Enhance will applies the changes most likely to improve the photograph.
Rotate rotates the image in 90-degree increments.
You'll find eight filters in Filters: Mono, Tonal, Noir, Fade, Chrome, Process, Transfer, and Instant.
With Retouch you will be able to remove spots and blemishes, as well as Crop and Adjust. Crop features a wheel similar to the one in Photos for iOS. This wheal includes a tool for straightening the image (as well as an Auto button that will straighten the image automatically, according to the horizon). You can also choose the aspect ratio for your crop, as in iOS Photos.
The adjustments available in Photos for Mac are also similar to those in Photos for iOS. Adjustment options include Light, Colour and Black & White and these are controlled via smart sliders. For example, if your image is too dark you can click on the Light tool and drag the slider to the right to lighten the image. The changes are much more in-depth than many will realize, Apple isn't simply changing the light levels, but also exposure, highlights, shadows, brightness, contrast, and black point. Photos calculates the best look for the overall image. This simplifies the way you edit photos, but maintains fine-tuning behind the scenes.
If you are thinking that this means you can no longer fine-tune images as you used to, you are wrong. Just click on the downward pointing triangle next to each control to see a series of other controls including Exposure, Highlights, Shadows, Brightness, Contrast, and Black Point. You can tweak until you are happy with your image.
There are even more editing options available if you click on the Add button in the edit area. Here you will find Histogram, Sharpen, Definition, Noise Reduction, Vignette, White Balance, and Levels.
When you edit images this way you aren't actually changing the original image in any way, images are stored in their original format and resolution - including raw images. The Photos app just shows that image with your changes applied.
You can find more detail about using Photos for Mac below.
Photos for Mac OS X and iCloud Photo Library
The key advantage of Photos will be its close integration with iCloud, and in particular Apple's new iCloud Photo Library service.
iCloud Photo Library is currently in beta form on iOS devices (you can find it under Settings > iCloud Photos). It will store all the photos and movies taken on all your iOS devices, and eventually any images you import to your Mac, on Apple's iCloud servers. You will then be able to view your iCloud Photo Library on all your devices.
You will likely need to add more iCloud storage if you want to be able to view all your photos on all of your devices. You can read more about iCloud here. The iCloud pricing options are as follows:
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