Picture Transfer Protocol

Picture Transfer Protocol (PTP) is a widely supported protocol developed by the International Imaging Industry Association to allow the transfer of images from digital cameras to computers and other peripheral devices without the need of additional device drivers. The protocol has been standardised as ISO 15740.

It is further standardized for USB by the USB Implementers Forum as the "still image capture device class". USB is the default network transport media for PTP devices. USB PTP is a common alternative to USB MSC, as a digital camera connection protocol. Some cameras support both modes.

PTP specifies a way of creating, transferring and manipulating "objects" which are typically photographic images such as a JPEG file. While it is common to think of the objects that PTP handle as files, they are abstract entities identified solely by a 32-bit object ID. These objects can however have "parents" and "siblings" so that a file-system–like view of device contents can be created.

A number of protocols have been developed that extend PTP. PTP/IP, developed by FotoNation and first implemented in a round of WiFi digital cameras by Nikon, Canon, and Eastman Kodak, allows data transfer over any IP-based network.

Nikon also recently launched an adapter WT-4 that runs on the PTP/IP protocol [The WT-4] . While it employs a cable (USB) connection, this device is also a very high-performance wireless transmitter, offering diversified image transfer capabilities when connected with the Nikon D3 or the Nikon D300. It works in conjunction with the ‘Camera Control Pro 2’

When running on wireless LAN, the device supports IEEE 802.11b/g (180m approximate transmission range) and IEEE 802.11a (260m approximate transmission range). Of course, this range varies with obstacles and radio wave conditions.

Apart from PTP-IP, this device also employs the FTP communications protocol. The security access method employed is the infrastructure mode/Ad-hoc mode.

Media Transfer Protocol, developed by Microsoft, allows for transfer over wireless or wired networks based in part on FotoNation's PTP/IP, but also allows users to transfer other media aside from pictures, as well as for tagging objects with extended metadata (such as title, artist and similar).

Both Microsoft and Apple include PTP support in their operating systems, from Windows Me onwards (excluding Windows CE), and Mac OS X v10.1 onwards, respectively. Microsoft implements PTP on Windows through Windows Image Acquisition. [ [http://msdn2.microsoft.com/en-us/library/ms630343.aspx Windows Image Acquisition on MSDN] ] [ [http://www.microsoft.com/whdc/device/stillimage/stillimg-connect.mspx#EXC Still image connectivity for Windows] ] PTP on Linux and other free software/open source operating systems is supported by a number of libraries, such as libgphoto and [http://libptp.sf.net/ libptp] , libraries used by applications such as digikam and f-spot.

PTP v1.1 (ISO15740:2008) is an update to PTP that has recently been published by ISO. A copy of the specification can be purchased here: [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=45344] As of the middle of 2008, most devices and Operating Systems do not yet support PTP v1.1. This updated version of PTP is fully backward-compatible with PTP v1.0, and offers optional performance, compatibility, and feature enhancements including:
* A mechanism for handling streaming content
* A mechanism to support multiple vendor extension sets
* Support for objects larger than the 4GB size limit set by PTP v1.0. By requiring 8-bytes for object size (UINT64)
* Support for retrieval of ObjectHandles in enumerated chunks. This may reduce long response times for some devices that possess large numbers of objects
* Support for arbitrary resizing prior to image transmission (Responder scaling). In PTP v1.0, image sizes might be requested in full-resolution or thumbnail size only
* Support for arrays of datasets. This can be used to reduce the number of required transactions necessary for device characterization from being a function of the number of objects on the device down to one
* A fast file characterization operation that exploits dataset arrays to request, in a single transaction, only the minimum data required to characterize a typical filesystem
* A new standard ObjectFormatCode to support the Digital Negative file format (DNG)

Drawbacks

* Renaming file objects directly is not possible without copying the file or rewriting it.
* Modification of file contents is not supported (the file needs to be re-transferred completely).

ee also

* PictBridge
* Digital camera
* Universal Serial Bus
* USB mass storage device class USB MSC — alternative protocol for digital cameras

References

External links

* [http://www.iso.org/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=37445&COMMID=&scopelist=PROGRAMME ISO 15740] , ISO.
* [http://www.i3a.org/pr_09_26_05.html Picture Transfer Protocol — PTP — Now an International Standard] , I3A.
* [http://www.microsoft.com/presspass/press/2004/sep04/09-29FotoNationMTPPR.asp Microsoft and FotoNation Team to Support the Media Transfer Protocol For Wireless Digital Still Cameras] , Microsoft PressPass.
* [http://ptp.sourceforge.net/ Free software with PTP support]
* [http://www.nikon.com/about/news/2007/0823_09.htm]