ASK RICK NOVEMBER
Next August sees the first total solar
eclipse visible in England for 72 years and many people are already planning
their trips to Cornwall to witness this spectacular event, and record it with
their camcorders, myself included.
I own a Sony TRV 95 and was a little
concerned at pointing it directly at the sun in case any damage was caused to
the CCD unit. Various dealers didn't seem to have much idea, but most agreed it
wasn't a good idea to aim the camera at such a bright source of light, although
they were not sure what the outcome would be.
Sony themselves were most emphatic that the camera should not be pointed
at the sun, but cold offer no advice on filters etc. However, people do
successfully video eclipses where they have occurred in other parts of the
world and I'm sure they don't all bur their cameras out in the process. Can you
offer any suggestions?
Pointing a camcorder lens at the sun will damage
the CCD image sensor, as surely as you would damage your own eyes by looking
directly at it. If you've ever used a magnifying glass on a sunny day to burn
things, you will know how powerful sunlight can be. It is possible to safely
record a solar eclipse, without the use of filters, and that's to shoot an
image of the sun. You could try experimenting with a telescope or a pair of
binoculars. The idea is to aim the telescope or bins at the sun, and project an
image from the eyepiece onto a screen immediately behind the eyepiece lenses,
and this is what you record. You could use filters but I wouldn't recommend it
as there's plenty of opportunity for something going wrong and CCDs are very
expensive to replace! However, for the record one of the most effective filters
for this kind of application is an exposed section of photographic
I was most interested in your reply to David
Clough (Video Camera August), regarding the capabilities of the Super VHS
format. I have always assumed that the inclusion of 'more than 400-lines' in
the specification of certain camcorders was a statement of fact and not faint
However, what interests me in the new DV era
is that the results of tests on DV camcorders seen to suggest that they do not
all achieve 400-lines. In these cases what is the advantage, apart from
faultless copies to infinity?
One other question if I may. Can one expect
that by connecting S-VHS apparatus to each other or to a TV with an S-Video
input, using standard SCART cable, S-VHS quality will be transmitted? In my Panasonic
NV-HS1000 instruction manual they seem to indicate a different configuration
for S-Video, but I have not been able to get a satisfactory answers from local
retailers on this issue.
Dr D. H. D. Burbridge
You will also read on the specification pages
of instruction books -- usually in fairly small print, notices that say
something like: 'we reserve the right to change the specifications without notice'.
That basically means the actual performance of the product need bear no
relationship what is printed in the manual. We tend to treat manufacturer's
specs as a useful guide, but by no means gospel. It's also worth pointing out
that resolution in the real world is dependent on an number of other external factors,
including the type of tape used, the connecting cables, the equipment on which
the image is analysed, and not forgetting the actual test conditions. It might
also interest you to know that a good number of domestic televisions --
including models fitted with S-Video inputs -- are incapable of displaying the
fine detail contained in high-band video recordings, which makes the
performance of the camcorder largely academic. One last point and this has some
bearing on your comments about DV camcorders. Our eyes are far more sensitive to
picture noise, than resolution. We tend to notice the noise content in a video
image long before the amount of fine detail, and you can get the situation
where a noisy high definition image will actually look worse than clean recording
made on lower definition equipment. Digital recordings tend to have very low
levels of picture noise, and unlike analogue recordings, it doesn't increase
when recordings are copied, which is critically important when editing.
THANKS FOR THE MEMORY
I am aware of the fact that NiCad batteries
can suffer from memory effects and I am careful to discharge them before
recharging. What is the cause of these memory effect and could they occur if
the electricity supply is interrupted during recharging?
We used to get a lot of letters about
batteries. Improvements in camcorder power management systems and a new
generation of nickel metal hydride or Lithium ion packs have made a life a lot
easier for us all. Nevertheless there's still plenty of nicad powered machines out
there, so a quick recap wouldn't come amiss. The so-called 'nicad memory'
effect usually refers to the way a battery pack gradually looses its ability to
hold a full charge. In extreme cases it's possible for a battery pack to loose
up to 50% of its capacity in just a few months. Inside a nicad battery there's
a bank of individual cells, connected together in series, (and parallel in the
case of higher capacity packs), to produce the required voltage. No two cells
are exactly alike, and over time the state of charge of the cells in the pack
will vary. Fast battery chargers, of the type supplied with camcorders,
determine when the battery pack is fully charged by analysing the voltage of
the pack, when it senses a small change it decides the pack is charged and cuts
off, or reverts to trickle charge. This small change in voltage can occur when
just one or two of the cells inside reach full charge, leaving the others and
thus the pack as a whole only partially charged. Discharging the pack brings
all of the cells back into line once again. NiCad memory develops quickly when
packs are repeatedly subjected to shallow charge/discharge cycles or 'top-ups' -- i.e. the battery is charged before it has
been fully discharged. A power failure whilst charge won't damage the battery,
it will simply resume charging when the power is restored.
I desperately need help in locating a
stand-alone Genlock, which I realise is 'old technology'. I do no have a PC so
a frame grabber cannot be used. I simply want to superimpose titles over moving
video. I have tried many suppliers but to no avail so far. Hopefully you have
access to companies who may still have old stock?
Are you sure you mean a genlock? They are
normally used to mix graphics generated on PC (and other devices) with moving video.
A genlock usually requires one of the two
video sources to have an external synchronisation facility, enabling the two
signals to be combined. A frame grabber
works the other way around, capturing video information and converting it into
a PC image file. It sounds as though you want to create a title, shoot it with
a camera and combine it with moving video, in which case you need a digital video
mixer. In this case one video channel is converted into digital data and stored
temporarily in a memory, then read out so that it is in perfect synchronisation
with the second channel. That's quite a trick and it doesn't come cheap. Check
out the RoMaster DVR-300 and Camlink Vision 1000, both of which are selling in
the £400 to £450 price bracket. If you only want to create simple titles, then
there are several dedicated title generators on the market, with built-in genlocking
facilities. Prices start at around £120.
I wish to make a video copy, on VHS-C, of
some cine film that I shot in Canada several years ago. I would like to send a
direct camcorder copy to my relatives in Canada, but I am unsure if they would
be able to view the copy on their VCR. Could you tell me if it is feasible, even
if it is a case of 'vision-only' and no sound? I'd appreciate your comments.
Bad news I'm afraid. We in the UK use the PAL
625-line/50Hz colour TV system. Over in Canada they use the 525-line/60Hz NTSC
system. The two are incompatible and any recording you sent them, made on a PAL
camcorder, would be an unviewable mess. Ironically, you would be able to watch
recordings sent from Canada quite easily as many recent VCRs can replay NTSC
recordings on PAL TVs. Unfortunately this trick doesn't work the other way around.
The simplest solution is to have the movie film professional copied onto an
NTSC recording, you will find several companies advertising such a service in
our classified section. Other alternatives would be to use an NTSC camcorder
(maybe next time your relatives are over here, ask them if you can borrow
theirs), or you could use a multi-standard 'transcoding' VCR like the Samsung SV-4000W,
which can digitally convert video recordings from one standard to another. This
machine currently sells for just under £1000.
I am a complete novice where video cameras are
concerned and admit to being totally confused with regard to the wealth of
models and types on the market. If I detail my requirements perhaps you could
suggest some models which generally meet my criteria. Initially I would be
seeking a camera, which can be fitted with a prescription lens to the
viewfinder, and I would prefer a colour viewer. Then I would require a camera
lens equal to the performance of a quality 35mm still camera and a zoom facility,
capable of picking up low flying aircraft, without any visible 'judder' in the
picture. I would like a camera with extremely simple controls, such as
on/off/shoot, without having to fiddle with exposure etc. Then I would prefer
to be able to use off- the-shelf batteries. Actual running times should be in
the region of 2 hours, plus. I would like to use standard VHS cassettes, or the
type, which can be loaded into a conventional video player. Price is of no
object and I would prefer total reliability under all operating conditions.
Accessories should include a rain shroud.
Keith R. Bennett,
Taking those points one at a time, virtually all
camcorders have a 'dioptre' adjustment on the viewfinder eyepiece that can
accommodate all but the most extreme vision defects. The zoom lenses fitted to
most camcorders can cope easily with recording at air shows etc.; if by 'judder'
you mean erratic or jerky zoom action you have no need to worry, the motorised
zooms on all current machines are very smooth. All camcorders -- even the most
expensive semi-pro machines --have fully automatic focus and exposure systems, designed
for effortless point-and-shoot operation. Some camcorders have optional (or
supplied) dry battery packs but they are really for emergencies only, the
supplied battery packs can be re-charged, and higher capacity models are freely
available. You would be very lucky to find any machine that will run for up to
2 hours on a standard battery.
You express a preference for VHS-C, (I
hesitate to suggest any VHS/S-VHS machines as they fall down badly on the price/performance/portability equation) and a
colour viewfinder, which narrows the choice to the Panasonic NV-SX50 (£800), as
the only machine that comes anywhere close to meeting your key requirements.
However, I urge you to reconsider some of those criteria, especially concerning
the format. It's really not that important as you will almost certainly want to
edit or copy your recordings to VHS, in which case the camcorder tape format is
irrelevant. That will allow you to broaden your choice of machines to include
Hi8 and DVC models. Look through the Buyer's Guide in the back of the magazine,
and try out a few for size at your local video dealer.
ã R. Maybury 1998 2408