placed in front of the lens in invoke diffraction.

  • Star burst filter in front of the lens.

It's worth reiterating that whilst technically possible all of these options represent a lot of effort to go to by the advertisers, with the only possible outcome of making the images look like they were faked!

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  • \$\begingroup\$ You've read the question wrong, Matt. I've updated to try and make it clearer. I only asked (very clearly, I thought): could such diffractions be captured by a smartphone lens fixed at f/2? I don't care what they were actually taken with. I certainly didn't ask for "definitive proof" of anything! \$\endgroup\$
    – Mark Whitaker
    Sep 10, 2012 at 15:00
  • \$\begingroup\$ @MarkWhitaker I've updated my answer to better represent what was actually asked! \$\endgroup\$
    – Matt Grum
    Sep 10, 2012 at 15:48
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The sunstar has 14 points, which means the lens used has a diaphragm with 7 blades. Unless a filter was used or the image was digitally manipulated, this wouldn't be possible with a camera with a fixed f/2 aperture. It would be difficult (but not impossible) to implement a diaphragm in a smartphone camera, but stopping down will likely degrade image quality due to diffraction limiting. See this Ken Rockwell article for details. (I know Ken Rockwell isn't always the most reliable or accurate source, but this particular article is accurate to my knowledge.)

Here's an example of what this looks like from my camera and lens using my flashlight (the DA 18-135mm has a rounded 7-blade diaphragm):

Pentax K-5 with Pentax DA 18-135mm @ 135mm. Av, 1/15s f/32 ISO 1600. Cropped and reduced in the GIMP. 14-point sunstars

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