Open raw vs Open jpeg as raw

[glenna1984]

What is the difference between opening a raw file in PS CS5 vs. opening a jpg AS RAW?

Does any of this work in LR 3?

Thanks,
Glenn

 

[Steve]

You're not actually opening the JPG as a Raw file, your just opening the JPG file in the Adobe Camera Raw converter (ACR).
A JPG has all the image settings locked in.
Even so, opening the JPG in ACR gives you some ability to adjust things like white balance, contrast, exposure, etc.

A RAW image is really the Raw data file created by the camera.
It has a larger dynamic range so you can compensate for a under or over exposed image within limits.
Adjustments like white balance, contrast, saturation, etc., are completely adjustable and not locked in like a JPG.

I think the biggest advantage to opening a JPG in ACR is adjusting for blown out highlights.
You can't bring back what isn't there but can minimize the problem in some images.

 

[glenna1984]

Thanks for the explanation. It clarifies a lot.

However, it does open the door to one other question about the above.

If I open a jpeg in ACR I seem to see the same options and sliders as I do if I open a raw file. Am I to assume I am not getting as much range of control with the former?

 

[Steve]

If I open a jpeg in ACR I seem to see the same options and sliders as I do if I open a raw file.

That's exactly right you get the same screens and sliders but not all the sliders will work the same.

For example Temperature and Tint are just plus and minus sliders because the white balance settings is already baked into the JPG and your pull down options are only As Shot, Auto, and Custom.

With a Raw file you can set the temperature to a specific color temperature or white point setting.

If the camera was set to tungsten and you were shooting in bright sunlight a JPG would be very difficult to fix.

If it was taken in a Raw format you just change the white balance setting in ACR to Daylight (5500°K) or use the slider to move the temperature up or down until it looks right to you.

Am I to assume I am not getting as much range of control with the former?

That right, RAW files have a larger dynamic range.