iPhone 5s camera sensitivity

[Photosbykev]

can anyone point me toward some data on the iPhone 5s sensor please, I'm curious what it is capable of capturing as a widefield astro camera. I know it isn't great but I'd like to put a real number on it, maybe the lowest achievable star magnitude?

[JRWASTRO]

can anyone point me toward some data on the iPhone 5s sensor please, I'm curious what it is capable of capturing as a widefield astro camera. I know it isn't great but I'd like to put a real number on it, maybe the lowest achievable star magnitude?

Greetings Kevin,

I just found some very basic stuff on the sensor in question:

http://www.imore.com/iphone-5s-preview-isight-camera

How good is it going to be for astro photography? The basic data ( 1.5 micron pixels and an f/2.2 aperture) indicates that getting good pictures may be a challenge.

Re:  " I'd like to put a real number on it, maybe the lowest achievable star magnitude?  "

The answer is complex as it involves estimating the Signal to Noise Ratio (SNR)  of the signal (for each pixel) from the photo site amplifiers as a function of received SNR (photon signal that varies as the exposure, type of optic etc). This takes into account the noise produced by the amplifiers, readout noise, etc, etc, etc.  End result is that we estimate an SNR for a given stellar magnitude and make a judgement of quality based on required SNR. Say we get a raw SNR of 0db (signal and noise are equal) is this "good enough" ? How many images do we need to stack (integrate) to improve the estimate? ... Sounds awful? Doesn't it ?

Well, all is not lost. Point the camera to Vega and exposure a few frames with different exposures and see what the image of this star is. Then compare the Vega image with the image from another star and see how you go.

Sadly putting numbers to things gets rather painful.

Why choose Vega to test?

Vega is used as the 'standard' for matching the magnitude scale to fluxes.

- Total flux for a star  (Mag = 0.0) = 1.27E-8 W/m2

- A 5 Magnitude change = x 100 in flux

- eg. A mag 10 star produces a flux of 1.27E-12 W/m2 (a smalish number !)

Good luck

Jeremy.

PS.

Many moons ago I gave a talk on f-number and posed the same question as you asked.  On slide 11 (of 14) I asked the same question of the audience. If you would like a pdf version of the slides please say so.

JRW.

 

[Stu]

Just to say (and I'm probably stating the obvious), but there are apps available which give much better manual control of the camera I believe.

Sent from my iPhone using Tapatalk

[Photosbykev]

Thanks for the input gents, Jeremy I'd like to see the pdf please (kevin@photosbykev.com), BMS there are apps and I have a few but IMHO all they create is a star field comprising of noise not stars sure Vega can be captured but not a lot more PS it isn't something I want to do but sometimes people need a bit of a reality check

sent from my Sony Xperia Z2

[JRWASTRO]

Thanks for the input gents, Jeremy I'd like to see the pdf please (kevin@photosbykev.com), BMS there are apps and I have a few but IMHO all they create is a star field comprising of noise not stars sure Vega can be captured but not a lot more PS it isn't something I want to do but sometimes people need a bit of a reality check

sent from my Sony Xperia Z2

*.pdf file sent. Hope it is of use. I could present it here but I did not include the reviewers comments nor address his criticisms I took note and altered the talk accordingly.

OK one can capture Vega to get other stars (choose the bright stars) increase the exposure times and examine the pics. The times and ratio of the times may be used to get a "guesstimate" of what one may see with a given exposure.

I do notice that people produce excellent pictures with these smart phone cams. Tells one more about the talent of the photographer than the camera!

Jeremy.

[Photosbykev]

Thank you Jeremy

sent from my Sony Xperia Z2