metering - How well do smart phone light meter apps work? - Photography Stack Exchange


smartphone light meter

Jul 17,  · A retro light meter for Android and iOS smartphones There are thousands of apps to measure light, but few offer both the functionality of a light meter and the classic shape of an old style light metering device: that’s what makes David Quiles app unique. Jose Antunes July 17, Oct 10,  · However, you have to buy the $22 Luxi For All Smartphone Attachment in order to use the app as an incident meter and to measure ambient light levels. This app gives very accurate light and color readings, and you can even use the Luxi For All attachment in conjunction with the Pocket Light Meter and Cine Meter II to measure light in different. Sep 19,  · This item: Luxi for All - Smartphone Light Meter Attachment. Set up a giveaway Customers also shopped for. Page 1 of 1 Start over Page 1 of 1. This shopping feature will continue to load items. In order to navigate out of this carousel please use your heading shortcut key to navigate to the next or previous heading/5(79).

Luxi For All | Light Meter Attachment for Smartphones

I will not budge on two things. Second, smartphone light meter are not light meters. Say it again with me. Smartphones are not light meters. Yes, again, but with feeling this time. There are dramatic differences between smartphone smartphone light meter meter apps and standalone light meters when used in the lighting world.

A light meter is smartphone light meter tool that measures illuminance. It has units of lumens per square foot footcandles or lumens per square meter lux. These apps were originally intended to help photographers configure their fancier DSLR cameras to take photos that are well exposed — not too bright, smartphone light meter, not too dark.

Photographers can use an independent light meter to configure their camera. But a light meter is not a mission-critical device for most folks. Lighting professionals have a lot in common with photographers.

A camera for documentation. A tape smartphone light meter or laser range-finder for distances. And of course, our phone for sharing what we had for lunch … I mean for contacting site personnel.

Lighting professionals deal with mission-critical lighting measurements that have implications for smartphone light meter and public health. Our light meters may be used to evaluate sufficiency of egress lighting, calibrating or smartphone light meter a lighting control system, evaluating whether a contractor or start-up agent has done their job adequately, or whether they need to revisit the site for additional modifications. An energy auditor may use it to help decide what areas could be delamped or retrofit with a new luminaire.

These measurement scenarios have real-world, bottom-line repercussions if the measurements are not right. There are two relatively good efforts in this space. DIAL, a European software firm associated with DIALux, did a great bench-top experiment that found most smartphone and app combinations did a pretty poor job measuring light, smartphone light meter.

Another study from Diogo Cerqueira, Pilipa Carvalho, and Rui Bettencourt Meloall three out of Lisbon, did a more comprehensive, scientific study comparing multiple smartphone illuminance meters and their summary chart is just beautiful in its simplicity and impact. Cerqueira et. In this chart, the calibrated meter reading is measured on the x-axis and the app results are reported on the y-axis. At lux 30 fc and lux 50 fcthe apps report between smartphone light meter lux 2 fc and lux fc.

Light meters generally include three key photometric i. These three components must be designed and specified for one another. The cosine correcting lens must be sized to fit the light sensor.

And the smartphone light meter has to output a range of values that can be measured accurately and repeatedly. This is no small task, smartphone light meter. A light meter app incorporates two components — the physical measurement using the phone camera and the software processing of the camera output.

Smartphone Light Meter Process. To render images well, the camera minimizes smartphone light meter barriers between the environment and the image sensor. As a rule, cellphones prefer transparent screens. The glass screen minimally distorts the light coming-in, but it does not offer a cosine correction. Some light meter app proponents have tried to solve smartphone light meter problem with a snap-on cosine correcting lens ; however, the exact photometric performance is hard to verify.

The glass on cameras tends to have a specular surfacewhich generally redirects low angle light, while high angle light tends to pass through to the sensor easily. Even though we wish to discount low-angle light sources, we cannot ignore it all together. When the cellphone camera is active, an image is recorded on the charge-coupled-device CCD or complementary metal-oxide sensor CMOSas each individual photon impinges on each sensor.

Each unique sensor will have a specific sensitivity to the spectrum of light it is most sensitive. Given the sheer breadth of cellphones available, smartphone light meter is very unlikely app programmers are characterizing individual sensors. Furthermore, many camera manufacturers regard the spectrum sensitivity and filtering approach to be a trade secret, obscuring the accuracy of what the sensor is physically metering.

Even among professional Smartphone light meter cameras, there are significant differences between individual camera sensors — different between brands and even models.

Depending on the mobile platform e. Apple vs. Androidthe ability to send API calls from the app to the camera mostly a function of programmer effort on modern mobile platformsand the programmed camera response; the settings for the aperture, smartphone light meter, shutter speed, and ISO setting could all result in some degree of over- or under-exposure of the camera sensor, providing flawed data to the app.

Each pixel of data is encoded in to an RGB value normalized betweenoften referred to as the sRGB transfer function, smartphone light meter, or gamma.

This normalization process creates a potential resolution errors constraining an analog value to an 8-bit digital structure. Depending on the phone manufacturer, smartphone light meter, the transfer function may enhance certain regions of the spectrum to make colors in images appear more vibrant or prettier on the phone screen, smartphone light meter.

This vibrancy-enhancement makes pictures look attractive to consumers, but distorts the scientific measurement of light, smartphone light meter. Depending on how the camera manipulates the image smartphone light meter, the camera may store the file as a. The compression process usually further distorts the accuracy of each RGB channel.

While DSLR cameras support. Changes in sensitivity functions due to file compression for 3 DSLR cameras [iii]. Each sensor has many, many individual pixels usually measured in millions, i. The cellphone app then performs mathematic averaging function, grouping pixels together and using a well-known transformation to covert individual RGB coordinates into CIE-Y, which is a spectrum weighting function very closed to the photopic sensitivity curve, smartphone light meter, V lambda.

If your space does not have a uniform color temperature say a office adjacent to a window, with 3,K electric lighting and 6,K from daylightthe averaging of the various pixel groups may not accurately measure what the human eye perceives in the space. With each of these steps, tiny errors are injected into the process. One or all of these factors could bias the reading of the light meter app and generate a false reading.

A smartphone does a lot of stuff in the field. It can take pictures, record field notes, and doubles as a reasonably good bubble level. A smartphone is not a light meter. A lighting professional — be they a designer, consultant, manufacturer rep, installer, or start-up technician — has too much on the line to draw conclusions based on a faulty light meter.

Light meter apps based on my experience and the experience of others fail to correctly measure light when compared to calibrated light meters designed for that purpose. Avoid the guess work and invest in a good light meter and treat it gently. How do you buy a good light meter? Like this post? Share it on Smartphone light meter. Carvalho, F. Illuminance for Occupational Health and Safety Purposes? Jiang, D. Liu, J. Gu and S. No Comments. How can we help you save money and lower your carbon footprint?


Don’t ‘Phone It In’: Why Smartphones Are Poor Substitutes for Light Meters - kW Engineering


smartphone light meter


Jun 28,  · A smartphone is a powerful tool for any photographer, whether you’re using it to take pictures or make shoots are countless different apps that can make your phone into almost any photo-gadget imaginable. In this tutorial, you'll learn how to turn your phone into a reliable light meter. The light meter built into cameras measures reflected light. A reflected light meter shows an appropriate setting for an average of the whole scene. If you are taking a picture of a scene that does has neither an average, nor internally consistent lighting situation, your camera's built-in light meter . Oct 10,  · However, you have to buy the $22 Luxi For All Smartphone Attachment in order to use the app as an incident meter and to measure ambient light levels. This app gives very accurate light and color readings, and you can even use the Luxi For All attachment in conjunction with the Pocket Light Meter and Cine Meter II to measure light in different.