SLR lens on a phone, how?

Started Dec 1, 2011 | Discussions
sidneylopsides New Member • Posts: 2
SLR lens on a phone, how?

Right, I had the idea a while back to create an adapter so a large lens could be mounted on a phone to give extra options, and the strong DOF you see on larger cameras.

Then yesterday I noticed someone has made an entire feature film with an N8 and a lens adapter.

As I now know it's possible, and have an idea of the results, what are the actual parts needed to do this?

I have a few old manual Pentax K lenses, and I've ordered a lens mount plate to attach to a spare back cover of the phone.

The difficulty is adapting the optical part. Somehow I need to get the camera focussed on the image from the lens, without the circular crop.

I'll be using an Xperia arc or neo, they have an equivilent FOV of 28mm, as far as I've worked out, and a focal length of 4.1mm. I assume for ease setting the phone to focus on infinity is easiest, if that would work.

Does anyone have any ideas how to make this work?

Thanks!

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Jeff Peterman
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Re: SLR lens on a phone, how?

The DOF is not related to the lens as much as it is due to the tiny sensor. You'll have to put a huge amount of effort into this to get a very poor result if your main aim is to improve the DOF. Is it really worth the effort compared to just buying a P&S with a decent lens?
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SamTruax Senior Member • Posts: 1,774
Re: SLR lens on a phone, how?

There are a number of companies that offer DOF adapters for the iPhone and they seem to work quite well. If you do a Google serarch you will find a few of them. For the most part they only have lens adapter options for Canon or Nikon lenses but you could probably rig something up yourself or even get a Canon EF to whatever other mount adapter and add that into the mix.

DOF is dependent on sensor size but these adapters are quite ingenious in their design and they seem to do the job pretty well. The examples I have seen have used the Canon 50 1.8 and they look good.

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OP sidneylopsides New Member • Posts: 2
Re: SLR lens on a phone, how?

Thank you! Found some guides, and using some spare parts and an old broken Centon I have a rough build that works.

Now I just need to make it properly (not using bits of card!) and get a plain focus screen.

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Wayne Larmon Veteran Member • Posts: 9,798
You can get true shallow DOF with a camera phone

Jeff Peterman wrote:

The DOF is not related to the lens as much as it is due to the tiny sensor. You'll have to put a huge amount of effort into this to get a very poor result if your main aim is to improve the DOF. Is it really worth the effort compared to just buying a P&S with a decent lens?

Apparently it was for the people that shot the movie that the OP referenced. The trick is to mount a ground glass between the 35mm lens and the camera phone. The image is formed on a FF sized portion of the ground glass, and hence, has the same shallow DOF that you'd get if the lens was mounted on a FF camera. The camera phone focuses on the ground glass.

The lens/camera phone looks like this

This article about the making of the movie has a video. The first part of the video goes into how they made the movie (including the explanation of the lens/ground glass that I paraphrased.)

http://www.reghardware.com/2011/12/01/smartphone_shot_movie_guns_for_cinema_release/

The second part of the video is the first five minutes of the movie. So you can see for yourself how well the phone camera worked.

I'll leave it to you to decide how practical this is.

Wayne

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