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USB Fever iPhone Polarising Filter Review

USB Fever iPhone Polarising Filter Review - We review a mini circular polarising filter for the iPhone 4/4s.

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Mini Circular -PL Filter in Filters

Handling and Performance

The USB Fever Mini Circular-PL Filter is a circular polarising filter for use with the iPhone 4 and iPhone 4s. A polarising filter is used to reduce reflections on non-metallic surfaces. It's ideal for shooting through glass when the reflection prevents you seeing what's behind. It also allows you to record what's below the surface of water, and the glare reducing factor makes colours more saturated.

The filter with back case costs $38 from USB Fever (or around £27 in the UK via eBay).

USB Fever Polariser

USB Fever Mini Circular-PL Filter Features

The filter comes with a standard iPhone back cover case that has a screw thread hole positioned over the phone's camera lens. The filter screws into the threaded hole so it sits over the lens. The thread is the same size as the USB Filter's lens attachments so the case can be left in place and lenses switched as necessary.
  • Lens Construction: 2 elements in 2 groups
  • Metal mount
  • Glass filter
  • Dimensions: 19.5mm (diameter) x 7.0mm (length)
  • Weight: 3g (lens)
Attaching USB Fever Polariser to case

USB Fever Mini Circular-PL Filter Handling & Performance

Although the filter is tiny it's easy to attach, but care does need to be taken when screwing it into place to avoid cross threading as the metal thread filter could strip the plastic case's thread if aligned incorrectly.

Rotating USB Fever Polariser

Once in place the filter can be rotated and has a knurled rim to make it easier to grip. It works just like the polariser your use on a standard digital camera and increases saturation while reducing reflections. You can even shoot the cross polarised colours in plastic when using your computer's LCD screen as a background. See article here: Cross Polarisers

The polariser normally has a filter factor which means you have to adjust exposure to compensate. This is usually between one and one and a half stops. As the iPhone is totally automatic you don't need to worry about this, In one of our tests it increased the ISO to compensate from ISO800 to ISO1000. When the filter is attached it makes no difference to exposure when adjusting the filter position.

On the shot with the apple you can see that in the first shot the worktop is darker because the angle means the polariser has killed the glaer there. While on the second shot it's reduced the reflection in the tiles, but has no affect on the worktop. With the glass bottle shots the polariser has dulled down any glare reflections in the glass.

The one main flaw with the filter is it's not wide enough diameter which means the lens sees the edges and results in dark corners or vignetting. This can be cropped off but does mean you're not getting the full capacity of your camera and you'll need to compensate when framing to prevent important detail being clipped when you crop later.

USB Fever Mini Circular -PL Filter Sample Photos

USB Fever Mini Circular-PL Filter Verdict

It feels a bit cheap and plasticky (despite having metal mount), but the filter delivers the results and that's the important part. With the polariser in place you can enhance your colour photos from the iPhone. It's a shame about the vignetting, otherwise a filter that's well worth considering if photography is a regular activity from your phone use.

USB Fever Mini Circular-PL Filter Pros

Works well to reduce reflections
Reduces glare to increase colour saturation
Comes with iphone case
Doesn't add too much extra bulk

USB Fever Mini Circular-PL Filter Cons

Vignetting in corners of frame
Plastic thread of the case could get damaged by cross threading


For more details of the iPhone Polariser visit USB Fever.

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