on landscape The online magazine for landscape photographers

Turbocharge your Photoshop

Speed-up the processing of large files in Photoshop

Skip to Comments
Tim Parkin

Tim Parkin

Amateur Photographer who plays with big cameras and film when in between digital photographs.

Flickr, Facebook, Twitter

Now with all of these high megapixel cameras coming out, one of the clarion calls of the naysayers is that "we'll need more powerful computers and more storage" - well the more storage is a red-herring unless you really are heavy on the shutter release. However, it's true that 40+ megapixel images can be a pain, especially if you have many layers in your files. And once you do have quite a few layers, you can get close to the 2Gb Photoshop file limit quite quickly.

Now it's bad enough that it slows you down but this also gets in the way of your creativity and so anything that can give you a performance boost without spending a lot of money can help you produce better images. Now I'm probably a special case but when I scan my best 4x5 images in, I do so at 4000dpi and end up with a 1.8Gb file. These files were becoming a pain to edit - making a cup of coffee whilst you wait for a Gaussian Blur to finish gets tiring very quickly.

A couple of months ago I decided to do something about this and purchased 16Gb of RAM for my Mac Pro and I also bought two 80Gb SSD hard drives with a RAID card that combined the two into a single very fast scratch drive for Photoshop. Although this did improve the performance quite a lot, things were still slow enough to be a pain.

So I ended up looking at a technique I had used a couple of years ago when I was doing most of my work on a laptop. Most of the changes I was applying to my images were quite broad in terms of dodging and burning with large radius brushes or applying global corrections. I tried an experiment and reduced my master scan by 25% and then worked on it as I normally would. Obviously the performance helped massively. The trick now that I had finished doing my edits was to resize the image by 4x, open the original scan and replace the bottom layer in my Photoshop file with the original 4000dpi scan.

Hey Presto! hi-res file ready for printing! I could flatten this now and sharpen or apply noise reduction and print as needed.

Obviously this does have a few restrictions though. You can't make any changes that affect things on the pixel level, so no noise reduction, sharpening, high pass etc. and, of course, the changes you make have to be kept in layers.

Keeping your edits in layers is a very good habit to get into anyway as this means you can always back track and make changes if a layer is causing issues - non-destructive editing at it's best. However, there are a couple of tools that rely on a flat layer in order to work and that, obviously, cannot be used in this way. The most useful of these is the Shadow/Highlight tool and I spent a few hours trying to find a way to similar this tool just using curves and masks.

How Much Space do Layers Take Up?

Well this is a little tricky to answer because it depends on what is in the layer but there are some general guidelines for you. Firstly, a layered tiff file will almost always take up more space than the equivalent layered Photoshop psd file. When you add an adjustment layer to a Photoshop psd file, the size of the file saved to disk will not go up more than a few kilobytes - this is because Photoshop psd files have extra information in them that can identity a layer mask as being empty. However a tif file does not have this ability and so stores the empty mask layer as a full size, mono file. This means that an adjustment layer can take up an extra 30% of the image size even if it has no mask (the mask is stored as an extra image at the same bit depth but as a mono/b&w file).

If you use a lot of non-masked adjustment layer, this can add up to quite a bit. So, in short I would recommend that you always save your images as psd files rather than tiff files and you don't need to worry about removing those empty masks that end up associated with each layer.

As a side point, if you have a very big file without adjustment layers and you want to save as much space as possible, make sure you have fully flattened it to a background layer as a photoshop file that contains just a single layer with no background takes up significantly more disk space than a photoshop file with just a background layer. Oh - and one more side point. An LZW compressed tiff (one of the options when you save a tiff) will be smaller than the equivalent psd file. However, if you want to be really anal about saving disk space (and it probably isn't worth the bother with disk prices dropping as they do) then a zipped psd file is smaller still than an LZW compressed tiff file.


Non-Destructive Shadow/Highlight

NB: As pointed out by a reader - there is a non-destructive shadow highlight already but it relies on converting the image into a smart object. The problem with this is that you then cannot replace the bottom layer (as far as I know). If you want a similar effect that the shadow highlight produces, the following is a brief explanation of how this works. In a following article about luminosity masks, I go into more detail including a video.

Now most of the adjustments I make using shadow/highlight are to lift the shadows and even if I have to reduce the highlights, I tend to do this with a global curves brightness reduction and then use shadow/highlight to lift the remainder of the picture.

The central part of this technique relies on creating a rough mask that only allows the shadows to be accessed. In order to do this, we need to use luminosity masks - a subject we will cover in our next issue.

However, to summarise, you create a luminosity mask (go to Channels panel, click on 'make selection from channel' or press the dotted circle button at the bottom of the panel. This makes a selection based on the brightness of the image - 100% selection where the image is white and 0% selected where the image is black.

If you now add an adjustment layer, the adjustment will be masked by the selection. Once this is done, the clever bit is to blur this selection by a very large value. For most DSLRs blurring by 250px does the job quite well. How do you blur the mask? Well as long as the mask is selected - i.e. it has lines around it - then when you apply a blur, it only applies it to the mask.

Finally, you want to tweak the contrast of this mask because it will be looking mostly grey - to do this you should 'alt-click' or 'option-click' the mask which will show you the mask itself as a black and white image. You can now use curves or levels to make sure this mask has values from black to white to ensure that the masking effect works well. Now alt/option click to get back to your normal picture.

Finally, just add a brightness boost using the adjustment layer and it should only brighten the overall darkest areas. A video will be added here on Monday to show the process.

Next issue will go into detail about the luminosity masks, a very powerful feature that is especially useful when you want to use a non-destructive process.


  • Hi Tim,
    That is a great tip and for anyone who want to see how it’s done then there’s an in-depth tutorial on this here http://www.westcoastimaging.com/wci/page/info/photoshoptip/podcast_guidefile.html

    • Typical – there are no new ideas.. :-)

  • I’ve been using the ‘west coast’ method for a few years now – sorry Tim. You lost me on the last section though, I’ll wait for the video.

    • No problem – Video coming this evening.

  • drknight

    Hi Tim – I’m learning a lot from these tips and tutorials, and it would be really useful to be able to access them as a series. Maybe you could put together a set of links to all of these articles, or more generally sets of links to themed articles from past issues? Dave

  • About 1 million Internet Years ago there was a Photoshop competitor acquired by Macromedia, called xRes ….

    It sort of did this sort of thing straight out of the box. But even then (1997?) there was no competing with The Almighty.

  • Seamuscamp

    “However, there are a couple of tools that rely on a flat layer in order to work and that, obviously, cannot be used in this way. The most useful of these is the Shadow/Highlight tool”

    The S/H tool can indeed be applied non-destructively (certainly in the latest Photoshop version) albeit not via an orthodox adjustment layer. The key is the “Convert for smart filters” option in the Photoshop Filters menu which (amongst other things) names your background layer 0. This function means that when you use S/H, you generate a layer mask which appears below layer 0 in the layers stack. Double-click on the adjustment name and the S/H dialog comes up with your original settings which can be adjusted.

    I think this technique is broadly comparable to adjustment layers and can be used for all those pixel-level adjustments that can’t have adjustment layers per se. Seamus

    • That is true, however you can’t then replace the bottom layer as far as I understand it. I’ll change the article to explain this.

  • Seamuscamp

    I’m not an expert in Photoshop – far from it; so I’m merely pointing out that your proposed workflow, for most purposes, seems to be re-inventing the wheel. I don’t know when you would want to replace the bottom layer (after all the background layer is the original photograph and is locked). If you want to apply the same settings to a different photo, just use the “Save as Default” button.


    • Can you explain what you mean by “Save as Default” button? Can’t find any reference to it in the manual or in Google…

  • Seamuscamp

    Ah, manuals! The Adobe culture seems to be to give you enough to get started and leave the rest to luck or to the huge support industry that has grown up around Photoshop.

    In the case of S/H, when you first open it, the dialog has two elements – simple shadow and highlight amounts. But tick the “show more options” box and those options expand – plus some further colour & contrast options. In the bottom-left corner is the “Save as defaults” button. There is also the option to “save” a group of settings under a name of your choice.

    Incidentally I came to this page without logging in and was surprised to see one of the Capcha words was Irish for “death”, in old script containing two letters which don’t appear on a laptop keyboard (or in the English alphabet). A good way to keep visitors to a minimum!


  • The issue was to do with non-destructive shadow highlight though? How does this help? i.e. If I get to the sixth adjustment layer and then I want to add a shadow highlight type adjustment and then carry on adding a couple more dodging and burning layers, how would you do that? I’d love to be able to use built in tools in this way (ideally it would be good to use smart objects in the fashion I’m looking at)

    p.s. If you don’t like the captcha word, click the refresh symbol. Interestingly, it only checks one of the words anyway (your translation of the other word is used in attempts to optical character recognition old books for library projects).

    • Seamuscamp

      This issue has wobbled around a good deal from the original concept. For non-destructive s/h, the most effective and most straightforward method is via a smart-object conversion. Normally this should be carried out first – if later then any previous adjustment layer would be compromised. God knows what adding an s/h adjustment would do at the end of a sequence of six adjustment layers. Colin is absolutely correct – smart objects are simple and work transparently and are adjustable.

      Your point about saving space is beyond my experience. Perhaps saving a masked layer amended by a curves adjustment layer takes up a lot less space than a smart adjustment (I don’t think it does) but it certainly uses a lot more time.


      • Hi Seamus – the original concept is to work on a reduced size version of your file to speed up processing. Then when you’ve made all of your changes, you can substitute a full size file at bottom of your adjustment layers. The speed increase is due to not having such a large file at the bottom of the stack.

        e.g. Imaging if you had a 7Gb panorama that you had stitched together. You downsize to a 300Mb file and then make your edits, then you upsize the image and replace the bottom layer.

        Can you explain how you achieve this with smart objects? I’d love to know but can’t get my head around how to do this or even if it is possible?

        • Seamuscamp

          As I said originally, I am no expert on Photoshop. But, in the context you indicate, I think the answer is simple enough.

          1 Make your reduced image a smart object.
          2 Apply your s/h adjustments
          3 Save the smart adjustments under some appropriate name.
          4 Open a copy of the full-scale image as a smart object
          5 Apply the saved smart adjustments
          6 If any fine-tuning necessary, do it.
          7 Save the fine-tuned adjustments (if necessary under a new name)
          8 Flatten the image

          All adjustments are reviewable whether presenting as adjustment layers or smart filters. The general process can be repeated. Nothing is destroyed or lost.

          How glad I am that my image files are of “normal” size.


  • Colin Brookes

    Why not just turn the background layer into a smart object in the first place
    as it can be scaled down and back up without damage, keeping all the adjustment layers.

    What am I missing here, as this is simple and works for me without degrading the original?

    • That does work but the file would remain the same size on disk and in memory – the idea is to reduce the cpu load and memory/disk space.

  • “The problem with this is that you then cannot replace the bottom layer (as far as I know). ”
    Maybe I misunderstood you here, but you can right click a smart object and choose Replace Contents

    • Well you learn something new every day :-) – I’m playing with this and it has it’s issues (the adjustments are not scale independent and when you scale the image and then replace the contents with a larger file, the larger file is scaled as well. I think with some fiddling around this might work, as long as your shadow highlight is on the bottom layer… worth playing with more though – thanks!

      • “Well you learn something new every day” – exactly my thoughts when you pointed out the little circle in the Channels palette. ;) No-one ever knows every dark corner of Photoshop.

        I mainly use Replace Contents with raw files where I’ve re-edited the original raw file (in Lightroom for instance) and then want to update the smart object in the TIF/PSD.

  • I fully sympathise with the problems around editing big files which only get worse as files get bigger so if you upgrade the camera budget for a new computer and storage!

    I must admit to not doing a lot of editing in PS6, just the odd tweak here and there and since I have changed the RAW conversion software I am making even fewer changes. Last year I discovered Capture 1 Pro 8 after a demo of Phase One backs. It is a RAW converter with limited tools for editing so does not entirely replace Photoshop. BUT, and it is a big ‘BUT’, the RAW conversions are far better; images are sharper with better colour separation. The other difference is the sharpening, it seems smoother and less obvious.

    I had one particularly difficult image in PS6 which was showing signs of chromatic aberration which was impossible to correct. In Cap 1 there was no such issue and the image was sharper. I printed both files at A0 for comparison, the difference is staggering. I now use Cap 1 for all RAW conversions and maybe do a little edit in PS6 if required.

    The usual caveat applies, no connection with any products other than as a paying user!

On Landscape is part of Landscape Media Limited , a company registered in England and Wales . Registered Number: 07120795. Registered Office: 1, Clarke Hall Farm, Aberford Road, WF1 4AL