Preview Sizes and Offline Editing in Capture One Pro 7

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Previews in Catalogs enable you to easy edit metadata, organize or make visual adjustments to your images, while on the go with no access to the actual raw file.

One of the great benefits of working with Catalogs in Capture One Pro 7 is the ability to work on your images – even when they are ‘offline’.

When you work with a Catalog in Capture One Pro 7, you can choose to store your original images inside the Catalog itself or you can store them at their existing location, for example on external hard drives.

The Catalog contains a preview image of every raw file in the Catalog, so even if you don’t have access to your storage media, you can still work with your image Catalog, edit metadata, organise it and even make visual adjustments.

Why do we use Previews in Capture One?

Every time an image is imported into a Catalog, Capture One Pro 7 creates an exact preview of the raw file and stores it within the Catalog.  Most operations in Capture One Pro 7 actually work with the preview, as it is much faster to use the smaller preview file than constantly having to read the much larger raw file.

Therefore, the images you see in the Browser and Viewer are the preview images. Capture One Pro 7 only needs to access the full raw file in order to show the image in the viewer if you need to view the image at 100% or if you work on a monitor with an extremely high resolution.  Capture One Pro 7 also does some smart caching, by reading images before and after the currently selected image thus making the shift to the next or previous image faster.

The preview will of course visually match the output image based on the adjustments made in Capture One Pro 7.

Preview Sizes in the Capture One Catalog

The size of the preview inside the Catalog file can be controlled by the Preferences Dialogue under the Image Tab.

prefs

By default, the preview size is set at 2560 pixels in Capture One Pro 7 while the preview size was only 1024 pixels in version 6. Because Capture One Pro 7 now uses a much smarter method for compressing the preview files, the new default preview at 2560 pixels takes up roughly the same space as the old preview at 1024 pixels in Capture One 6.

The new high resolution default preview in Capture One Pro 7 really gives you great benefits when you work with offline files. The 2560 pixels give such a high resolution that you may not notice that you are working with offline images. Typically, you can even zoom into the images to about 50% without missing details in the images.

If you are working a lot with your images offline, it makes sense to use a larger preview size. A large preview will increase loading times for previews in the application, but on more powerful computers this will be less noticeable. Larger preview image sizes will also increase the general size of the Catalog.

Catalog Size Comparison

The following table shows the Catalog size for different number of images and preview sizes for Canon 5D Mark III raw files placed outside the Catalog.

Nr. of images

1000

5000

10000

25000

%

RAW size( Gbyte)

28

140

280

700

100%

preview size = 2560 (default)

1.62

8.12

16.24

40.6

5.8%

preview size = 1440

0.53

2.63

5.26

13.15

1.9%

preview size = 1024

0.28

1.41

2.82

7.05

1.0%

preview size = 640

0.15

0.76

1.52

3.8

0.5%

From the table, you can see that using the default preview size at 2560 pixels only takes up 5.8% more space than the original raw files but you get such a nice and large preview file for working with offline files.  On the other hand, the Catalog will take up 40.6 Gbyte if you have added 25000 images.  So, if you find that the “offline” preview quality is good enough with 1440 or 1024 pixels, then your catalog can actually be considerably smaller.

Changing Preview Sizes

To change the preview size, simply select a new value in the pull down menu.

Any changes made here will only affect images imported after the change has been made.  The previews of existing images will have the size set in the preferences at the time of import.

If necessary, you can update existing images with a smaller or larger size preview by :

1. Choose the new preview size

  1. Select the images in the Catalog to be updated
  2. Go to File>Regenerate Previews.  The Activity Monitor will show the progress of the preview generation.

Existing previews will be replaced with the new preview size.  Subsequent imports will also be made with the new size.

This may be useful to do if you have in the past chosen a smaller preview size and would like the benefit of a larger preview size.

All the best,

Niels

The Image Quality Professor

Niels V. Knudsen

Niels V. Knudsen is Phase One’s Image Quality Professor. He is responsible for breakthrough advancements in image quality both in Phase One’s medium format camera systems and in its digital imaging software.

3 thoughts on “Preview Sizes and Offline Editing in Capture One Pro 7

  1. Per Ulrik

    Interesting information. A few days ago I set the value for the size of my screen, but did not realize where it had an impact.
    Thank you!

    Reply
  2. Edward (@edwardshred)

    Great information. I was also lucky to catch up with you recently Niels when you talked about this in London.

    A quick question if I may? Given that many users will wish to view at 100% (for close work), what is the fastest way of calculating the relevant preview image size for a given RAW (in my case D700 NEF) dimension?

    thx
    Edward

    Reply

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