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Sony MVC-CD250 Sony adds features, and brings the price down on a 2 megapixel CD Mavica! Select a topic Reference: Datasheet MVC-CD250 Photo Gallery! MVC-CD250 Sample Images --------------------------------- 1. Intro and Highlights 2. Executive Overview 3. Design 4. Viewfinder 5. Optics 6. Exposure & Flash 7. Shutter Lag & Cycle Time Tests 8. Operation & User Interface 9. Camera Modes & Menus 10. Image Storage & Interface 11. Video, Power, Software 12. Test Results & Conclusion --------------------------------- Print-Friendly Review Version Additional Resources and Other Links Reader Comments on MVC-CD250 Review --------------------------------- Digital Camera Comparometer (TM) --------------------------------- <-- Digital Cameras (Home) <-- Digital Camera Reviews Index <<Camera Modes & Menus :(Previous) | (Next): Video, Power, Software>> Page 10:Image Storage & Interface Review First Posted: 02/20/2002

Image Storage and Interface
A small CD icon on the camera's LCD display lets you know how much of the disc is full and how many images are available, depending on the current resolution and quality settings. An "R" or "RW" below the icon lets you know what sort of disc is currently loaded in the camera. In Movie mode, the LCD reports the available recording time at the current movie quality setting. The CD400 allows you to protect individual images on the disc from accidental erasure or alteration through the Playback menu. The freedom of a CD-R drive has many advantages over saving images to floppies (as on some Mavica models), the main one being an increased amount of storage space -- 156MB.

It's important to note that there's a key limitation in Sony's CD-RW implementation, in that it's a sequential rewritable device, not a random access one. The reason for this is that the head movement and data clock synchronization requirements, which are dictated by true random access operation, would result in performance (write-time) tradeoffs that are unacceptable for digital camera applications. Thus, the "RW" aspect of the CD400's discs has some constraints on it. Foremost is the sequential operation, which means that you can only delete the last image recorded. That is, you can't open up more space on a disc by going back and deleting images shot earlier in the session. You can delete multiple images, but only one at a time, starting with the most recent and working backward. The huge benefit of CD-RW though, is that you can "unfinalize" and "format" discs, which (respectively) helps you save disk space when moving back and forth between camera and computer, and lets you reuse discs by wiping out all the previously captured images.

A brief note here, in response to some questions I've received about the earlier CD Mavicas: This issue of what constitutes "erasing" of an image and what images you can actually erase seems to be the cause of a lot of confusion. Several people have pointed out that the camera lets them "erase" images other than the last one shot, and in fact that they can do this on CD-R discs as well as CD-RW ones. You can always "erase" any image on either a CD-R or CD-RW disc, but you won't see a corresponding increase in storage capacity reflective of the space that the deleted image occupied. This is because "erasing" any image other than the last one shot (or any image on a CD-R disc) doesn't actually delete the image, but rather merely alters the disc's directory structure so that the "deleted" image no longer appears. You can only truly erase the last image on the disc, and then only on CD-RW media.

There's another generic limitation of CD-RW technology that prospective users need to be aware of, which is that the signal level delivered to the CD-ROM drive by CD-RW discs is quite a bit lower than that from normal CD-ROMs or CD-R write-once discs. Thus, some older CD-ROM drives may have trouble reading the CD-RW discs. As far as I know, any CD-ROM drive manufactured in the last three or four years should be able to read a CD-RW disc with no problem, but if you encounter difficulties, try a different CD-ROM drive before assuming it's a problem with the CD-RW disc or the CD-300 itself.

Using the CD-Rs in the camera is relatively simple. Whenever a new disc is inserted, the camera will tell you that it needs to be initialized. Not being a CD maven, I suspect (but am not sure) that this involves writing the "lead in" area for the next session, a roughly 9MB area reserved for the table of contents information for the upcoming session. Initializing the disc appears to be a more critical operation than normal CD-R recording, as the camera asks you to place it on a level surface and avoid vibration during the process. Once a disc has been initialized, operation of the CD400 is the same as for any other Sony camera, regardless of media.

When you're done with a set of shots and want to set up the CD-R to be read in a conventional CD-ROM drive, you must "Finalize" the session. The camera leads you through this process using menu screens similar to those used for the initialization process. Finalizing also appears to be a more critical procedure than normal image writing, since the camera again asks you to rest it on a flat surface. My guess is that this process writes the lead out for that session, and goes back to fill-in the session's Table of Contents in the lead-in area. The first lead-out on a disc occupies about 13MB of space, subsequent ones require about 4MB. The space taken by finalizing and reinitializing a disc leads to one of the major benefits of CD-RW technology over CD-R. With CD-R, every time you finalize and reinitialize a disc, you lose about 13MB of storage space. With CD-RW discs, you can "unfinalize" a disc, recover that space, and allow the camera to write new images to it. Additionally, unfinalizing a CD-RW doesn't erase any files. To completely erase all images on a CD-RW, the CD400 offers a Format option through the Setup menu, which also requires the camera to rest on a level surface with no vibrations. The Format function takes several minutes to complete. It's my guess that the camera is actually rewriting the entire disc, restoring it to a completely blank, initialized state. NOTE that unfinalizing and formatting are only possible with CD-RW discs, not ordinary CD-Rs.

In addition to finalizing a disc, the Playback settings menu allows you to write-protect, delete (sequentially), resize, or rotate individual images. When an image is resized, the original version is left where it is on the CD, and a new copy is appended to the end of the list of images, resized to the dimensions you selected. Rotation is much more confusing. The original image actually remains in place (even on a CD-RW disc), and a new, rotated version is recorded. The camera edits the directory structure of the disc though, so the new rotated version appears in the same place as the original, in the list of images as you step through them sequentially, or view them as thumbnails. Although the original image is still physically recorded on the disc, it is no longer accessible to either the camera or a computer. (I'm not sure, but some data-recovery programs may be able to retrieve "overwritten" or "deleted" files like this from the CD-R discs.)

You can also designate whether the camera numbers each image sequentially (from one CD to the next), or restarts file numbering with each new CD, by making a change in the Setup menu. The camera's Digital Print Option Format (DPOF) compatibility allows you to mark specific images for printing. Through the Setup menu you can decide whether or not to print the date and/or time on the image as well.

Image Size options include 1,600 x 1,200, 1,600 (3:2 ratio), 1,280 x 960, 640 x 480, and 320 x 240 pixels (E-Mail recording option). Movie file sizes are 320 (HQ), 320 x 240, and 160 x 112 pixels for MPEG Movies, or 160 x 120 and 80 x 72 pixels for Clip Motion files. In addition to the uncompressed TIFF file format, the CD250 offers both Fine and Standard JPEG compression levels, and a GIF option for the Clip Motion recording mode.

The table below shows the approximate still image capacities and compression ratios for the CD-R disc (main resolution sizes):

 

Image Capacity vs Resolution/Quality 156 MB CD-R disc		TIFF	Fine	Normal
High Resolution 1,600x1,200	Images (Avg size)	19 5.76MB	131 1.2MB	235 664KB
	Approx. Compression	1:1	5:1	9:1
Standard Resolution 1,280x960	Images (Avg size)	N/A	195 800KB	346 451KB
	Approx. Compression	N/A	5:1	8:1
Lowest Resolution 640x480	Images (Avg size)	N/A	657 237KB	1288 121KB
	Approx. Compression	N/A	4:1	8:1

 

Notes for Mac owners: In order to avoid a 1MB limit on writeable file size, Sony had to go with the Level 3 ISO CD standard, which supports larger data sizes in packet-writing mode. This means that Macs need a UDF format extension to be able to read the resulting discs. NOTE that the "UDF Volume Access" extension that ships with OS9 is apparently not adequate to the task. Although Apple's UDF Volume Access claims support for Version 1.5 of the UDF ("Universal Disk Format (tm)") specification, the Adaptec UDF Volume Access Version 1.04 extension is apparently required to read the version of the UDF format used by the Mavica MVC-CD400. I can, however attest to the fact that the iMac supports both the 80mm disc size, as well as the Adaptec Volume Access extension, as I was able to successfully read "finalized" CDs from the MVC-CD400 on our slot-loading iMac. (A 400MHz DV model, running Mac OS 9.0.4.)