At Holgarama the 2nd most common question we get customer asking is 'What is the difference between the glass and plastic lens on the Holgas?'. And I've we have answered 'not much' because from personal experience we've used a few Glass and Plastic lensed Holgas and I've had plastic ones that where much sharper than other glass ones, and really dreamy glass lenses, and all visa versa. It seems to depend on the camera it's self.
But we thought we better do a reasonably scientific test to make sure, as these where just personal feelings rather than anything backed up with any kind of evidence. So we put together a highly scientific test rig. In true Holga Style, basically we just glued a glass and a plastic lens Holga to a bit of wood and then used electrical tape to tape it to a tripod. To make sure the photos where both take at exactly the same time we attached a Holga Cable Release to each one. We then went off down to the seafront to shoot a roll of film and see what differences came up.
Please Note:The where taken on a day with horribly flat light which is why the colours look a little dull. We didn't want to do any post processing so we left them as is.
This shot shows very little difference in colours, contrast, brightness or vignetting. What is evident is that although both lenses have asharp centre the plastic lens goes soft much closer to the centre of the image. Also there is a fair amount of odd barrel like distortion on the plastic lensNote: Subject position is slightly off on the plastic shot due to the way the rig is setup
Again shot shows barrel distortion and that the plastic lens is softer on the outer edgers, but the glass lens also shows the softness as well, just not too the same degree as the plastic lens.
Show similar findings from shot 1 and 3
This shot shows a slight variation in the colour saturation in the green on the painting on the floor, but other than that there is little notice that hasn't shown up in the previous shots. .
As we originally thought there isn't much to choose between them, both produce very 'holgary' shots, there is very (if any) noticeable difference in the colours and contrast on each camera.
What does show up in the pictures is that the Glass lens have a much more overall sharpness, both have sharp centres and soft edges, but the sharp spot in the centre of the glass lens is much larger. So the plastic lens will probably produce more 'dreamy' shots overall.
There is also quite a lot of evidence to suggest that the plastic lens has a fair amount of Barrel Distortion, which we love, but other might.