3200 K or 5600 K?
- Thread starter edwave
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Barry_Green
Moderator
Well, there's a lot to your question that would have to be answered. 5600k lights typically means HMI, and HMI lights are great for what they do, but they have their share of drawbacks too -- as in, they're EXPEN$IVE to buy new, and the more affordable used ones off ebay have magnetic ballasts, which hum, and which don't allow for hot restrike. So using HMI lights as your only light source is really inconvenient.
On the other hand, using tungsten lights outdoors with blue gel on 'em is practically useless in daylight. Blue gel cuts the light output to 1/4, so you'd need a really, really, really powerful light (2K and above) to be of really any use at all, and probably 5k or more to see much of any lighting effect on a sunny day.
So the only valid comparison would be in fluorescents. You can buy fluorescent tubes in 5600 and 3200, so you're using the same light fixture.
In that comparison, if you could *only* buy one color, definitely get the 5600's. If you can't have both kinds of tubes, the 5600 are the ones to get. Usually when you're shooting daylight-balanced, you need all the light you can get -- and 5600 tubes will not need any light-robbing color correction gels to output 5600k light. 3200k tubes would need CTB gel, and that would cut their light output to 1/4 -- exactly what you *cannot* have happen.
In indoors situations, you can put CTO gel on your 5600k fixture to convert it to 3200 degrees, suitable for indoor shooting. CTO gel only causes a light loss of 2/3 of one f-stop, vs. the 2 full f-stop loss for CTB gel. So in indoor situations you'd still be getting 2/3 of your total light output, and indoors you usually don't need that much output. And outdoors you'd be getting 100% light output, which is when you need it.
So if you're deciding between 3200k fluo's and 5600k fluo's, and you can't have both, then definitely get the 5600's and a sheet of CTO gel. That'll let you work in both environments, for the lowest overall cost.
On the other hand, using tungsten lights outdoors with blue gel on 'em is practically useless in daylight. Blue gel cuts the light output to 1/4, so you'd need a really, really, really powerful light (2K and above) to be of really any use at all, and probably 5k or more to see much of any lighting effect on a sunny day.
So the only valid comparison would be in fluorescents. You can buy fluorescent tubes in 5600 and 3200, so you're using the same light fixture.
In that comparison, if you could *only* buy one color, definitely get the 5600's. If you can't have both kinds of tubes, the 5600 are the ones to get. Usually when you're shooting daylight-balanced, you need all the light you can get -- and 5600 tubes will not need any light-robbing color correction gels to output 5600k light. 3200k tubes would need CTB gel, and that would cut their light output to 1/4 -- exactly what you *cannot* have happen.
In indoors situations, you can put CTO gel on your 5600k fixture to convert it to 3200 degrees, suitable for indoor shooting. CTO gel only causes a light loss of 2/3 of one f-stop, vs. the 2 full f-stop loss for CTB gel. So in indoor situations you'd still be getting 2/3 of your total light output, and indoors you usually don't need that much output. And outdoors you'd be getting 100% light output, which is when you need it.
So if you're deciding between 3200k fluo's and 5600k fluo's, and you can't have both, then definitely get the 5600's and a sheet of CTO gel. That'll let you work in both environments, for the lowest overall cost.
good..
good..
well barry, thanks for your complete answer first of all.
I have understood everything you say but you used some abbreviations that are surely different in my language.
for ex:
HMI stands for?
when you say: Blue gel cuts the light output to 1/4...i translate this as I lose 3/4 of my source light power right?
for CTO and CTB you mean just the orange and blue gels right?
so how much is about that fluos you talk about? can you tell me any store in USA which has cheaper prizes than here in Italy (not such an hard thing to find....!!)?
sorry for my poor "technic cinema terms" english!
ed
good..
well barry, thanks for your complete answer first of all.
I have understood everything you say but you used some abbreviations that are surely different in my language.
for ex:
HMI stands for?
when you say: Blue gel cuts the light output to 1/4...i translate this as I lose 3/4 of my source light power right?
for CTO and CTB you mean just the orange and blue gels right?
so how much is about that fluos you talk about? can you tell me any store in USA which has cheaper prizes than here in Italy (not such an hard thing to find....!!)?
sorry for my poor "technic cinema terms" english!
ed
khmuse
Tech Guru
HMIs (Hygerium Metallic Iodide) are an arc type of lamp that uses a mixture of gases to control the color temperature; they also require an upstream power supply or "ballast". The ballast can be either magnetic (passive) of electronic (active). These lamps and their power supplies are many time more expensive than other lamps but they can have very high optical output. Magnetic ballasts have the disadvantage of not being able to change their frequency so the mains frequency becomes the flicker rate of the lamp (like a florescent). Electronic HMI ballasts first convert the mains to DC then regenerate the HF output to the lamp head; which is usually frequency adjustable. With these types of ballasts you can then choose an output frequency which is non-coincident to the shutter speed that you are using.
CTO (available in a number of grades) is Color Temperature Orange
CTB (also available in a number of grades) is Color Temperature Blue
The advantage of HMIs or other 5600 degree light sources is that the blue gels have somewhat less light loss than the other way around. A definite advantage in terms of not throwing out a major percentage of your lights output just to change the color.
It is a great idea to have both CTO & CTB available (I keep several grades on hand) as it can be used for many situations.
CTO (available in a number of grades) is Color Temperature Orange
CTB (also available in a number of grades) is Color Temperature Blue
The advantage of HMIs or other 5600 degree light sources is that the blue gels have somewhat less light loss than the other way around. A definite advantage in terms of not throwing out a major percentage of your lights output just to change the color.
It is a great idea to have both CTO & CTB available (I keep several grades on hand) as it can be used for many situations.
For digital cameras, this makes absolutely no sense. Anyone recommending this doesn't understand the basic physics of light and how digital video cameras work. When you do a white balance, you're telling the camera that for a given set of voltages from the CCD's, you want the digital output of the R, G, and B signals to be equal. When R=G=B you have a neutral tone--anything from white to almost black.
Let's say you white balance under 3200K light or use the 3200K preset. The camera will be looking for a higher voltage off the R and G CCD's (R+G=yellow) in order to equalize the R, G, and B output. So far so good. Then you go outside and the camera is seeing lower R and G CCD voltages, so the output will look blue. So you slap on an 85b filter to compensate for the incorrect color balance. It may work,*but* you've added a yellow filter to your optical path. A yellow filter works by removing the blue wavelengths of light. So you've got less blue light hitting your CCD's. Not good. Why? Because CCD's are monochromatic sensors that are sensitive to a range of visible light, but are *less* sensitive to blue light. That's why the blue channel is always the noisiest. So you'd basically be adding extra noise to the system. Maybe not a lot because there a pretty high level of light outside, but it sure isn't going to help.
Let's say you white balance under 3200K light or use the 3200K preset. The camera will be looking for a higher voltage off the R and G CCD's (R+G=yellow) in order to equalize the R, G, and B output. So far so good. Then you go outside and the camera is seeing lower R and G CCD voltages, so the output will look blue. So you slap on an 85b filter to compensate for the incorrect color balance. It may work,*but* you've added a yellow filter to your optical path. A yellow filter works by removing the blue wavelengths of light. So you've got less blue light hitting your CCD's. Not good. Why? Because CCD's are monochromatic sensors that are sensitive to a range of visible light, but are *less* sensitive to blue light. That's why the blue channel is always the noisiest. So you'd basically be adding extra noise to the system. Maybe not a lot because there a pretty high level of light outside, but it sure isn't going to help.
GenJerDan said:
khmuse
Tech Guru
I basically agree with Barry's comment, but would add that any CCD has a somewhat non linear relationship between their output voltage and the spectral content of the sample. There is likely an optimum color temperature for any CCD design, one that maximizes the dynamic range and minimizes the noise characteristics. If known, then using filtration to achieve this "optimum" spectral balance could be beneficial.
It might be worth while to characterize the 100's CCDs to determine this optimum setting. Perhaps a simple test might be something like a looking at the linearity of each color channel over a large range of illumination levels to fully exercise the upper and lower limits of each sensor.
I don't know how much advantage that hitting the optimum point might provide, but given the limited dynamic range of SD video, it might give the last bit of achievable performance?
It might be worth while to characterize the 100's CCDs to determine this optimum setting. Perhaps a simple test might be something like a looking at the linearity of each color channel over a large range of illumination levels to fully exercise the upper and lower limits of each sensor.
I don't know how much advantage that hitting the optimum point might provide, but given the limited dynamic range of SD video, it might give the last bit of achievable performance?
GenJerDan
Veteran
You jogged a bit more of the memory with that 85B in there. That's just what they said to do...and I now recall that I read it *here*. And no one jumped in and said it was silly.
Of course, the search engine doesn't let you search for 85B, so I can't pull it up to double check the whys and wherefors.
It wasn't all that long ago, either.
Dan
Of course, the search engine doesn't let you search for 85B, so I can't pull it up to double check the whys and wherefors.
It wasn't all that long ago, either.
Dan
Yes, there's absolutely a peak spectral sensitivity for a CCD. You can see a typical CCD spectral sensitivity curve in the attached graph. Like most CCD's it has the highest sensitivity at longer wavelengths around green-yellow and is a bit hurting in the blue area of the spectrum. But, adding a filter can't increase the sensitivity in any part of the spectrum because filters only remove light. The CCDs are already receiving filtered light--R, G, or B. Either from a beam splitter or a filter over each CCD. That's how we get color from a monochromatic device like a CCD. The addititive color from Red + Blue + Green filtered CCDs=any possible color in the spectrum.
So adding a yellow 85b filter to the lens does exactly one thing--it removes the blue wavelengths, so now the light hitting the blue CCD is getting filtered twice--once when it's split or filtered internally and prior to that when it's getting cut out by the 85b filter. So you end up with a net loss of photons hitting the blue CCD. And the filter can't increase the light hitting the green and blue CCDs--because filters only remove light, they can't add light.
So adding a yellow 85b filter to the lens does exactly one thing--it removes the blue wavelengths, so now the light hitting the blue CCD is getting filtered twice--once when it's split or filtered internally and prior to that when it's getting cut out by the 85b filter. So you end up with a net loss of photons hitting the blue CCD. And the filter can't increase the light hitting the green and blue CCDs--because filters only remove light, they can't add light.
khmuse said:
GenJerDan
Veteran
Ah. Google is your friend..it lets you searchj for 85B. 
Here're the posts that prompted me to shop for an 85B:
Title: Re: white balance...
Post by David Jimerson on Sep 14th, 2004, 9:03am
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The DVX has more noise in the blue channel. Why? Not even Barry Green knows . . .
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Title: Re: white balance...
Post by Salvador on Sep 14th, 2004, 11:29am
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Image get's noiser when white balance is towards the 5600K end.
What I generally do is use the 3200K preset and a 85B filter.
Blue channel is always the noisiest when dealing with video.
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Title: Re: white balance...
Post by andre on Sep 15th, 2004, 2:23am
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The spectral sensitivity curve of CCD imagers shows significantly lower QE for the bleu spectrum part. So more gain is needed (=more noise) to get a balanced white (and colors). A 3200K reduces the noisy blue gain and makes the noise less visible.
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Title: Re: white balance...
Post by J_Barnes on Sep 15th, 2004, 5:35am
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Also, there seems to be a lot of noise in the blue channel of any image that undergoes compression. Take a look at a digicam blue channel in a raw or tiff file and then the same channel after a "maximum quality" JPEG compression...it's noise city!
Dan
Here're the posts that prompted me to shop for an 85B:Title: Re: white balance...
Post by David Jimerson on Sep 14th, 2004, 9:03am
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The DVX has more noise in the blue channel. Why? Not even Barry Green knows . . .
--------------------------------------------------------------------------------
Title: Re: white balance...
Post by Salvador on Sep 14th, 2004, 11:29am
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Image get's noiser when white balance is towards the 5600K end.
What I generally do is use the 3200K preset and a 85B filter.
Blue channel is always the noisiest when dealing with video.
--------------------------------------------------------------------------------
Title: Re: white balance...
Post by andre on Sep 15th, 2004, 2:23am
--------------------------------------------------------------------------------
The spectral sensitivity curve of CCD imagers shows significantly lower QE for the bleu spectrum part. So more gain is needed (=more noise) to get a balanced white (and colors). A 3200K reduces the noisy blue gain and makes the noise less visible.
--------------------------------------------------------------------------------
Title: Re: white balance...
Post by J_Barnes on Sep 15th, 2004, 5:35am
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Also, there seems to be a lot of noise in the blue channel of any image that undergoes compression. Take a look at a digicam blue channel in a raw or tiff file and then the same channel after a "maximum quality" JPEG compression...it's noise city!
Dan
Dan--I think those posts show some understanding that the blue channel is the noisiest, but a complete lack of understanding of how white balance works and the fundamentals of additive and subtractive color as applied to 3-chip digital cameras.
The underlying issue is that the lower sensitivity of CCDs in the blue part of the spectrum causes a lower signal-to-noise ratio in the blue channel. There's just less signal there. The solution is NOT to add an 85b filter that further reduces the light hitting the blue CCD. An 85b filter that removes some of the blue part of the spectrum will end up making the blue channel noisier.
Have I driven a stake through the heart of this myth yet?
The underlying issue is that the lower sensitivity of CCDs in the blue part of the spectrum causes a lower signal-to-noise ratio in the blue channel. There's just less signal there. The solution is NOT to add an 85b filter that further reduces the light hitting the blue CCD. An 85b filter that removes some of the blue part of the spectrum will end up making the blue channel noisier.
Have I driven a stake through the heart of this myth yet?
khmuse
Tech Guru
In response to Barry's reply, let me clarify my point. It is obvious that an optical filter is a subtractive (specifically spectrally selective) device and can not add to the energy levels presented to the CCD. It is also equally obvious that a 3 CCD camera utilizes a beam splitter and filtration (specifically band pass filters) with each sensor array. That stated I suggested considering the non-linear aspect of the CCD which remains unaddressed.
If this were purely a signal to noise issue, then any filtration, or anything which resulted in needing additional gain (or relative gain, one color channel to another), would diminish the performance as the signal level arriving at the CCD would be reduced. However, I suspect that this is a problem upstream of the quantizer (analog to digital converter) specifically, the CCD itself. I too have seen behavior in the blue channel that indicates that exposure to extremely high signal levels at very short wavelengths result in unusual noise behavior. Where this may be coming from is outside of the visual portion of the spectrum, likely well below 400 nm wavelengths. The generic graph that Barry provided shows no sensitivity information outside of the visible spectrum and is not really illustrative of my point. It is the out of band performance of the blue channel that may be enhanced by the use of spectrally limited energy that results from using an 85B filter in very high color temperature conditions.
There are two areas that could contribute to the effect mentioned. One is the non-linear nature of the CCD in response to very short wave length energy at high levels. This could aliases into noise (much like analog impulse noise) and give rise to the perceived performance improvement that was mentioned by GenJerDan. The other area that may be of interest is the internal filtration used within cameras like the 100. I could easily imagine that there could be a peak or number of peaks that appear outside of the intended pass band of the filter. In personal experience at the company that I work for, we use a fairly dark blue filter manufactured of cast acrylic in front of the IR detectors we use for remote control receivers. This might seem contradictory as one would think that IR acceptance would best be served by a filter that is red in appearance, however, when characterizing the spectral performance of materials, we discovered that there is a large reduction in the optical attenuation around 870 nm, just about where our IR transmitter is centered.
As stated in my first post on this thread, the performance advantage gained by optimizing the color temperature may be small, but might yet be something that is real. It could easily be that the reported performance enhancement seen when using warming filters with very high color temperature conditions, especially at high levels (as could easily be the case out doors on a very bright day) are the result of the out of band characteristics of the camera and/or non-linear response of the CCD. Similar conditions exists in chemical film cameras, hence the generally accepted practice of using a UV filter (for more than just a protective device to protect the front element).
Time allowing, I will obtain a UV source and see what the actual performance characteristics of the 100 are under these conditions. Anyone else have an interest in this subject?
If this were purely a signal to noise issue, then any filtration, or anything which resulted in needing additional gain (or relative gain, one color channel to another), would diminish the performance as the signal level arriving at the CCD would be reduced. However, I suspect that this is a problem upstream of the quantizer (analog to digital converter) specifically, the CCD itself. I too have seen behavior in the blue channel that indicates that exposure to extremely high signal levels at very short wavelengths result in unusual noise behavior. Where this may be coming from is outside of the visual portion of the spectrum, likely well below 400 nm wavelengths. The generic graph that Barry provided shows no sensitivity information outside of the visible spectrum and is not really illustrative of my point. It is the out of band performance of the blue channel that may be enhanced by the use of spectrally limited energy that results from using an 85B filter in very high color temperature conditions.
There are two areas that could contribute to the effect mentioned. One is the non-linear nature of the CCD in response to very short wave length energy at high levels. This could aliases into noise (much like analog impulse noise) and give rise to the perceived performance improvement that was mentioned by GenJerDan. The other area that may be of interest is the internal filtration used within cameras like the 100. I could easily imagine that there could be a peak or number of peaks that appear outside of the intended pass band of the filter. In personal experience at the company that I work for, we use a fairly dark blue filter manufactured of cast acrylic in front of the IR detectors we use for remote control receivers. This might seem contradictory as one would think that IR acceptance would best be served by a filter that is red in appearance, however, when characterizing the spectral performance of materials, we discovered that there is a large reduction in the optical attenuation around 870 nm, just about where our IR transmitter is centered.
As stated in my first post on this thread, the performance advantage gained by optimizing the color temperature may be small, but might yet be something that is real. It could easily be that the reported performance enhancement seen when using warming filters with very high color temperature conditions, especially at high levels (as could easily be the case out doors on a very bright day) are the result of the out of band characteristics of the camera and/or non-linear response of the CCD. Similar conditions exists in chemical film cameras, hence the generally accepted practice of using a UV filter (for more than just a protective device to protect the front element).
Time allowing, I will obtain a UV source and see what the actual performance characteristics of the 100 are under these conditions. Anyone else have an interest in this subject?
I don't get why people cling to this misconception in the face of any evidence. You're coming up with a tenuous explanation to prove an unsupported point. Occam's razor, my friend--the simplest explanations are the best. Blue filtered CCD sensors have more noise because CCDs have less sensitivity to blue light. Not because of an overload of UV light. If you want to do a relevant experiment, try shooting under low levels of 5500K light (say a Kino dimmed down) with the camera balance set to 5500K and with the balance set to 3200K + an 85b filter. Then do some frame grabs and compare the noise levels in the blue channel. So actually demonstrate that there *is* an effect before trying to explain it.
khmuse
Tech Guru
Thanks for the comment Barry, however the test at 5500K would not be useful to test the point that I was trying to make. I am specifically referring to conditions much above 5500K (like could be present in daylight conditions). I am certain that you are correct about in band conditions (2500K to 6000K) as they relate to the reduced sensitivity of the CCD in the blue portion of the spectrum, any filtration used here would increase the noise characteristics as a result of the simple reduction of the signal.
I too typically subscribe to Occam's razor, but am not always willing to dismiss out of hand empirical perceptions. There can be an underlying phenomena, though usually poorly attributed, present. Too often I have dismissed comments from those less technical only later to learn that there was something more than the ramblings of the unwashed masses.
As you suggest, I will conduct a test and if there is any evidence to support the theory I will post the results. My reason for my post here was to see if anyone present on this board had any similar experience or information to contribute and to possibly explain the reported perceived benefit. Specifically, I had hopped to see if there was any information as to the comparative attenuation of UV for both a standard UV filter and perhaps an 85B? It could turn out that in some situations an 85B is better than no filter, but a UV filter might have been just as or even more effective in that same situation. My post was not intended to be purely confrontational; rather it is just in my nature as an engineer and researcher to question everything until fully quantified.
I hope that no toes were stepped on too badly; in general I enjoy this board and its contributions. I suspect that you may have accomplished the goal of driving a stake into the heart of this!
I too typically subscribe to Occam's razor, but am not always willing to dismiss out of hand empirical perceptions. There can be an underlying phenomena, though usually poorly attributed, present. Too often I have dismissed comments from those less technical only later to learn that there was something more than the ramblings of the unwashed masses.
As you suggest, I will conduct a test and if there is any evidence to support the theory I will post the results. My reason for my post here was to see if anyone present on this board had any similar experience or information to contribute and to possibly explain the reported perceived benefit. Specifically, I had hopped to see if there was any information as to the comparative attenuation of UV for both a standard UV filter and perhaps an 85B? It could turn out that in some situations an 85B is better than no filter, but a UV filter might have been just as or even more effective in that same situation. My post was not intended to be purely confrontational; rather it is just in my nature as an engineer and researcher to question everything until fully quantified.
I hope that no toes were stepped on too badly; in general I enjoy this board and its contributions. I suspect that you may have accomplished the goal of driving a stake into the heart of this!
Barry_Green
Moderator
I first heard of this concept from Michael Phillips a couple of years ago. He said that CCDs are natively tungsten-balanced, and that you can get slightly better performance under daylight conditions by using the tungsten preset and an 85B filter.
Sounded preposterous, I've never seen anyone do that, etc... but... hey, how hard is it to test? So I tested it. And, indeed, to my eye, there is a little less noise in the overall picture when using tungsten balance and an 85b filter, as opposed to using the daylight preset.
Scharky posted a clip here not too long ago that showed the difference as well. It was a few months ago.
It's not a night-and-day difference, but it's enough of a difference that you can actually notice it, especially when you zoom in.
I don't know whether the overall image quality would be perceived as "better" -- adding another element in the optical path usually involves some sort of signal degradation -- but it can be demonstrated that whether it's "better" or not, the image is a little less noisy.
Sounded preposterous, I've never seen anyone do that, etc... but... hey, how hard is it to test? So I tested it. And, indeed, to my eye, there is a little less noise in the overall picture when using tungsten balance and an 85b filter, as opposed to using the daylight preset.
Scharky posted a clip here not too long ago that showed the difference as well. It was a few months ago.
It's not a night-and-day difference, but it's enough of a difference that you can actually notice it, especially when you zoom in.
I don't know whether the overall image quality would be perceived as "better" -- adding another element in the optical path usually involves some sort of signal degradation -- but it can be demonstrated that whether it's "better" or not, the image is a little less noisy.
Hmm. somehow I missed that clip, but I'd love to see some actual evidence. Maybe I'll run some tests myself, because the whole thing has always sounded like advice left over from the days of analog video cameras, but it doesn't make sense on the face of it.
khmuse: maybe there's something to your UV effect-- but I need to see more than anecdotal evidence that the effect is real.
khmuse: maybe there's something to your UV effect-- but I need to see more than anecdotal evidence that the effect is real.
scharky
Veteran
Ok, ok, let me did it up. Both Barry's, I don't claim to know what the hell I'm talkikng about, but I heard the "myth" as well, so I tried it out, and low and behold, less noise using the 85b filter. Is it worth having to cary the 85b around at all times. No, however I have found a few situations where I noticed a tad bit more noise during daylight situations that were minimized with the 85b filter. Do I know why, Barry_S has kinda prooven that I don't, but all I know is it seems to work.
Ok, let me dig it up. Just one second.
Ok, let me dig it up. Just one second.
scharky
Veteran
ok. here it is
http://www.stefweb.net/noisetest.mov
by the way, it is pretty big for such a short clip, about 15mb, I didn't want to introduce artifacts. To me the noise difference isn't huge, but seems most prevelent in the 13-20ire range. The video has been blown up about 200%, just to let you know. Again, not a technition here, just film student who cares about the details. To me it looks better, more of an overall less noisy look.
http://www.stefweb.net/noisetest.mov
by the way, it is pretty big for such a short clip, about 15mb, I didn't want to introduce artifacts. To me the noise difference isn't huge, but seems most prevelent in the 13-20ire range. The video has been blown up about 200%, just to let you know. Again, not a technition here, just film student who cares about the details. To me it looks better, more of an overall less noisy look.
khmuse
Tech Guru
Before I proceed with the UV theory test, I wanted to get the opinion of Barry_S as to the procedure that I propose and its validity. What I plan to due is to expose an 18% gray card to a fairly strong UV source that we have here in our lab (its output is centered around 3000 angstrom or 300 nm). The perception looking at the otherwise un-illuminated gray card will be that it is nearly absolute black. A DVX100A that we have here in our lab will be focused on the gray card and I will prevent any visible light sources from illuminating the surface. What I intend to do is look at the blue channels output (both as recorded and at the quantizer within the 100) to see which pixels are active and at what magnitude. Then I will insert both a conventional UV filter and an 85B filter to see which, if either, has any effect on the blue channel (or CCD). The result should be both illustrative of my hypothesis and more importantly reproducible. The only thing that I currently don't have is access to an illumination meter that is calibrated into the UV region. I suspect that there are some occupational exposure instruments that might have traceable certifications that are designed to work in this region, but I may have to rely upon UV source’s manufactures data to quantify the illumination levels.
Does this seem to be an acceptable methodology to Barry_S or anyone else who would care to comment?
Does this seem to be an acceptable methodology to Barry_S or anyone else who would care to comment?