How to Accurately Crop Slide Images

Ever wonder how to accurately crop slide images? Digital images don’t need to be cropped to a standard size like printed photos do. Your computer will resize the digital images to fit your screen, no matter what size or resolution it is.

When we scan a slide, we cut the image just 30 thousands of an inch from the edge of the slide frame. When we scan a printed photo, we cut the image as close to the physical edge of the print as we can and still make a rectangle. Later, if you decide to have prints made from your digital images, you choose the print size, orientation and location using your computer.

So, if you have the slides and the printed photos, slides would probably be the best to send us. It is just easier to crop them.

Crop Slide Images With DpsDave Slide Scanning Services

There are important cropping considerations based on the slide size. For a 126 slide in 2” x 2” mount, the viewable area is usually 26.5mm x 26.5mm. The aperture of some scanners (36.8mm x 25.1mm) is limiting so that the scanner “doesn’t see” about 1.45mm from both the top and bottom. For a 127 “super slide” in a 2” x 2” mount, the viewable area is 40mm x 40mm. A significant portion cannot be scanned, again, due to the aperture of the scanner. Most slide mounts crop the image slightly less than 24 mm x 36 mm. A slight shift of film in a mount can further reduce the useable image area.

Cropping generally eliminates the white slide holder, changing it to black once it is scanned. If a slide has rounded corners, these can be purposely cropped out to give an image a cleaner look to its edges. If a certain portion should be cropped out, DpsDave can see in a scanned preview window beforehand to make sure that no details of the image that the customer wants in the photo are deleted.

Our scanners are pretty good at detecting the edges of the slides, but be aware that some scanners are automatically set up to crop 35mm slides—so if you have a different size, settings will need to be changed. Another important consideration is that the area selected in a crop is not only the area for the output file, but also a way to calculate color balance, histogram and other settings. The real image could be underexposed unless balance is set for each individual slide before it is scanned. If not cropped a certain way, the slide scan quality may be impacted and require much more post-scan editing. This is why DpsDave doesn’t recommend our potential customers try to scan slides themselves.

Additionally, some clients who put strips on the glass to scan, experience what is known as Newton rings. Newton rings may form due to interference created by a light reflection from a flat surface to a spherical surface. Droplets of moisture can cause a concentric ring pattern. One way to prevent this may be to cut a negative or slide and leave it under a flat item for a bit before scanning. Then, one can add back in a white border in Photoshop after the scan to fill in what was cut. Avoiding Newton rings can lead to a tedious process if you are new to the concept and process of avoiding them.

Our team is aware of Crop | Buffer % settings that can prevent inclusion of data outside the desired frame in color settings. Other crop scan settings to take into consideration include Manual Crop, Auto Crop and Maximum Crop.
There are also offset, spacing and padding settings to be considered. It isn’t always as easy as it looks to get the right settings!

Many flatbed scanners have transparency adapters that hold multiple negatives or slides, so there are Crop | Multi Crop settings for cropping batches of these. DpsDave has the equipment and scanners to handle large batches of cropping. In some cases, people run into issues where they still manually have to set individual slide cropping, because slides are slightly different from one another and can’t be cropped perfectly through batch slide cropping. Although batch processing is a time saver, we will not do it if we can’t make sure every slide comes out cropped to perfection!

Other than a preventive approach to cropping, sometimes cropping is done as a proactive approach to making the photo look better in the customer’s eyes. For instance, oftentimes a little cropping can improve composition of images, making the actual subject appear larger. You may have one slide image where the subject is close up and cropping further would not be the best idea, or you may have other slides that are zoomed out and you can hardly make out who the subject is. In the latter case, cropping may be a good idea to consider.

Crop Before or After Scanning

Some photographers buy cameras and lenses with the goal in mind of preventing having to do extensive cropping later. For crop-sensor Canon DSLR’s, Canon EF-S 60mm macro lens is very popular. If you have a “crop sensor” camera like DX or APC-C, the same 1:1 lens would give you an effective 1.5:1, therefore magnifying. Type of camera and distance from subject are all factors for photographers to take into consideration.

If we are being honest though, you probably were not the photographer of the slides you are sending to DpsDave, and you may not even be into photography period. Even if you were into photography, you might have used a digital camera and not be so worried about scanning of old slides. In this case, the problems may be unavoidable and cropping will be a consideration we look at before scanning your images. Let DpsDave take it from here!