I have an issue on the memory warning

hello everyone
i have problem with my app i have create app photo lock please i have problem when i load all images from photo library in my collection view when i reduce the size of image the image display low resolution and the image not clear like photo in camera and when i increase the size image using PHImageManagaerMaximumSize i have received memory warning please any idea for increase image size for increase resolution photo like photo library in iPhone

and this is my code below

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) → UICollectionViewCell {
let cell = myCollectionView.dequeueReusableCellWithReuseIdentifier(“Cell”, forIndexPath: indexPath) as! SelectImagesCollectionViewCell

        let asset = photoAsset[indexPath.row] as! PHAsset
    PHImageManager.defaultManager().requestImageForAsset(asset, targetSize: CGSize(width:350,height:350), contentMode: .AspectFit, options: nil) { (img:UIImage?, obj:[NSObject:AnyObject]?) in
            cell.imageViewCell.image =  img
    return cell

How many images are you loading into cells?

Isn’t 350x350 a lot larger than you would need to display in a cell?

all images from photo library depending on the phone picture this app photo vault i know 350 * 350 is high quality but when i reduce to 105 * 105 the image work fine but the image not quality(not clear) if i put 350 * 350 the photo is quality but display to me the memory warning is have another way how can i get the images without memory warning

thank you