Photo Note – Compressing for Emailing

The following text was kindly provided by Fred to assist members with the delicate task of emailing images correctly. Fred has put a lot of time and effort into this document and it would be nice to show appreciation next time you see him.

Terms used in the post are:
MB = Megabyte
KB = Kilobyte
JPEG = Joint Experts Photographic Group (.jpg extention on picture file names)

Preface for Waverley Camera Club I wrote these notes for the photographers in the bushwalking club, most of whom do not use software such as Photoshop. Unfortunately their emailed photos were often reduced to postcard size and quality, and occasionally were inconveniently large. Some were not attached to the email, but were embedded in it and were difficult to extract for use in a slideshow. Most contributors, even the experienced photographers, were unaware of the problems in their contributions.

I have revised the notes for placing on the WCC blog, because the EDI Steward is encountering similar problems in some of our contributions. If your projected images don’t look sharp or don’t fit the screen, please read on.

Fred Bullock, 23 June 09.

Email is a handy vehicle for sending photos. Problems are unlikely if you use a tool like Photoshop to resize your pictures for emailing and then use the email application’s own attachment tool to attach it.

Unfortunately, many photos are spoiled by the obscure settings of other photo and email tools, usually by excessive resizing down to postcard or thumbnail size, which destroys detail, sharpness and quality. Also some settings embed the photos into the email’s body making them difficult to extract and save in a slideshow etc.

These problems are not apparent to the sender, only the recipient is aware unless the sender is aware of them. To check this, note the file size of the photo’s .jpg icon which is actually in the email’s attachments header, and double-click on it to inspect the picture (ignore any picture showing in the body of your email). If the photo’s icon is not in the attachments header, or if the file size is too large, or if it opens as a small or blurry or blotchy picture, please read on.
Sometimes re-compression is not done until the email is saved or sent (eg compressing within MS Outlook), so also check the email when it is in the Draft folder, Outbox or Sent Items folder. (If you open an email which is in Outlook’s outbox, you may have to click ‘Send’ again, otherwise it will not be sent even when you click Send All).

Please continue to use the highest quality settings on your cameras so you can tweak your photos and still get high quality large prints occasionally. The photos are usually lightly compressed by the camera, to about 5 MB depending on the camera. However it’s easier to email photos if they are re-compressed so that sufficient quality is retained. They transmit faster and there is reduced congestion in the recipients’ mailboxes.

The settings for the email tools are usually adjustable, but often hidden. The settings described in this note yield photos fit for projection, yet they have about 200 to 400 kByte file size and are fairly easily emailed.

General guidelines and guidelines for some Windows email tools and popular photo software are shown below. Moderate PC skills are assumed. The descriptions are cryptic, so it is best to follow those for your chosen compression tool while you operate it. The exact procedures may differ because of software upgrades or individual PC configuration.

General guidelines A typical 10 Megapixel camera takes and stores images about 3900 x 2600 pixels in size, compressed with the JPEG algorithm from 30 MB to about 5 MB. JPEG is the Joint Photographic Experts Group of the International Standards Organization, and computers use the .jpg suffix for the files.

Most resizing tools provide a combination of resampling and JPEG re-compression. The JPEG re-compression control is often just labelled “quality”. JPEG needs more processing power than resizing, but usually yields superior quality for the same file size.

The data projector resolution (what it shows on the screen) is width 1024 pixels x height 768 pixels. So, first set the resize control to fit a 1024 x 768 window.

Then set the JPEG compression quality to produce a compressed file size of about 200 to 400 KB. Unlike resizing, JPEG compression does not reduce the image size (pixels) and largely retains the sharpness remaining after the resizing step. (If used excessively it causes randomly blotchy tones, or ripples at hard edges, and in extreme cases its 8×8 blocks of pixels become visible).

Unfortunately different tools have different descriptions of each level of JPEG compression (quality). Some tools show an estimated file size before doing the processing, but this can be very inaccurate. So a little trial and error may be needed – start again with your originals, not with the incorrectly compressed photos.

The email commands in some photo programs may not work with some email applications, sometimes merely because the default email setting of the computer and the application are inconsistent. Otherwise there is usually an edit or export command that can be used instead.
With all exporting or editing tools, take care not to overwrite your original photos.
Some Useful Photo Tools

Windows XP, Send To > Mail Recipient command
This is a simple and widespread tool, best used as follows. Right-click on the selected photo file icon(s) and select Send To > and ‘Mail Recipient’ in the cascaded menus that appear. Then in the dialog box that appears, click Show more options… and click the ‘Make all my pictures smaller and the ‘Large’ (fits in a 1024 by 768 window) buttons. The JPEG compression quality is not adjustable. Click OK to create the email.

Windows Vista, Send To > Mail Recipient command
Right-click on the selected photo file icon(s) and select Send To > and Mail Recipient in the cascaded menus that appear. Then in the dialog box that appears, select Picture size: Medium: 1024 x 768. The JPEG compression quality is not adjustable. Click Attach to create the email. Beware that the Vista version of this application generates noticable fringing of some fine patterns, eg in photographs of feathers, but it is OK for general photography.

Picasa (a freeware photo manager, owned by Google)
Picasa fits horizontally oriented photos correctly to XGA resolution (WxH 1024×768) but incorrectly fits vertically oriented photos to WxH 768×1024, which is larger than required and these will be resampled by the club’s PC.Picasa’s Email button must be set up before use. The email settings are stored in its Tools menu, Options dialog box, Email tab. Choose which email client is to be used. Set the resize slider full right (1024 pixels) and click the 1024 pixels button just below it. The JPEG compression quality is not adjustable. Make sure the Send as HTML storybook button is not ticked because it embeds the photos. Click OK to store the settings.

Then select some photos and click the Email button to create an email. Use the Export button if the email button doesn’t work with your email application or if you want more options. Select some photos and click Export. In the dialog, browse to a temporary export location, click Resize to and set to 1024 pixels, set Image Quality to Normal or to Minimum. Click OK to export the compressed photos. Attach the exported photos in your email application.

Microsoft Outlook (comes with MS Office Professional)
(This paragraph was contributed by an Outlook user.) Create a new message and attach your photos with Insert, File command or the paperclip button (do not use Insert, Picture because that command embeds the photo in the mail message). Then click on the Attachment Options button next to the attachment line and select under Picture Options the picture size Large (1024 x 768 px) from the drop-down menu.

The JPEG compression quality is not adjustable. The file size of the attached photos does not change at this stage, the smaller file size will be apparent only after saving to the Drafts folder or having pressed the Send button (look in your Sent Items folder or in the Outbox if the actual transmission is still pending). If the Attachment Options button does not show, use the Options command to get it.

Microsoft Outlook Express
The Insert, File function is not available in Outlook Express, the lightweight version of Microsoft Outlook. Re-compress using a photo editing application and then attach the saved re-compressed photos with Outlook’s Insert, File Attachment command or the Attach (paperclip) button. Or use the Windows Send To > Mail Recipient command (see above), or the email command of a photo application.

Photoshop Elements
Open the picture and do the required cropping and editing (levels adjustments etc) before downsampling it.

Crop without resampling by selecting the crop tool and clicking the Clear button in its options bar, then do the cropping. To constrain the crop shape (eg to the projector shape) set suitably proportioned and easily remembered dimensions like 1024 cm x 768 cm and clear the Resolution box. The units of size (cm, inches etc) do not matter for projection, but do not set dimensions in pixels (eg 1024 px x 768 px), because that will invoke downsampling before you have done the editing.

To resample an image (after editing it), in the Image menu choose Resize > Image Size. In the dialog box, select Resample Image and choose Bicubic interpolation (and the options of superior interpolating filters or some sharpening may be available in later versions of PSE). Select Constrain Proportions . In Pixel Dimensions, enter values for width or height, choose pixels as the unit of measurement. Depending on the shape of your picture, set W = 1024 and check that H is 768 or less, or set H = 768 and check that W is 1024 or less. Click OK. The image will be shown as a smaller size on screen. Zoom in to check the quality. Some sharpening may improve the quality.

Save As a new file using the competition format for the filename. Select the JPEG format and tick ICC Profile. Click Save and in the next window select Medium or High quality and Baseline (Standard) format. Tick Preview to see an estimate of the file size, adjust the quality to change the size if required. Click OK.

Attach the picture(s) from within your email application. Or use Photoshop’s File menu, attach to E-mail command which creates an email and attaches the current picture.

This is freeware, quite handy for slideshows and image file manipulations.

Open the picture and in the Image menu select Resize/Resample… , and in the dialog box select or tick Set new size, pixels, Preserve aspect ratio, and Resample, and in the Resample filter box select the Lanczoss filter. Depending on the shape of your picture, set Width = 1024 and check Height is 768 or less, or set Height = 768 and check Width is 1024 or less). Selecting Apply sharpen after Resample may give a better looking result. Click OK. Then Save as a new file using the competition format for the filename. In the Save Picture As … dialog box, tick the Show options dialog button to get more control, importantly it is possible to set the JPEG quality, eg to 90%. Check the file size and image quality after saving.

Other photo software
Please discuss it with us.

Software to avoid
Microsoft Office Picture Manager (comes with MS Office) Be very wary with this application. When its edit tool is used for compression, it easily overwrites your originals even after you have saved the edited images under a new filename – always copy your originals before using this application and work only with the copies. Also, the edit tool or Picture button produce noticable fringing of fine detail (eg coarse ripples in photos of feathers) There is little reason to use this application unless you want to edit your pictures – and there are alternatives for that.

However MS Vista users who have problems with fringing of fine patterns when using the Send To > Mail Recipient command may find this application solves the problem, but Picasa is much easier and safer to use for equivalent results.

Microsoft Picture It! (a lightweight photo editor that came with MS Works) Avoid this tool entirely because it produces coarse and ugly fringing and blotchiness of fine detail (eg very coarse ripples in photos of feathers).

Fred Bullock