Taking Flats in Current Version of BYE

[rockstarbill]

Hey all,

 

Looking for some up-to-date guidance on taking flats in BYE. I read through the older threads on this, and it seems that using AV-Flat is the setting I want. There was some discussion about the histogram using the JPEG image and not the RAW, has that been resolved? If not, what is the best way to take good usable flats in BYE? I am on the trial right now, and this is an issue that could be a deal breaker for purchase. I could always look at the stats in Nebulosity (or just take the flats there) or PixInsight, but that kind of defeats the purpose IMHO.

 

Camera is a Hutech 6D, in case that matters...

 

Clear Skies,

Bill

[admin]

No worries...

 

TV means Time Value... it's a shutter speed.  You have Bulb, TV up to 30 seconds, and AV which lets the camera decides the TV exposure duration.

 

AV-Flat = camera decides the TV exposure duration.

TV = you decide so you can increase the duration.

 

Hope this helps,

 

Regards,

[admin]

Use a TV value instead of AV-Flat; that gives you more control.  Push this histogram until it is about 2/3 in from the right.  That should do it.

 

Yes, the histogram is still using the embedded jpg.  If you feel you need to expose more increase the TV duration until the histogram is to the far right but make sure the hump is still withing the grid area.

 

Regards,

[rockstarbill]

Use a TV value instead of AV-Flat; that gives you more control.  Push this histogram until it is about 2/3 in from the right.  That should do it.

 

Yes, the histogram is still using the embedded jpg.  If you feel you need to expose more increase the TV duration until the histogram is to the far right but make sure the hump is still withing the grid area.

 

Regards,

 

Sorry for my ignorance, but what do you mean by TV value?  

 

Thanks for responding, I enjoyed the 2 hour long video you posted. That is quite informative! 

[rockstarbill]

No worries...

 

TV means Time Value... it's a shutter speed.  You have Bulb, TV up to 30 seconds, and AV which lets the camera decides the TV exposure duration.

 

AV-Flat = camera decides the TV exposure duration.

TV = you decide so you can increase the duration.

 

Hope this helps,

 

Regards,

 

Thanks! That should do the trick then! 

[astroman133]

Tv means "shutter priority". When shooting with a lens, you set the exposure time and the camera adjusts the aperture (f/stop) to achieve the correct exposure.

 

The Av Flat shooting mode lets the camera's exposure meter decide the exposure for you.  It may be useful, especially if you are using a constant, artificial light source, to get an initial exposure.  Then you could change to manual mode and tweak that exposure to get the right histogram for your flat frames.

 

Tv means "shutter priority", as opposed to Av which means "aperture priority". What Guylain is saying is that you should adjust the exposure duration yourself to get the correct histogram for your flat frames.

 

Also, your stacking software will dictate the requirements of the flat images, but typically you should use the same image type (Raw or Jpeg) as your lights. I strongly recommend shooting only RAW for all image types. But would especially recommend not trying to mix JPG flats with RAW lights, even if your stacking software allows it, which it probably won't.

[rockstarbill]

Tv means "shutter priority". When shooting with a lens, you set the exposure time and the camera adjusts the aperture (f/stop) to achieve the correct exposure.

 

The Av Flat shooting mode lets the camera's exposure meter decide the exposure for you.  It may be useful, especially if you are using a constant, artificial light source, to get an initial exposure.  Then you could change to manual mode and tweak that exposure to get the right histogram for your flat frames.

 

Tv means "shutter priority", as opposed to Av which means "aperture priority". What Guylain is saying is that you should adjust the exposure duration yourself to get the correct histogram for your flat frames.

 

Also, your stacking software will dictate the requirements of the flat images, but typically you should use the same image type (Raw or Jpeg) as your lights. I strongly recommend shooting only RAW for all image types. But would especially recommend not trying to mix JPG flats with RAW lights, even if your stacking software allows it, which it probably won't.

 

I use PixInsight and I only shoot in RAW mode. Once the skies clear up I will give this a go and see how it does. I use T-Shirt flats.

[s3igell]

Also, realize that the "Rule of Thumb" about Flats needing to be of a specific ADU Range are rather Outdated.  That Rule was developed at a time when most of the Sensors were Early / Low-priced CCDs which had significant Linearity Issues.  These days, all DSLRs and most CCDs have Very Wide Linear Regions.  So, the reliance on Near-Exact Histogram Placement is not as Critical.

[rtemen]

Use a TV value instead of AV-Flat; that gives you more control.  Push this histogram until it is about 2/3 in from the right.  That should do it.

 

Yes, the histogram is still using the embedded jpg.  If you feel you need to expose more increase the TV duration until the histogram is to the far right but make sure the hump is still withing the grid area.

 

Regards,

I see that Bulb, Tv and Av are all mentioned several times. I cannot find Tv anywhere.

Is there a tutorial on how to use Tv?

Rich

[astroman133]

Rich,

 

Tv is a photographic term that stands for Time Value. In normal terrestrial photography it is a shooting mode where the shutter speed is fixed by the photographer and the aperture (f-stop) is altered by the camera's processor to give a correct exposure. Of course, this only makes sense when using a lens that supports a range of f-stops. When the camera is connected to a telescope, the aperture is fixed.

 

Tv mode is different from BULB mode, although both modes fix the exposure duration in advance of shooting. In BULB mode the shutter is controlled externally from the camera; like with a remote shutter, interval timer, or computer. BULB mode is typically used to provide exposures longer than 30 seconds, as is common for astrophotography.

 

When Guylain says to "use a TV value" what he is saying is to choose a numeric shutter value (not BULB, AV-Flat, or Program) from the Shutter dropdown list in BYE's Capture Plan Center. That shutter value would be somewhere between 30 seconds down to 1/4000th of a second (or shorter, if your camera supports it).

 

When BYE shoots a 2 minute BULB exposure, it issues a command to open the shutter and 2 minutes later it issues a command to close the shutter. When taking a 1/2 second Tv exposure, BYE tells the camera to take the 1/2 second exposure and the camera controls the opening and closing of the shutter.

 

For shooting flat frames you would take a series of pictures while varying the shutter value to shift the image's histogram so that the left-to-right position of the peak of the hump is slightly above the middle. The longer the exposure the brighter the image and the further to the right the histogram peak should be.

 

I hope this helps.

[rtemen]

Rich,

 

Tv is a photographic term that stands for Time Value. In normal terrestrial photography it is a shooting mode where the shutter speed is fixed by the photographer and the aperture (f-stop) is altered by the camera's processor to give a correct exposure. Of course, this only makes sense when using a lens that supports a range of f-stops. When the camera is connected to a telescope, the aperture is fixed.

 

Tv mode is different from BULB mode, although both modes fix the exposure duration in advance of shooting. In BULB mode the shutter is controlled externally from the camera; like with a remote shutter, interval timer, or computer. BULB mode is typically used to provide exposures longer than 30 seconds, as is common for astrophotography.

 

When Guylain says to "use a TV value" what he is saying is to choose a numeric shutter value (not BULB, AV-Flat, or Program) from the Shutter dropdown list in BYE's Capture Plan Center. That shutter value would be somewhere between 30 seconds down to 1/4000th of a second (or shorter, if your camera supports it).

 

When BYE shoots a 2 minute BULB exposure, it issues a command to open the shutter and 2 minutes later it issues a command to close the shutter. When taking a 1/2 second Tv exposure, BYE tells the camera to take the 1/2 second exposure and the camera controls the opening and closing of the shutter.

 

For shooting flat frames you would take a series of pictures while varying the shutter value to shift the image's histogram so that the left-to-right position of the peak of the hump is slightly above the middle. The longer the exposure the brighter the image and the further to the right the histogram peak should be.

 

I hope this helps.

Hi Rick.

Thanks so much, that is a great explanation. It is working fine.

Rich

[trevor@woldsweather.co.uk]

I set AV mode on my Canon 6D Mk2 but EOSBY says TV. How do I set AV in BYEOS?

 

[admin]

AV = you need a lens.

The only option without a lens is you need to select shutter "AV-Flat"