Sensor

• 12 megapixel (MP) or greater.

Smartphone manufacturers inflate their megapixel ratings. When in doubt, find the resolution of a sample output image.

Multiply the width and length of the image (in pixels), then divide by a million (1,000,000).

For instance, a smartphone with multiple lenses marketed as having a “giant 108 MP sensor” output a sample image in 3072 x 4096 pixels. When multiplied, this is 12,582,912 pixels, rounded to 12.6 megapixels.

Also note that different lenses on the same smartphone may shoot at slightly different resolutions. If you already own the smartphone in question, check the results of your camera in different modes before using it in a field shoot.

Best cameras: interchangeable lens cameras

Interchangeable lens cameras have physically larger sensors than fixed-lens cameras with the same megapixel rating. This results in clearer details and less noise in the final image.

HPO recommends either of the following types:

Digital single-lens reflex (DSLR)

Images travel through the lens, then reflected into an optical viewfinder by a mirror and prism. You see the same image that the digital sensor will see. The mirror covers the sensor while you are using the viewfinder, then snaps up (blocking the viewfinder) during the exposure.

Mirrorless interchangeable lens camera (MILC)

Images travel directly to the sensor, which is constantly exposed. Viewing is through a digital viewfinder or display back only.

Acceptable cameras

The following cameras still produce acceptable results:

• Point-and-shoot/fixed-lens.
• Smartphone cameras, but do not use a digital zoom.

These cameras do not have removable lenses but most of the lens information on this page applies to these cameras as well.

Note that most of these have smaller sensors than full-frame (35mm film frame size) cameras, but some models have significantly smaller sensors than others.

Check the manufacturer’s specifications for more information about lens type(s) or sensor size.

Lenses

HPO recommends a lens or lenses capable of capturing:

• wide angle views of a resource or landscape
• normal perspectives of rooms and other areas with minimal distortion of straight lines
• close views of details

If possible, choose a “fast” lens that lets in more light for shooting indoors or under other low-light conditions. On most lenses, this rating starts with an “f/…”, with a lower number equaling a faster possible speed.

What lens size(s) should I buy?

The sensor size affects recommended lens sizes. Standard 35mm film cameras used the same frame size, but digital cameras have a wide range of sensor sizes. Your camera model’s documentation will state its crop factor, which can be used to translate 35mm/full-frame lens recommendations to your camera.

Start with a focal length for full-frame cameras, then divide by your camera’s crop factor.

For example, the most common focal length for a “normal” view, one that matches what you can see unassisted outside the viewfinder, is 50mm on a traditional 35mm film camera.

• If you have a full-frame digital camera, you do not need to calculate a new size.
• APS-C sensors have an average crop factor of 1.5x. So, you would need to divide the 50mm from above by that 1.5x crop factor to get 33-35mm for an equivalent focal length on an APS-C sensor.
• Micro Four-Thirds (MFT), used by many mirrorless cameras, is usually 2x. So, a “normal” MFT lens focal length would be 25mm.

Image quality

• RGB color.
• 6 MP (2000 x 3000 pixel) or greater image resolution.
• If zooming into details, use an optical zoom lens.

What is the best setting for my camera?

• If you can shoot in shoot in RAW (raw sensor dump) and have digital darkroom software, shoot in RAW and process directly into Tagged Image File format (TIFF) at your camera’s highest available resolution.
• If you have a camera capable of RAW but not digital darkroom software, a “RAW + JPEG” mode will provide both a JPEG that is immediately viewable and RAW files that can be processed into higher quality images for publications.
• Collect original RAW files as a supplemental file set for HPO’s image archive.
• If your camera has no RAW mode, use the highest quality JPEG setting and save copies of the unedited JPEGs directly from the camera.

Color mode

• Scan color film in RGB color.
• Scan black-and-white film and images in grayscale.

Image quality

• Scan directly to TIFF.
• Use a scanner capable of at least 1200 dpi.
• Use the highest optical resolution available for your scanner. This is the highest resolution your scanner can use without interpolation (approximating missing data). Your scanner’s manual will list recommended settings.
• If you cannot scan film yourself, order a disc or downloadable scans from your photo processor. Check your service’s scanning options before ordering. Large-format film will have more limited resolutions available than smaller formats.

Our office, and the agencies we work with, requires Tagged Image File Format (TIFF) for many image submissions regardless of the source. This is still the best format for long-term archival storage and is suitable for print use.

TIFFs saved specifically for archival purposes, such as National Register or mitigation documentation submissions, must be saved with options that make them readable on the widest variety of software and platforms. Use the following settings to avoid potential compatibility issues, especially for National Register nominations that will be later submitted to the National Park Service. Note, some of these TIFF settings are only applicable to Photoshop or other advanced image editors that prompt for them.

• Flatten all layers, including smart objects and dynamic layers. In Photoshop, if your image has “Layer [number]” as a single layer name instead of “Background” with a padlock, it is still a “layered” file and you still need to flatten your image.
• No compression in the final submission. If editing an earlier compressed TIFF on your computer, never use “JPEG” image compression.
• (Photoshop or similar) pixel order “Interleaved (RGBRGB).”
• (Photoshop or similar) byte order: “IBM PC.”

Color mode

• Scan strictly black-and-white content, like text pages, in bitonal black-and-white.
• Scan monochrome images with shading in grayscale.
• Scan color content in color.

Image quality and formats

• Use at least 300dpi for regular document pages. This is “press quality” resolution for printed content.
• Measured drawings and plans have fine linework and detail that cannot be captured in 300dpi bitonal black-and-white. Use 600dpi bitonal instead. If halftones or other details are too blurred or difficult to capture, use 300dpi grayscale.
• For sharing with others, convert your scans to Portable Document Format (PDF) at high quality settings. Follow one of the published PDF standards (“PDF [single-digit number]”) when saving your file. If unsure, use the archival PDF (PDF/A) option, which will not allow any nonstandard content. Adobe developed and shared the open standard, but not all Adobe Acrobat PDF features are open. Avoid using interactive content or other proprietary features, like PDF Portfolios, or the files may not work at all with other software.

In-house or commercial prints?

• If you print images yourself, use an inkjet printer and supplies specifically designed for photographic prints. Archival ratings are based upon specific ink and paper combinations, so use the combination(s) recommended by the printer manufacturer.
• Otherwise, professional services will provide higher-quality and more durable results.

Types of prints

• Images should be at least 300dpi (standard print resolution) at the physical size you wish to print.
• If using a professional service, use one with commercial photograph printers. Do not use a service that only has printers for office documents.
• Print color images in color unless otherwise instructed.
• Silver gelatin prints are more shelf stable than color prints of black-and-white photography. If you specifically wish to order silver gelatin prints, you will need to use a service that states they offer this type of print.