Performance degradation in folders with thousands of files

[vhugoalv]

Using convert method from shell or COM+ object in folders with 32000 files takes 12 seconds to perform in one file.
Moving the same file to an empty folder and using the same code, takes 1 second to perform.
What can be the issue?

Code:
C:\PROGRAM FILES (X86)\ImageMagick-6.9.1-Q16\convert "\largefolder\file.bmp" -resize 525x525 -gravity center -background white -extent 525x740 "C:\TEMP\{CB36BF73-6C57-11E7-982E-78E7D1CA402C}.bmp.jpg"

[vhugoalv]

It occurs in last version too.

[snibgo]

IM simply asks the operating system to open files. If that takes a long time in directories with many files, the same problem would occur with other programs.

What version of Windows? What is the filing system? Old versions of these gave bad performance when directories contained many files.