I hear exactly what you are saying!!! ha ha....
I hate seeing the pics on the back of my camera, and on the screen, they look great, but when I upload, a big NO happens!
I was recently discussing this with a friend. Digital cameras have come a long way. Now, they are so much cheaper than what they used to be.
From what I have experienced, I get the best pics when:
The snake is not moving.
I am not moving.
Lately, my better pics have been outside with no flash.
To me, for pics to be good, it is half the camera, half the photographer. I have taken such horrible pics, and I still have pics come out blurry, etc. but I have also noticed characteristics about lighting, movement, etc., and how they can all play a part in how your pics come out.
I have used flash indoors with great results. Lately, though, I have done most of my pics outside with no flash, and the colors on the snake seem more " real " to life than with the flash.
The only thing I can recommend is just trial and error, and restrict the movement of yourself and the snake to nothing, if possible. Experiment with taking pics with flash, and then take some without, and see what differences you can tell.
Here is a recent pic of my snow Southern pine. I don't have any recent pics of my albino Nelson milk, so I thought I would use this as an example. Pretty decent pic, but also, you gotta take a whole slew of pics right then and there and then pic out the best ones later.
I use a simple and older digital camera, a Kodak DX3700 3.1 megapixel. It was around $249.00 when we bought it back in 2001 but now it probably $99.00 or below.

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Genesis 1:1