iphoto won't open with after installing yosemite 10.10.3

Effective with 10.10.3, you should begin using Apple's new Photos app. When you launch it for the first time, follow the on-screen directions. There will be a learning curve because it is a new app. If you need support for Photos click Photos for Mac for assistance.

Although Apple has released the new Photos application with 10.10.3, you should be able to continue running iPhoto if you have/get version 9.6.1. You should be able to get it through the Purchases tab of the Mac App Store application after moving the pre-9.6.1 version from the Applications folder to the trash.

markwmsn wrote:

Although Apple has released the new Photos application with 10.10.3, you should be able to continue running iPhoto if you have/get version 9.6.1. You should be able to get it through the Purchases tab of the Mac App Store application after moving the pre-9.6.1 version from the Applications folder to the trash.

It is almost always wiser to move forward rather than try and stay with a current product. While technically you are correct, are you really providing the OP any help by suggesting he stay with a soon to be antiquated product?

rkaufmann87:

Given that Photos 1.0 is severely lacking in features compared to the mature (and aging) iPhoto 9.6.1, some users may reasonably choose to defer switching to Photos. IVANfromcanada expressed a desire to know how to run iPhoto; I provided the information. Maybe I should have explained further.

IVANfromcanada: rfaufmann87 does have a point. You should plan to transition away from iPhoto at some point, as Apple has indicated that it will no longer be updating iPhoto or Aperture. Apple's path lies with the new Photos application, it seems. You should try it out, then decide if you want to switch to it now, wait until it is more mature, or switch to another product like Adobe Photoshop Lightroom.

markwmsn wrote:

rkaufmann87:

Given that Photos 1.0 is severely lacking in features compared to the mature (and aging) iPhoto 9.6.1, some users may reasonably choose to defer switching to Photos. IVANfromcanada expressed a desire to know how to run iPhoto; I provided the information. Maybe I should have explained further.

IVANfromcanada: rfaufmann87 does have a point. You should plan to transition away from iPhoto at some point, as Apple has indicated that it will no longer be updating iPhoto or Aperture. Apple's path lies with the new Photos application, it seems. You should try it out, then decide if you want to switch to it now, wait until it is more mature, or switch to another product like Adobe Photoshop Lightroom.

Purchasing Adobe LightRoom as an upgrade from iPhoto is an alternative however remember Lightroom is intended for professionals and is difficult to learn. Also remember Photos as you stated is a 1.0 product, which means it is VERY early in it's development and almost certainly have additional features that iPhoto and Aperture had. For most end users, Photos is a nice little product. I was using Aperture (overkill for my use but I was used to it) and converted to Photos. While it doesn't have everything I want, I am sure it eventually will. Frankly I did use LR and found it very difficult to use and did not like the work flow at all.