Cheap (DIY) smartphone diffuser for light meter

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Conrad
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Ok - not sure if there is a thread this should go on, but I couldn't find one.

Anyway, as I'm just getting back into film, and there seem to be quite a few light meter apps for smartphones, I started looking for a suitable diffuser to use the incident metering mode which uses the front camera.

All I could come up with was the Luxi, which is available from Amazon for £46 for what is essentially a plastic dome and a clip.

Anyway, I started looking for suitable domes and found the following E14 LED bulbs sold as a pack of 2 for £6.40.
The diffusers are plastic, so with a small saw, a clip I found in my DIY cupboard and a little superglue, i now have a very basic diffuser that clips to my phone, and cost under a fiver.

Getting the dome to fix to the clip in the right place was just a case of putting the clip on the phone, then resting the diffuser next to it covering the front camera and attaching with a tiny spec of superglue (I only used very little to avoid getting the glue on the phone). Then when set, I removed the clip/diffuser from the phone and put a fair bit more superglue around the join to ensure it was very secure.

I'm sure there are better clips out there, so I may well make an improved version, and will be neater with cutting the diffuser next time, but it seems to function well and is ok as the mark 1 version.

Untitled by conradsphotos, on Flickr

Untitled by conradsphotos, on Flickr
 
That's very interesting - have you tested the accuracy against a proper light meter ?..

D
 
the apps ive played with can work it out with out a clip on dome, why have you made one? have your exposures been well out or is it more a bit of playing around?
tbh small exposure meters arnt very expensive and fit in your pocket anyway so doesn't the convenience aspect of using your phone get a bit pointless by carrying this. not a dig at you just cant see an advantage at the moment
 
Willid1 said:
That's very interesting - have you tested the accuracy against a proper light meter ?..

D
Click to expand...

I've done a few tests in a couple of different lighting situations, indoors and outside under an overcast sky, but only comparing with my Canon 5D3 in matrix mode.

The incident reading on the smartphone for the lightmeter app I'm using indicates around a half stop under what the camera meters. I'll do some more tests, and also see how it works in backlit situations.


niko said:
the apps ive played with can work it out with out a clip on dome, why have you made one? have your exposures been well out or is it more a bit of playing around?
tbh small exposure meters arnt very expensive and fit in your pocket anyway so doesn't the convenience aspect of using your phone get a bit pointless by carrying this. not a dig at you just cant see an advantage at the moment
Click to expand...

I read in a couple of places that the lightmeter apps on a smartphone can give inconsistent results in incident mode without a diffuser, so thought I'd have a go at making one mainly out of interest.

Fair point about the handheld meters - there seem to be a bunch of them around the £20-£30 mark, so apart from not having another device with batteries in, no real advantage to carrying the separate dome I guess.

Out of interest, as light meters aren't something I've used a lot, what is the actual difference between the £20-£30 variety, and the massive jump to the £100+ ones?
Something like
this cheap one compared to
this expensive one at pushing 10x the price?
 
C&C said:
Out of interest, as light meters aren't something I've used a lot, what is the actual difference between the £20-£30 variety, and the massive jump to the £100+ ones?
Something like
this cheap one compared to
this expensive one at pushing 10x the price?
Click to expand...

Neither of those seems designed for photogaphy. Rather than the expensive one, I'd get a Gossen or Sekonic with a more useful shutter speed/aperture/ISO/EV readout. But some people have used cheap Lux meters and done the relevant maths, e.g.:

https://SPAM/@rldm_/how-to-use-a-13-lux-meter-for-photography-61e798f27b01
 
ive got a cheaper sekonic, and a jessops own brand plus I've owned a couple of westerns in the past all gave good readings. the more expensive can have spot readings, or metre flash with obvious benefits.
out off the ones ive had the westerns were lovey to hold/use but no better readings than the two i own now.
 
Flash and diffuser and a pinhole, your maths must be better than mine Mr Watson!
 
I think it was the only camera II had with a pop up flash at the time and was going through a 35mm pinhole phase.
 
Just thinking about working out the exposure!
 
I hate smart-Phones... apart from the faff that they are looked on these days as sort of a hybrid swiss-army-penknife come Oracle of Delphi... my banana fingers cant work the damn things!

I recall a week-end in Derbyshire, with the daughter, and a lot of stops at the side of the road, with her yelling at me "Just wait! I need reception!" And being very hungry, when after riding past six pubs and the smell of their kitchens wafting our way, she insisted they didn't exist and were a figment of my imagination as they didn't come up on her list of recommended places to eat on google! THEN used her apps to lead me on a wild goose chase round the dales, with many a wrong turn and stop for reception to return, to find a Chinese restaurant that had been closed down for three years!!!! BUT it MUST exist... its in the google rankings!!!!!

Hmmm "Apple, you say? Let me show you how Isaac Newton discovered gravity.... pass me the apple, dear!" Lol.... seriously, after three days that was one bit of techno-geekery I was ready to lob off the highest fell I could find.... along with its over-enthusiastic operator!, Iactually!!! IBlame the hunger!!! But still....

Just as a complete counter point to the concept.... improvised engineering being interesting... my immediate reaction was.. a FIVER?! And all that polava?! I only paid that for a pristine Leningrad V off e-bay a couple of years ago... tooo many things with batteries? Pah! Leningrad's a selenium cell meter! No batteries required!

It DOES seem a rather involved, convoluted, time consuming, unreliable, and more expensive solution to the problem! Especially when for no money, no faff, you can use your EYES and apply the f-16 sunny Rule of Thumb to the job... which has always worked well for me, when I have had meter-less cameras, or found the inver-cone missing from its pocket or whatever!

Does make me ponder the potential 'fun' to be had with a LDR, a PP3 and some components from Maplins, wiring them together in a Wheatstone Bridge, to make my own light-meter... without the unnecessary convolution of an Oracle of Apple attached.... but one for academic interest only, me-thinks!

If 'stuck' say batteries flat on a sektronic or a weston's gone west; notion of using a smart phone, may have some merit, and there, maybe sticking a petrol station receipt over the CCD to improvise the invercone, would sort of make sense.... but, sorry, to make an accessory invercone, to be able to use a smart-phone, as first course?!?!? Just seems a very very perverse way about solving the 'problem', if it even really is one, whilst perpetuating this smurfone dependency, and idea that they 'must'; be part of the solution to well, EVERYTHING! To my mind.
 
...and for the paupers..no one has mentioned a Kodak grey card (OR EQUIVALENT) as a film camera meter reads 18% grey, it's accurate if you position it right facing the camera e.g. a portrait, card vertical if person is upright or card horizontal if lying down. Looked on the bay and thought there was a bargain with grey, white and black bits of plastic, on a key ring, for £1.69 with free postage but erm shiny surface? and can't see it being of much use as it's too small. If you are just going to use B\W and colour neg....a light coloured grey bit of cardboard would do or have noticed light grey undercoat paint looks about right so make your own. So how do you know you have an equivalent of a Kodak grey card ? well just compare with a picture (for colour density) on your computer screen.
Incidentally as a film meter can't see colour, any colour would do e.g. green, blue, red etc as long as it read the same as Kodak grey...and sometime when stuck for meter reading on a sunny day have metered the blue sky or green grass\shrubs....clever Kodak for thinking of 18% grey as it covers a lot of things in your shot so most joe public's shots come out well (y)
But incident or reflective from a grey card is not the perfect solution all the time as if you scene includes some important shadows too far away, it's not convenient to run over to the shadow bit and take a grey card reading, so experience does help to get the exposures right in your shot. And using a spot meter, If buildings are in shadow, helps as the grey building would be roughly Kodak grey.
Anyone disagree with my camera use and thinking?
 
1. Meters (according to the standard) should be calibrated for 12% grey, which apparently is why Kodak say that the 18% card should be angled to the light source. Possibly appocryphal, but someone somewhere said Kodak chose 18% to satisfy Ansel Adams...

2. Causcasian palms are fairly standard in reflectance, so metering from the palm of your hand and opening up one stop works. If the subject is in shadow, put your hand in shadow; if in the open, put your hand in the sunlight.

3. Some types of exposure meter are overly sensitive to red, and metering through a red filter can lead to underexposure, so don't assume a spectral response without checking it.

4. Incident readings (which to me include grey cards, palms of hands and even white handkerchiefs - I've used one in dark conditions, with appropriate compensation) are the safest way of avoiding blown highlights with reversal films.
 
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