Sony A5100 - Don't buy for astrophotography

[MarkS]

I was running through a batch of tests on my Sony A5100 this evening and then hit the showstopper

Long exposure noise reduction cannot be switched off.  So after, for instance, a 5 minute exposure it automatically takes another 5 minute (dark) exposure to subtract.  This functionality cannot be switched off.

http://community.sony.com/t5/Alpha-SLT-DSLR-Cameras/Can-Long-Exposure-Noise-Reduction-be-turned-off-on-the-A5000/td-p/481306

This applies to the A5000 and the A5100.  You have to buy the A6000 (same sensor as the A5100) to be able to switch this off.

Mark

[Mike]

DOH!!!   

[The Thing]

You should be able to send it back under the 'not suitable for the purpose intended' clause. Your purpose might take a bit of explaining  though - ripping it apart and taking out a fundamental part!

[RobertM]

Difficult to believe - I would have fallen into the same trap myself.

Talk about removing decisions from photographers - they might as well set noise reduction to max and disable any control !

As Duncan has mentioned, Amazon are good at taking things back.  I hope that is a painless process.

Robert

[MarkS]

You should be able to send it back under the 'not suitable for the purpose intended' clause. Your purpose might take a bit of explaining  though - ripping it apart and taking out a fundamental part!

 

My purpose is long exposure photography using Bulb mode in the same simple way that cameras have done for over a century.  That really isn't an unreasonable thing to ask.

Imagine if they changed something that fundamental in the car industry and Ford brought out a car which slows down when you press the accelerator too hard!

Mark

[Mike]

It annoys me when they do things like this. Especially when you are literally talking about 3 or 4 lines of extra code in the firmware for something so simple. It's just ineptness.

[Carole]

Are you going to be able to get a refund Mark?

Carole

[Kenny]

If you bought this on Amazon you should be ok. I've never had any problems returning stuff to them, always get a full refund.

[The Thing]

It annoys me when they do things like this. Especially when you are literally talking about 3 or 4 lines of extra code in the firmware for something so simple. It's just ineptness.

More like they added extra code to restrict access to features based on model.

[RobertM]

It annoys me when they do things like this. Especially when you are literally talking about 3 or 4 lines of extra code in the firmware for something so simple. It's just ineptness.

More like they added extra code to restrict access to features based on model.

And that's no joke, they do that

[MarkS]

Here are some counterintuitive results from my testing.

Recall that Sensorgen http://www.sensorgen.info/ states Quantum Efficiencies of 41% and 61% for the Canon 550D and the Sony A5100.  I didn't have an unmodded 550D available so I tested with a 600D which is more or less identical.
Comparing the Sony A5100 and the Canon 600D side by side I reach the following conclusions.
1) In the Blue and Green channels the A5100 collects only 25% more photons than the 600D.
2) In the Red channel there is no difference at all. I suspect the same is true at the H-alpha wavelength.

In terms of read noise and dark current there is very little between them.  Conclusion, I don't think that the Sony A5100 (nor, by implication, the Sony A6000)  represents a noticeable improvement for astrophotography.

3 other points of interest:
1) From the Canon 300D up to the Canon 600D and including the Sony A5100, dark current per pixel has remained more or less static.  In the same time, pixel count has increased from 6Mpx to 24Mpx.  So dark current over the total sensor area has quadrupled over time  [Correction: the dark current per pixel has halved, which means the total sensor dark current has doubled].  This is not a good trend and it is not measured by DXOMark/Sensorgen
2) From the Canon 350D up to the Canon 550D, QE has certainly increased but only in the Green and possibly Blue regions of the spectrum.  The 350D and 550D has identical responsiveness to H-alpha.  Probably the Sony A5100 as well.  The sensor taken as a whole captures the same number of H-alpha photons.
3) My 600D vs A5100 test again supports my long held belief that something in the Sensorgen methodology understates the QE performance of Canons

Mark