BirdForum is the net's largest birding community dedicated to wild birds and birding, and is absolutely FREE!

Register for an account to take part in lively discussions in the forum, post your pictures in the gallery and more.

Reply to thread

Message: <blockquote data-quote="typo" data-source="post: 3143572" data-attributes="member: 83808">Analysing and designing out observer bias has been a significant part of my professional life and I quite understand the point you are making. I'm probably more aware of the dangers than some but it's almost impossible to avoid it completely without 'blinding' the study. Unfortunately I don't think it's practical to go to the lengths you suggest, particularly at two remote sites. What I would normally do for my own tests is simply randomly change the distance between observations so I couldn't predict a result, but I recently discovered a complication. I had been using anything between 7m and 30m and had a feeling that I was getting better results at longer range but the differences were small. Recently a forum member was kind enough to donate a better chart  which allowed me to get down to 2.5m, (which would be great for indoor testing) and it became totally obvious that I was getting poorer resolution results at near focus than longer range with a new acquisition. I was waiting for better weather to retest all my roof binos to see if the phenomenon is more widespread. I'll stick with 10m+ for this comparison.David</blockquote>