iOS 7.0 and up: Image size for 3.5 retina iPhone

I'm doing walkthrough module and have issues with showing custom images in an imageView while sliding.

I have prepared images for for iPhone 5+ and special sized set for iPhone4.

5 and 6 - image@2x = 640 x 1136
6+      - image@3x = 1242 x 2208
4       - image3_5@2x = 640 x 960

It works flawless in 5,6 and 6++, but not on iPhone4 image looks blur and doesn't fit.

I store images in Images.xcassets folder.

for 5 and up

for 4

What's wrong with it? Thank you in advance.