Down sizing photo

[Rocky]

If I just need 8 Mp photos, which method will give me a better picture at the end?
1. Set the 8MP resolution in a 24Mp camera
2. Take the 24 Mp picture and down size with PS later

 

[neuroanatomist]

If I just need 8 Mp photos, which method will give me a better picture at the end?
1. Set the 8MP resolution in a 24Mp camera
2. Take the 24 Mp picture and down size with PS later

IMO, the latter. A bit of sharpening after downsampling helps (I use a light application of PS Smart Sharpen).

The other advantage is if you need more MP later, you have them (assuming you save the 24 MP images, but for that you can use slow/cheap external HDDs).

 

[LDS]

If I just need 8 Mp photos, which method will give me a better picture at the end?
1. Set the 8MP resolution in a 24Mp camera
2. Take the 24 Mp picture and down size with PS later

Number 2.

You'll have far more control of the downsampling procedure, and can tailor it to image content. The camera will downsample the image itself, but with no control over it by you. Unless you need to get the downsampled image as quickly as possible, PhotoShop is the way to go - you could also crop, employ multi-pass downsampling using both the bicubic and bicubic sharper algorithms (although in CC the algorithms should work better when used alone than in older versions), etc.

Or use other tools with different, newer algorithms, i.e. Catmull-Rom - all depends on what kind of quality you need at the new size and resolution.

As Neuroanatomist said, you'll need some final sharpening at the final size - downsampling does clear out sharpening haloes made before. What kind of sharpening to apply depends on your sharpening workflow.