pdxbenedetti wrote in post #18073495
Maybe you need to try reading the whole comment instead of picking and choosing small portions of it which suit your arguments. I said EXACTLY:
I am reading the entire comment. I am simply quoting the parts in question for two reasons. One is to keep you focused on the issue and not allow you to go on a dissertation tangent and getting off the point. Second is because you can't make an erroneous sentence and expect to maintain your credibility. You can't say one thing and then contradict it in the next sentence. That is not how the English language works. Your case is exceptionally special because you are so good with your photography: aspiring astro photogs see your work and then read what you write as gospel due to your talents behind the camera and then you confuse the crap out of them when you contradict yourself.
Lets start with the original problem:
pdxbenedetti wrote in post #18072155
No, not true. Trailing depends ENTIRELY on exposure length, not focal length.
This is statement is 100% inaccurate and you not only know it, you have written other statements saying the opposite. Star trailing is due to both focal length and exposure length. if you shoot a portion of the sky with both a 300mm lens and a 16mm lens for a given exposure length, the 300mm image will see light across more pixels on the sensor for a given exposure length. Even if you are tracking with 99% accuracy, the 1% tracking error will show up in the 300mm image first. TCambel above wrote a great explanation of why above.
Now lets talk about the contradictions is the same paragraph from the post above:
pdxbenedetti wrote in post #18073495
"Again, the rules that people use to determine exposure length are dependent on what they feel are reasonable amounts of star trailing and are dependent on focal length.
Here you say that star trailing is dependent on focal length. this is not what you said above. You specifically went out of your way to say trailing is not dependent on focal length in the quote above.
pdxbenedetti wrote in post #18073495
Wider focal lengths do not mean more or less star trailing,
Hold on now you are saying that wider focal lengths do not mean more trailing which is the exact opposite of saying:
pdxbenedetti wrote in post #18073495
"Again, the rules that people use to determine exposure length are dependent on what they feel are reasonable amounts of star trailing and are dependent on focal length.
pdxbenedetti wrote in post #18073495
wider focal lengths mean you can take longer exposures before that significant star trailing becomes apparent.
Now you are back to saying you can take longer exposures with a wider lens which means focal length is again a dependent factor in star trailing. The amazing thing is that here you contradicted yourself in the same sentence. This blows my mind that you wont recognize this.
pdxbenedetti wrote in post #18073495
Exposure length dictates star trailing, but exposure length is not the only factor for collecting light and collecting light is the most important thing for producing astrophotography images."
This is you going on a tangent. Nobody is saying otherwise.
pdxbenedetti wrote in post #18073495
NOWHERE in this entire statement is a contradiction.
Umm actually... yes there is.
pdxbenedetti wrote in post #18073495
Wider focal lengths mean you can take longer exposures before star trailing becomes apparent.
Wait a minute, so what you are saying here is the exact opposite of what you said here: (Star trailing is dependent on focal length too)
pdxbenedetti wrote in post #18073495
"Again, the rules that people use to determine exposure length are dependent on what they feel are reasonable amounts of star trailing and are dependent on focal length.
pdxbenedetti wrote in post #18073495
Exposure length dictates star trailing.
This is only half of the truth. Focal length also plays into it. Define the 500 rule as you know it and feel free to substitute any other number you want. I am guessing you would word it something like this:
500 Divided By the Focal Length of Your Lens = The Longest Exposure (in Seconds) Before Stars Start to “Trail”
If focal length didn't play into it, why is it in the equation?
pdxbenedetti wrote in post #18073495
So in VERY SIMPLE $%*(ing terms: Exposure length (which dictates how much star trailing ACTUALLY OCCURS) is calculated in various forms using various equations based upon what people can accept in terms of star trailing, that exposure length they calculate will then produce an image with X amount of star trailing.
See the 500 rule bolded underlined in red above. See how there is a focal length in the equation? You are missing half the equation when you made the above comment.
pdxbenedetti wrote in post #18073495
Exposure length ENTIRELY dictates how much star trailing occurs in an image.
No both focal length and exposure length dictate together how much star trailing occurs in an image.