LCG or HCG

[Howardk]

I’m confused between the read modes of LCG and HCG

does sharpcap automatically set this for my mallincam DS26c based on the gain setting i choose or do i have to manually select LCG or HCG and if so when do i make this decision and why?

[admin]

Hi,

if you are using a ToupTek built camera (Mallincam, Altair, Omegon, many other), SharpCap will try to merge the LCG/HCG switch into the gain control and manage the changeover automatically for you. This depends on SharpCap recognising the camera model and therefore knowing the sensor model inside the camera and how the LCG/HCG switchover works for that sensor.

If you see a 'Read Mode' control with options for LCG and HCG then the option is in manual control (because SharpCap hasn't recognized the camera model or sensor). If you don't see that then the LCG/HCG switch is handled automatically for you as the gain is adjusted. SharpCap will apply HCG at the lowest gain value compatible with using it, as it almost always gives better results (reduced read noise) compared to LCG at the same total gain. For the common IMX571 sensor, the changeover happens at gain=300.

If you prefer manual control and are using an up-to-date version of SharpCap 4.1, you will find an option in the main SharpCap settings to take manual control of the LCG/HCG switch - change this option and re-open the camera and you should have manual control.

cheers,

Robin

[Howardk]

Robin

My mallincam has gain up to max 10,000
The change from lcg to hcg automatically kicking in for sensor imx571 at gain 300 seems very low….

My mallincam which has the 571 sensor has the read mode switch in sharpcap and i have it set on hcg

Does the gain scale vary for different cameras??

[admin]

Hi,

gain is an awkward control because it is treated differently by different manufacturers. For ToupTek made cameras like your Mallincam, the gain minimum of 100 can be thought of as 100%, then a gain of 200 means that the image is twice as bright (200%) as at gain 100, etc. Other brands of camera like ZWO or PlayerOne use a scale based on 0.1dB unit, so their scale is logarithmic not linear... This means you can't compare values between different brands without being aware of these subtleties. Even within a brand, the maximum gain does vary from model to model.

For your IMX571 (all IMX571 for that matter), the change from LCG to HCG brightens the image by a factor of 3. That means that if you want an image 3x brighter than minimum gain, you can either

* Use LCG and set the raw camera gain to 300

or

* Use HCG and set the raw camera gain to 100

Both of these give the same brightness of image, but the second option has much lower read noise which means it will produce better deep sky images (given the same exposure length), or let you get away with shorter exposures and still get the same quality. That's why SharpCap will switch to HCG as soon as possible.

Basically, the idea of having the LCG/HCG as part of the gain adjustment is to always give you the optimal settings for a given gain value, without you (the SharpCap user) having to know/care/do reasearch into the difference between LCG and HCG and which should be used.

cheers,

Robin

[Howardk]

Robin

I don’t think a Mallincam has anything to do with a ToupTek made camera

I also am not sure if gain set at 100 in HCG mode will be enough when the maximum setting goes to 10,000

Will have to check when the weather clears