SharpCap Forums

Hi Robin
Thanks for the quick reply - just what I needed for clarification.

Thank you
Matthew

Hi Robin,

Why is the switch between LCG and HCG done automatically?
So, when SharpCap turns the HCG on, what exactly happens in the „sensor driver“? My understanding is that from gain 100 to 300, the „internal“ gain ist set to the gain setting with HCG off. From 300+, the internal gain setting is set back to the smallest value but HCG on?

As far as I get it, the amplifier gain and LCG/HCG are decoupled settings within the sensor‘s hardware driver.

I‘m using both NINA and SharpCap and the different behavior (without any judgement of course) confuses me a bit.

My gain setting approach also follows yours, which is using the lowest gain for max dynamic range but with the HCG mechanism one can lower the read noise significantly without losing (any significant) DR under low light conditions. It’s not my goal of imaging with unity gain or any other arbitrary and „meaningless“ setting.

CS, Björn

Hi Björn

using the HCG/LCG switch, you can arrive at most gain levels (gain as in brightness boost amounts) above the HCG minimum in two ways

* Using HCG and a smaller gain value - for instance HCG and gain 150 to get a total gain of 4.5x
* Using LCG and a larger gain value - for the same gain of 4.5x you would use a gain of 450 in LCG

Given the way that the read noise on these sensors varies, the first option invariably has lower read noise, usually by a considerable amount - this allows shorter exposures to be used with no sacrifice in image quality, or provides better image quality in the final stacked image if short exposures are already in use.

For every SharpCap user like you who thinks carefully about LCG/HCG and which to use, there will be at least 10 who haven't heard of it before and would have no idea which option to choose or why if presented with a separate choice. Since SharpCap is supposed to be about making imaging easier, making the right choice in terms of HCG/LCG automatically is a beneficial feature for most people.

On top of that reasoning, there is also the fact that changing the behaviour now would cause problems for thousands of people who already use SharpCap and are used to picking a particular gain for a certain type of imaging.

cheers,

Robin

Hi Robin,

Thank you very much for your reply!

Your explanation makes sense to me with respect to the ease of use for many users. My question wasn't meant to be a critique and I hope you didn't understand it as such. Otherwise, my apologies!

So, if I understand the previous posts correctly, the HCG for the Hypercam 533C will be turned on at gain 300, and not at 200, with recent versions of SharpCap? (On the Altair website, they're showing a sensor analysis which indicates the HCG turning on at gain 200)

CS, Björn

Hi Björn,

yes, recent versions of SharpCap turn on HCG at gain 300 for the IMX533 and IMX571 - the older versions turning it on at gain 200 was an error

cheers,

Robin