Was miniDV impossible to use for digital photography?

Archived from groups: rec.photo.digital (More info?)

On 4 Jun 2005 10:50:34 -0700, "Mike Henley" <casioculture@gmail.com>
wrote:

>Well, not only that, but this is despite the fact that the S1 stores a
>far more compressed video than the miniDV's, but anyhow, Since miniDV
>was a digital medium, why wasn't it ever used for photography, since it
>seems capable of storing far more data than much of solid state cards?

Tape is linear access, while the Flash RAM used in cameras is random
access.
Flash RAM is solid state; tape requires a mechanical transport
mechanism (think batteries!).

--
Big Bill
Replace "g" with "a"

Archived from groups: rec.photo.digital (More info?)

Dave Martindale wrote:
> Guy Jordan <gjordan@mn.rr.com> writes:
>
>
>>>This is exactly what my Canon Ultura MiniDV camcorder does in "photo"
>>>mode. It records a still frame for several seconds. Due to the low
>>>pixel count, and hassle getting the images (you need video caputure
>>>and editing software to get your individual frames), it isn't very
>>>usefull.
>
>
>>This is no different than recording computer date on tape; it was done
>>for years and worked well. It certainly fell out of favor lately but is
>>still used for network/server back-up and could be used for off-loading
>>data from solid state memory... but don't hold your breath for it. It
>>flies in the face of "established truth" to store image data on anything
>>but flash memory and a computer.
>
>
>>Marketing success does not equal product superiority, just a sheep
>>mentality in the audience.
>
>
> No, there are large technical differences. Rather than learn anything
> about them, you seem to see a conspiracy instead.
>
> Computer tape drives that can write single data blocks starting from a
> standstill without backing up the tape do exist, but they are large and
> expensive due to the accelerations needed to start and stop the tape
> without wasting most of the recording area. And recording density is
> not high compared to helical-scan recording.
>
> You can build streaming tape drives cheaper, but streamers require a
> continuing flow of data to keep the tape running at speed. If you don't
> keep the data flowing fast enough, the tape has to stop, back up a ways,
> then start up again, drastically reducing throughput. Thus, these
> drives aren't very suitable for still photography. The quarter-inch
> cartridge tapes and some half-inch reel tape drives worked this way.
>
> High-density backup drives mostly use helical scanning, just like MiniDV
> camcorder drives do. These can't write a single track with the tape
> stopped, even if the head drum is spinning - the tape has to be moving.
> So they also require a continuous flow of data to keep writing to tape.
> In addition, unlike the QIC drives, you can't leave the drive in "ready
> to write" mode with the drum spinning and the tape under tension for
> very long without wearing a hole in the tape oxide, so the drives need
> another standby mode that takes even longer to get ready to write.
>
> Finally, helical scan tape drives take a fair amount of space for the
> head drum and mechanical tape transport, and they eventually wear out.
>
> So tape works well for video, where the few seconds of intial startup
> delay don't matter, the data flow is continuous and steady, and the
> total amount of data is large. Helical tape formats work well for
> computer backup for the same reason.
>
> But in a still camera, flash RAM or a small hard disk (microdrive) is
> smaller, is ready instantly (flash) or in a fraction of a second
> (microdrive), and takes much less space and power than a tape drive
> capable of the same data rate. It just doesn't make sense.
>
> Dave

Dave-

What I know about tape drives was and is sufficient for this mental
exercise which had nothing to do with conspiracies and everything to do
with market pressures.

The mechanical natures of tape drives and data packing would still allow
a large memory buffer in a camera to transfer to a tape in batches. One
or two gig batch transfers may not be AS efficient as a a continuous
data stream able to fill a tape, but could still be functional. I don't
think your points invalidate my position.

On the face of it, your reaction lends creedence to the heretical nature
of my comments... and I will stand by my closing statement.

-Guy

Archived from groups: rec.photo.digital (More info?)

fotocord@yahoo.com writes:

>Might be a good idea for an "image bank" device to download cards to? DV
>tapes are avalible everywhere and it seem like it would be simple enough to
>devise a way to use them for this? Since most DV devices upload via
>firewire, the upload speeds should be pretty fast as well.

DV drives operate at 25 Mbits/sec, or about 6 Mbytes/sec. This is a
respectable speed, but many flash card devices beat it.

Basically, the advantage of tape is cheap storage per byte, at the cost
of an expensive and fragile tape handling mechanism, size, and power
consumption. This *does* make some sense in an "image bank" device when
you're shooting lots of images. It makes much less sense to include
this as part of the camera.

Dave

Archived from groups: rec.photo.digital (More info?)

Dave Martindale wrote:

> fotocord@yahoo.com writes:
>
>>Might be a good idea for an "image bank" device to download cards to? DV
>>tapes are avalible everywhere and it seem like it would be simple enough
>>to devise a way to use them for this? Since most DV devices upload via
>>firewire, the upload speeds should be pretty fast as well.
>
> DV drives operate at 25 Mbits/sec, or about 6 Mbytes/sec. This is a
> respectable speed, but many flash card devices beat it.
>
> Basically, the advantage of tape is cheap storage per byte, at the cost
> of an expensive and fragile tape handling mechanism, size, and power
> consumption. This *does* make some sense in an "image bank" device when
> you're shooting lots of images. It makes much less sense to include
> this as part of the camera.
>


That was my though. Using it on the camera doesn't make sense but something
like a battery powered DV tape device to dump CF cards into in the field
does.
--

Stacey