Adobe Camera Raw (ACR) - a quick tutorial

[eccles]

This is my method for using Adobe Camera Raw (ACR) as supplied with Photoshop CS3, currently ACR 4.6
One of my favourite butterfly lenses is a 20 year old Minolta zoom often called a 'beercan' because of its size and shape. It is very sharp with very good colours and bokeh but suffers a little with red/green chromatic aberration when at full zoom. Using the camera's raw option allows me to correct this within ACR.

After uploading your images from your camera to PC, proceed as follows.

Start Photoshop.

Select menu File/Open.

Navigate to where your raw files are stored and select one.

Adobe Camera Raw (ACR) will open your raw file and display it.
You may need to wait a few seconds for the "!" to disappear denoting the file has fully loaded.

With the panel on the right set to 'Basic', which is the left most symbol that looks like an aperture diaphragm you can set things like white balance, exposure correction, black depth, recovery for burned highlights etc. The fill light can be useful to bring out shadow detail, but be careful not to overdo it.

You can also play around with levels with the next tool along on the RH Panel called 'Tone curve', but mostly I don't bother with it.

Use the magnify tool (top left of ACR screen) then use cursor select to find a section of the picture near an edge where there is some detail. Ensure the selected portion is magnified to least 100% - anything less will not show changes made in the next step. You can use the -/+ controls bottom left to change magnification.

Select Lens corrections from the right hand panel - third symbol from right.
While holding down the 'alt' key use the sliders to correct any RG or BY chromatic aberration. My beercan lens is sharp but has a bit of this that needs correction. Any purple fringing at contrast edges can also be minimised by selecting one of the defringe options. If you have a wide angle shot there may be some vignetting, which can also be corrected with the vignetting tool.

Still at 100% or greater, select the Detail option from the right hand panel (third from left)

Use the panning tool (hand symbol, top left) to select a smooth, dark area to check for noise.
Adjust noise parameters as you think fit. It will depend on your camera model and also the iso setting of your camera. For instance for iso800 I find I can use about 10 for the luminance and colour sliders with masking set to 5 with little visible loss of detail, but it all depends on how accurately the exposure is. For iso400 I need less than this, often none at all. You can leave a small amount of 'grain' because unless printing a very substantial crop it isn't usually noticeable in a print. You can also adjust sharpening here too. I find you can go up to at least 50% with around 0.5- 1 pixel radius without any significant loss of fine detail whilst enhancing the detail you have. If I'm going to resize later for web display though I don't sharpen here but leave it to the resized jpeg.

Use the size drop down tool (bottom left) to select 'fit in view'

Use the crop tool (fifth symbol from left at top of ACR screen) to frame image.

For me, that's about it. Select Open Image (bottom right) and you're then working with normal Photoshop mode.

One thing to note is the colour standard that you use that is dsplayed along the bottom of the ACR screen. You can click on this to change the default but it should be the same as that set by your camera. It'll usually be sRGB but your camera may use Adobe RGB instead. If I want to print my image I select sRGB 16 bit as this uses the full 12 bit per colour range (36 bit total) of the camera. Jpeg only supports 8 bit per colour so the resultant image from a 16 bit raw option cannot be saved as jpeg. I save the image as 16 bit tiff as my printer software can handle that directly.

[Shirley Roulston]

Thank you Eccles for taking the time to type all that out, I'm going to print it out and keep it, the best instuctions that I've seen, better than any photo magazine. Many thanks. Regards Shirley

[Malcolm Farrow]

Hi Shirley

I'd only add that while shooting RAW adds an extra step it's well worth the trouble and, occasionally, I've been able to save images that might otherwise have been completely lost. Depending on your equipment, how the camera is set up and how you shoot, you may not need to do much to your pictures once they're loaded in ACR but, as Eccles has explained so well here, if you need to do any adjustment, you have all the tools you need. It's so much better than shooting JPEG where any subsequent manipulation is likely to have a detrimental impact on the quality of your image. And with a little practice it will become second nature.

Good luck and best wishes

Malcolm