FIltering of an image

Hello, Please can you suggest any filters in which I can highlight the sides (in red) of this bubble?

Thanks in advance.

[Image Analyst]

No. Why is that tiny speck of white inside the red oval any different than the hundreds of others. This image would be almost impossible to accurately gauge bubble size. I suggest you pick a different metric to characterize your fluid, like mean gray level or something. Maybe mean gray level is correlated with the number of bubbles in the fluid which is then correlatable to something else, like the compressibility of the foam or something like that.

[Jórdan Venâncio Leite]

Thanks for your answer imageAnalyst. I really thought it wouldn't be possible to calculate it too

[yanqi liu]

yes，sir，In human eye，what is the rule to judge this target？

may be it is a moving object？

[Jórdan Venâncio Leite]

The objective is to measure the size of the bubble. Thanks for your answer!

[Jórdan Venâncio Leite]

Image Analyst, do you think I could calculate the bubble size using the mean gray level as you said above? I need to highlight through the filters at least half of this image (the half of the bubble outline - the left side which I find easiest to filter) (it's in the picture below) as it is in the red circle.

[Jórdan Venâncio Leite]

Thanks in advance!!

[Jórdan Venâncio Leite]

Please answer bellow Image Analyst, so i can choose it as the aswer for the question.