For what it’s worth, I have now found out that if I run ExactScan (downloaded on a trial basis) and use it to scan “using the native scanner”, ScanGear opens instantly and will let me Preview. True, it will not let me Scan - the scanner murmurs and then locks. I suspect that ExactScan does not pass the parameters of a destination file back through the TWAIN interface. Perhaps Thorsten can confirm whether it is the job of the calling application to create the destination file (permanent or temporary), or if the scanner driver creates it and passes it to the calling application?However, that is another problem, which I do not propose to solve as I neither need nor can afford ExactScan.But it does show that a third party application can call ScanGear via TWAIN on my iMac without the Image Capture Extension delay. MP Navigator Ex *might* have got away with it because it is Canon software calling Canon software.John. On 16 Aug 2015, at 10:12, Petur Rasmussen
prasm@internet.is [gcmac] <
gcmac@yahoogroups.com> wrote:I am perfectly able to use twain with the Canon driver. Maybe it uses the special Canon environment set up by Canon on installing the driver.Give it another try.RegardsPetur--------------------------------------------------------Petur Rasmussen e-mail:
prasm@internet.isSa�lheimum 23, 7A Tlf.: +354-553 2858IS-104 Reykjava�k Mobil: +354-822 0645 On 16. a�ga�. 2015, at 08:31, John Hill
john@yclept.wanadoo.co.uk [gcmac] <
gcmac@yahoogroups.com> wrote: I consulted Canon during the Yos 2 research into the problem, and they state categorically that they use TWAIN and nothing else to interface their MP Navigator EX software with my printer.Providing I leave Image Capture Extension running, I can use Image Capture with the scanner, but the images are of poorer quality (at least for my purposes) than those obtained with the Canon drivers.It remains to be seen what happens when El Capitan is released, but I imagine they will update the MD5150 drivers. I don’t think it is in their current catalogue, but it is too recent to become obsolescent yet.John.On 15 Aug 2015, at 19:01, Thorsten Lemke
lemke@lemkesoft.de [gcmac] <
gcmac@yahoogroups.com> wrote:Hello,maybe they use now image capture? Did you try?ThorstenCanon has issued new drivers compatible with Yosemite.
I timed the delay with a stopwatch; it came to 2 minutes 12.9 seconds.Canon’s MP Navigator EX, which also uses TWAIN to call Scangear, has worked perfectly throughout. No delay at all.I checked Activity Monitor, which showed almost identical behaviour to that in Yos 2 - both Graphic Converter and Image Capture Extension “Not responding”, but whereas in Yos 2 I was seeing some 3000 idle wakeups per whatever, this time there was no such frenetic activity.The cure appears to be the same as in Yos 2 - use Activity Monitor to Quit Image Capture Extension. Scangear then opens at once when requested by GC. MP Navigator Ex is unaffected by this drastic surgery, but of course Image Capture becomes useless until I Restart. Fortunately I don’t use Image Capture.I remain of the opinion that there is there is some field in the GC/TWAIN interface which GC is either not setting or is setting imperfectly but which MP Navigator EX gets right. But I do not have the tools, skills or time to acquire either so that I can check (if indeed this is possible).But don’t worry, Thorsten, I know your opinion of TWAIN and I am not expecting you to revisit the interface 
It will be interesting to see what happens when El Capitain comes out...John.