The Sony a1 is their first model to embed a full sized preview in the raw files. All previous Sony models only has the 1616 pixel embedded preview. Most Sony shooters set their cameras to shoot raw + jpeg. Photo Mechanic will pair up the files by default using the jpeg for the thumbnails and large previews, making it easy to check for sharpness.
Another option to see a full sized preview would be to convert the ARW files to DNG files. You will need to have one of Adobe's DNG Converter apps installed before you can create DNG files in Photo Mechanic. Once the DNG Converter has been installed, go to the Tools menu to access the Convert RAW to DNG utility. Click the Pick DNG Converter button to set the path to the Adobe DNG Converter application.
The Render Cache preferences can be enabled to generate full sized previews for your raw files. This utility also requires a DNG Converter app to be installed. Set the path to the DNG Converter on the Render Cache preference page. Many users do not like this option do to the slow performance generating the cached previews.
Best regards,
--Bob