Lightroom images do not look the same when opened in PSCS5

Question

Hi,
I am using LR 3 and PS CS5, but have an annoying problem which I don't know how to fix. Basically, when I look at an image fit in window inside LR 3, it looks real well as far as contrast and saturation and hue... when I choose  Edit In Photoshop CS5, the file opens in PS but the contrast and saturation and even hue are slightly off. Why?
Thanks,
Juan

Answer 1

Juan, note that in Develop Lightroom does not use all of the available raw data at once to give you a preview. It does this as otherwise, the program would be unusably slow. Every move of a slider would have to result in a complete rerendering of the data at full resolution and then downscale the image to screen resolution. Even on the very fastest machines out there this still takes about a second which would make everything glacial especially on normal computers. So in zoomed out views, it simply takes a subset of the raw data at lower resolution and uses that to render. This can subtly affect saturation in cases where there is a lot of fine color detail because there is no averaging going on to arrive at the lower res image. When you zoom in to 1:1, Lightroom simply renders only the small subset of the image that you see in your window. Because this is only a small subset, this is again very fast, but is now done at the full resolution. In Develop, you will only in 1:1 see Lightroom apply noise reduction and sharpening which can also affect apparent saturation at zoomed out levels. This will certainly remain an issue until we are a few generations further on Moore's curve. However at that point the resolution of cameras will have increased by the exact same amount making the problem remain.
Now consider what happens when you go to Photoshop. Lightroom (or ACR when you use "edit in Photoshop") renders the image from the raw into usually a 16-bit prophotoRGB tiff. This is then opened in Photoshop. Photoshop does NOT know how to deal with raw data. It needs a fully rendered RGB image which is supplied either by ACR or Lightroom. Now, since you have a fully rendered image, scaling down is very easy. However, you no longer have the freedom to reinterpret the raw data. The model used in Photoshop is very different from Lightroom and therefore different restrictions apply.
In Lightroom's Library views, a prerendered jpeg is used for the display. This means that in Library view, the image is scaled down from a fully rendered image and should show a desaturation with respect to Develop when you have lots of fine color detail. Note that neither Lightroom's Library preview and Photoshop's scaled down preview are actually accurate. Both scale in a gamma corrected space, but only for display. To compound this, Lightroom scales down using a different algorithm than Photoshop (which uses several mechanisms based on the zoom level - i.e. whether it is divisible by two).  It is simply impossible to highly accurately display a high resolution image on a very low resolution computer display. You always have to deal with scaling, for which there exists no most correct method. They all have issues (certainly Photoshop's silly method does).
Lastly, many people that see subtle (or even extreme) differences between Photoshop and Lightroom actually have a problem with their monitor profile. Make sure to recalibrate your monitor and when you do, make sure that the calibration software generates a v2 profile (most profiling software has this option in the advanced setup). Lightroom treats v4 LUT monitor profiles differently than Photoshop. This difference will be gone in a v2 matrix profile.