TIFF File Exposure is way off from selected settings

[angelo327]

I'm having an issue with the resulting exposure of .TIF files.
In Settings, Image Capture i'm selecting Quality RAW and checking the box "Create TIFF image file".

The link below is to my OneDrive share and includes 4 files.
No Username or Password is required; anyone with the following link has view access:
https://1drv.ms/f/s!AiBp0L32JqxNmBNkWHNbzp0n3-cp

The first three are as saved by BYN:  exposure time for all three are 1/30th sec at ISO 3200.  The target is inside my house and well lit by two 75w room lights.
D90_3200_Tv130_20240210-13h46m30s232ms.NEF   All .NEF files are well exposed using the 1/30sec at ISO 3200.
D90_3200_Tv130_20240210-13h46m30s232ms.NEF.EXIF
D90_3200_Tv130_20240210-13h46m30s232ms.tiff    All .TIFF files appear totally dark.  Any viewer I use to open one shows a totally black image.

After pulling the .TIFF file into Adobe Lightroom and stretching it by 5 f-stops plus enhancing brightness I see there actually is an image. 
I exported the stretched image from Lightroom and saved it to my OneDrive as D90walltarget_Hi-0.3_Tv12_20240210-16h32m50s437ms.jpg   

This has been happening for some time and i'm anoid that I didn't figure this out sooner. 
My question is why is there such a huge difference in exposure between the RAW or RAW+JPG files and a .TIFF file?

 

 

 

 

[astroman133]

Raw NEF files are mostly unprocessed linear images. They may be stretched for display purposes, but this does not affect the original data. TIFF files are created from the linear RAW images and so are also linear and unstretched.

Astrophotography images that are only 1/30th of a second exposures will be very dark. Remember that when you stretch them, they will be brightened, but that process will also brighten the thermal noise in the images. This is the nature of astrophotography. It is why you need to stack multiple long exposure images to reduce random noise and provide the ability to bring out the dim details while suppressing the noise.

That said, I never use the TIFF conversion that is provided by BYE or BYN. My processing workflow converted the debayered RAW images to FITS. I worked with the FITS files and then created a non-linearly stretched JPG file at the end.

[s3igell]

The "Brighter Exposure" that you are used to from programs like Adobe Lightroom or even Windows Explorer are the product of a "Default Conversion" done by those softwares before displaying the Image on the screen.  That is done because they know the Intended Use is Display to a Human rather than Astro-Image Processing.  That "Default Conversion" includes applying a Stretch and Gamma Curve as well as significant amount of Color and Saturation.  All of this is needed so that an Image captured by a Camera can match the expectations of what a Human sees of the Real World with their Eyes.

On the other hand, all of those Image Processes are detrimental to the data that is required to do Astro Image Calibration and Stacking and Post Processing.  Since it is this process that you intend for the Images that you captured, BYN would be doing a disservice (actually Damaging) the Images if it did any of the "Human View Oriented Processing".  Instead, it leaves the data as a "RAW TIFF", so that you can directly import into the AP-Imaging Software of your choice.

[angelo327]

Thank you for the explanation.  I have been aware that Lightroom has a default enhancement applied to my images and frankly it anoyes me; but I didn't realize how that process was performing a neccessary disservice.