Very large file.

Kesswicklimey

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I am new to using photoshop in conjunction with Lightroom.
I recently took three images into photoshop to process as I had focus stacked the shots. The file that comes back to Lightroom is a TIFF which I assume is the norm. However what stunned me was the size of the file. The three DNG files were around 36MB each yet the Tiff that came back is 1.02GB, is this normal or have I done something wrong that has resulted is such a large file.
 

Ferguson

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Short answer: Yes.

Somewhat longer answer: It depends a lot on what you do, as well as what options you use on the save. Generally people use TIFF to keep from having data loss due to (for example) JPG lossful compression, and they use 16 bits. That's a good thing, but it adds to the space substantially.

Layers add greatly to the space. But generally if you plan further editing and you use layers, you need the layers preserved. But if not, you can "flatten image" and save a lot of space -- it does a not-reversible merge of the layers into one.

Also, lossless compression is possible - when you save, there are various compression and legacy options, generally speaking use the best (it indicates mostly, but generally zip for both options) is smaller, but some compression and compatibility options are incompatible with other programs including lightroom. You may want to experiment, and also decide to what extent you want lightroom to view/edit the image itself, as opposed to always doing an "edit in photoshop" from lightroom.

But... TIFF's are big.
 

LouieSherwin

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Another important distinction is difference in how the color information is stored in a raw file as compared to a TIFF or PSD file. In a raw file each image pixel is stored as a one or two bytes ( 8 bits or up to 14 bits depending on the camera) and the color ( red, green or blue) is determined by the position in the sensor by the color filter array.

Raw data has to be converted to RGB data before Lightroom or Photoshop can be used to edit the data. This process is called demosaicing. This happens dynamically inside of Lightroom so you never resulting file but it creates a RGB image that now has three numbers one each for red, green and blue for each pixel. Internally to Lightroom this is a 16bit RGB this means that there are 2 bytes for each color for a total of 6 bytes for each pixel. So if your raw capture is 8 bits (1 byte) per pixel then the internal file is now 6 times larger. As I said you don't actually see this but it does factor into the need for a lot of RAM to handle processing images.

When you export to Photoshop you have two options, either 8 bit or 16 bit. Using either option is going to create a much larger (3 or 6 times) TIFF or PSD file.

-louie
 
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