Calibration questions

[Pecker]

Okay, I want to open up a discussion here, but I'd like to keep it civil.

I'm extremely open to all opinions, and would like to hear from people with their own points of view, particularly our resident experts, who know more about this then I.

I recently purchased (or my school did) an Optoma HD65 for my school.

On setting it up I went to the HD65 owners thread at these forums, and used the settings recommended there.

Having tried these, the picture looked great. Also, when I tried the red, green and blue filters with my DVE Blu-ray Disc, they all looked spot on, or at least very close.

Now my understanding is that this is either impossible or extreme luck bordering on the miraculous.

Time and time again I've read that using someone else's calibration settings are 'useless', as manufacturing tolerances mean that no two projectors will be alike (let alone the different sources probably used for the DVE disc). Neil Davidson (a real forum guru, and an expert with many years' experience in this field) has described the filters as 'worthless'.

If the filters are inaccurate, even if my settings were correct, they'd look wrong through the filters.

The only way the DVE colour bars should look correct (as they do) is one of the two ways:

1 - I'm the luckiest man alive, and by pure chance the settings I input just happened to be right for my player/PJ combination, and I got one of the few accurate sets of filters.

2 - My settings are out and my filters are inaccurate, but due to a bizarre coincidence (running at lottery-winning improbability) the two are out in exactly equal but opposite directions, culminating with the colour bars looking correct, when in fact they're not.

Now there is a third option, which I'm currently tempted to believe, but I'm most certainly open to persuasion that this is wrong.

3 - Modern manufacturing tolerances are pretty decent, and whilst one HD65's components may differ slightly from the next, they're never going to be far away. Meanwhile, whilst Joe Kane cannot guarantee his filters will be spot on, they're all going to be pretty close. Subsequently, it would appear that using someone else's calibration settings may not be perfect, but it gets you a long way there.

There will be caveats to this. For example, if your PJ manufacturer switches supplier for a particular component, there may be a sudden change in the settings needed. Also, room environment may impact on the colour of your picture.

Comments?

In general, I'd like to know how I appear to have such good result looking at DVE colour bars through the filters.

Steve W

[Phil Hinton]

Originally Posted by Pecker

Okay, I want to open up a discussion here, but I'd like to keep it civil.

I'm extremely open to all opinions, and would like to hear from people with their own points of view, particularly our resident experts, who know more about this then I.

I recently purchased (or my school did) an Optoma HD65 for my school.

On setting it up I went to the HD65 owners thread at these forums, and used the settings recommended there.

Having tried these, the picture looked great. Also, when I tried the red, green and blue filters with my DVE Blu-ray Disc, they all looked spot on, or at least very close.

Now my understanding is that this is either impossible or extreme luck bordering on the miraculous.

Time and time again I've read that using someone else's calibration settings are 'useless', as manufacturing tolerances mean that no two projectors will be alike (let alone the different sources probably used for the DVE disc). Neil Davidson (a real forum guru, and an expert with many years' experience in this field) has described the filters as 'worthless'.

If the filters are inaccurate, even if my settings were correct, they'd look wrong through the filters.

The only way the DVE colour bars should look correct (as they do) is one of the two ways:

1 - I'm the luckiest man alive, and by pure chance the settings I input just happened to be right for my player/PJ combination, and I got one of the few accurate sets of filters.

2 - My settings are out and my filters are inaccurate, but due to a bizarre coincidence (running at lottery-winning improbability) the two are out in exactly equal but opposite directions, culminating with the colour bars looking correct, when in fact they're not.

Now there is a third option, which I'm currently tempted to believe, but I'm most certainly open to persuasion that this is wrong.

3 - Modern manufacturing tolerances are pretty decent, and whilst one HD65's components may differ slightly from the next, they're never going to be far away. Meanwhile, whilst Joe Kane cannot guarantee his filters will be spot on, they're all going to be pretty close. Subsequently, it would appear that using someone else's calibration settings may not be perfect, but it gets you a long way there.

There will be caveats to this. For example, if your PJ manufacturer switches supplier for a particular component, there may be a sudden change in the settings needed. Also, room environment may impact on the colour of your picture.

Comments?

In general, I'd like to know how I appear to have such good result looking at DVE colour bars through the filters.

Steve W

Ok, good subject to cover and one where there is still a lot of misunderstanding and bad advice. So let’s start by clarifying what you are asking.

The word Calibration is in my opinion is over used and abused. So lets set some rules here. What you are describing is not technically calibration as you are not using any standard reference point or doing anything other than using the front panel controls on the device.
So lets think of the subject in two parts, basic set up and calibration.

Basic set up.

This involves using a set up disc such as DVE or the many other pattern discs out there.
The objective is to set the front panel controls (Brightness, Contrast, Sharpness, Colour and other user controls). Let’s get one thing very clear. This kind of set up is somewhat subjective unless you use measuring devices and software. You are setting the basic controls to improve the image but you are not actually measuring or changing the underlying aspects of the devices colour or greyscale performance, it is impossible to do this by eye. So what you are doing in a basic set up is improving the set image produced by the display, but you are not changing the underlying colour or greyscale performance. So it’s not a calibration because you are not measuring or aiming for a standard or reference point.

Calibration

In my opinion, Calibration is where you use a reference point and actually measure and correct to that standard. The obvious standards to choose are ITU-R BT709 (Rec 709) and/or SMPTE-C. Now that you have a standard to work to you will require software and a fairly accurate meter. You will also need a display device that has some control over the greyscale (White Balance) and colour points (Colour management System). Not all devices have both of these. The basic set up is used before you then measure and correct using software, a meter, and experience to correct the image to the standard you are aiming for. There are very few domestic displays that get 100% accurate (indeed there are also many pro devices the same). That is why we use error points like Delta E equations to help with calibration results against human vision seeing these. In most cases you can have a few errors in the measurements and not see those by eye. However, it still requires software and meter readings to dial the settings in so the errors are not seen. You cannot set greyscale or colour points by eye and get anywhere close to accurate. It also depends on the software and meter used as to just how accurate you get the final image.

Now let’s talk filters.

As you can see getting a displays colour correct is impossible by eye and you generally don't use the colour control for correction of them. Confused?
The colour points in the Rec 709 points (assuming the display gets anywhere close to that standard out of the box) can be moved by the colour control in the main menus, but to detrimental effect. They are all moved together but not equally and depending on the colour decoder in the display, will start causing severe errors very quickly. So you don't use the colour control to correct any colour points, that's not what it is really designed to do. I very rarely find that I move the control very much in a pro calibration. It is for trying to balance the saturation (Luminance) of all the primary colours and that is why the filters were invented. This is supposed to help you balance the three points so that you reach a compromise across all three. However the main problem is that how can that blue filter be the same as the blue energy of different displays? It can't! So use of the filter is very much just a guide and depending on the quality of the display you could end up with some pretty extreme results by eye even though it looks right with the filter. The filter is not accurate and is not a standard to trust. Even if it looks ok by eye. I have also found that the filters start to change colour over a few months when left in my bag or the disc box.

So are tolerances really an issue? Well for basic set up you could copy someone else’s settings and to your eye it might look good. This is however very much a personal preference and not using any standards. And that’s front panel settings, not greyscale or cms. There is however so many sources that can change the way a display will look other than tolerances as well. Environment is a key one. The colours of your walls, the level of ambient light, screen surface (for projection), throw ratio, bulb life, and quality of the device. Then you have variances in sources used. And then you have slight variances between the same models of display. The variances in displays will be more profound when doing a basic set up as it will all depend on how well it is set up to display an image when soaked and calibrated in the factory. This is usually done quickly on a production line, so it is the law of averages that you will get slight differences. This is not as big a deal as the other points above, but will affect things.
I have hundreds of hours now of measuring and testing products to confidently say that using other peoples settings is inaccurate and will very rarely get you close to what the other display is doing to what your display is doing. And if this is by eye then that is two fold. How do you know that what you are seeing is the same as the person who gave you the settings is seeing? Impossible unless you have them side by side and then of course you change the goal posts again in the points of environment and so on.

The whole point of calibration is to match the same standards that are used in the transfer and distribution of content in 8 bit video. The major point is how accurate is your projector to start with for colour points and greyscale. If it’s out, and in my experience it most certainly will be, then front panel controls and test discs can only really set up brightness, contrast and sharpness by eye. It's only when you measure and have the ability to correct can you then get close to being accurate to the reference point you are aiming for. And, of course, you are also correcting the image to the environment, screen surface and so on. If that is to see material on 8 bit video as intended when it’s mastered via the standard approach used in film and TV, then you really need to have software and a fairly accurate meter to achieve that. I have seen differences with the same products side by side in the same room, so, it’s impossible to state as fact that tolerances do not exist, when the experience says otherwise.

The most important FACT to come from the ever growing conversations about swapping settings is that people want the best picture possible from their display. So they are taking them out of the factory preset Vivid, Dynamic and standard modes and actually trying to get close to seeing material as it should be seen. That is encouraging along with the manufacturer’s actually now taking notice that we don't want 9300k white levels and want to see material correctly. The introduction of the THX preset has gone a long way to getting the colour points and greyscale as close as possible to the standards. With the introduction of cheaper solutions for accurate calibration and hopefully training classes for more and more enthusiasts, we might one day get close to having displays that get the reference points fairly correct and it just needs slight tweaking by the end user.

But again, be clear in what you are doing. Using filters and a picture looking great is fine for personal preference. If you want accuracy - and as a big film nut, like you are - the only way you are going to get close to the image being correct to the standards is to calibrate correctly using the right equipment.

[Neil Davidson]

Guys,

Phil has posted up an excellent response so there is not a massive amount for me to add. I will just specifically touch on the subject of filters which has come up a couple of times lately.

Colour filters should only be used with a colour bars pattern to compare the relative luminance of the individual primary colours with their relative luminance in white and the relevant secondary colours.

If you find that the primary colour bar is brighter than the white segment viewed through a filter then it indicates that the colour decoding function in the display is out of balance and pushing the primary more than it should be.

The problems with filters begin when you start looking at how the luminance is made up on the display. I am sure that anyone interested in calibration will be familiar with the formula

Y = 0.2126 R + 0.7152 G + 0.0722 B

This shows how the luminance of HDTV white is created by the contribution of each primary. Now this formula is only valid if the red green and blue primaries are perfect in xyY. Now as we know even the world's best calibrator can't get close to this situation on most displays. Even P7 based DLP projectors have error of 1-2dE on primaries.

For PAL which is almost identical to HDTV in terms of colour coordinates:

Y = 0.2220 R + 0.7066 G + 0.0713 B

You can see that this is quite different than HDTV despite the closeness in primaries. This formula is utterly dependent on the measured colour primaries on the display. In systems with a CMS this means that it is varying all the time as the calibration is dialled in. Even when you are finished you only need to look at the range of results in the AVForums reviews to see that these never really come close enough to the standard to work with a perfect set of filters.

Now we can hopefully understand why filters are pointless on most displays - the primaries are so far from standard that the maths make it impossible for well designed filters to give reliable data.

There are other problems using filters with DLP projectors. In particular BrilliantColor which boosts image brightness by having extra sections on the colorwheel totally ruins these equations and again does not work with filters.

Hope this clarifies things

[Pecker]

Originally Posted by Neil Davidson

I am sure that anyone interested in calibration will be familiar with the formula

Y = 0.2126 R + 0.7152 G + 0.0722 B

In Huddersfield we talk of little else.





Seriously, a big thanks to Phil & Neil for some typically detailed and comprehensive answers.

If I say the responses raise more questions than answers, I hope you do not take that as a criticism of your comments, but rather an acknowledgement of the complexity of the subject. Thanks again.

So, a quick question - answers in as layman's terms as possible:

I could have left everything set to '0'. If I do this, all the colour bars are out.

Instead, I've entered these figures, and all the colour bars are now spot on (or bloomin' near).

Have I done any good?

Steve W

ps I'm hoping the training days still happen...preferably during the Summer holidays.

SW

[Pecker]

Originally Posted by Phil Hinton

But again, be clear in what you are doing. Using filters and a picture looking great is fine for personal preference. If you want accuracy - and as a big film nut, like you are - the only way you are going to get close to the image being correct to the standards is to calibrate correctly using the right equipment.

Phil, I just thought I'd pick up on this, if you don't mind.

RE:

Originally Posted by Phil Hinton

But again, be clear in what you are doing. Using filters and a picture looking great is fine for personal preference.

Firstly, I have never said and do not believe either that calibration (on any level) should be done by eye, nor that it is ever a matter of personal taste. The correct colour temperature, etc, is the correct colour temperature, and if someone prefers the 'wrong' settings then, whilst that's up to them, it's not what we're aiming for here. I hope you understand that we're in complete agreement on that. The human eye is absolutely not an accurate measure for these settings.

RE:

Originally Posted by Phil Hinton

If you want accuracy - and as a big film nut, like you are - the only way you are going to get close to the image being correct to the standards is to calibrate correctly using the right equipment.

Secondly, I agree with the general comment, but with a caveat. I want my films to look as close as possible to how the director intended. If the original camera negative could be run through a multi-million dollar convertor and piped straight into me brain, then I want that.

But all of this has a cost, and in all areas of home cinema we need to balance cost with effect. In other words, yes it makes a difference, but how much is that difference worth in £GB?

Just because someone is happy with their picture (whilst accepting it could be better) doesn't mean they're not a film nut.

Just as an example, some projectors and TVs now have THX modes, and from your test results they look to be very good, whilst not being perfect. Compared to a display without those pre-sets, they appear to get you 90% of the way there. Now if your display doesn't have those modes you need to balance the £250 (or whatever) vs the 100% improvement. If the display has those modes you need to balance the same money against only a tenth of the improvement.

I personally don't feel the argument should ever be "It's better, so you must have it" - there must always be an element of weighing up the cost vs the improvement.

Great discussion.

Steve W

[Phil Hinton]

Originally Posted by Pecker

Phil, I just thought I'd pick up on this, if you don't mind.

RE:



Firstly, I have never said and do not believe either that calibration (on any level) should be done by eye, nor that it is ever a matter of personal taste. The correct colour temperature, etc, is the correct colour temperature, and if someone prefers the 'wrong' settings then, whilst that's up to them, it's not what we're aiming for here. I hope you understand that we're in complete agreement on that. The human eye is absolutely not an accurate measure for these settings.

RE:



Secondly, I agree with the general comment, but with a caveat. I want my films to look as close as possible to how the director intended. If the original camera negative could be run through a multi-million dollar convertor and piped straight into me brain, then I want that.

But all of this has a cost, and in all areas of home cinema we need to balance cost with effect. In other words, yes it makes a difference, but how much is that difference worth in £GB?

Just because someone is happy with their picture (whilst accepting it could be better) doesn't mean they're not a film nut.

Just as an example, some projectors and TVs now have THX modes, and from your test results they look to be very good, whilst not being perfect. Compared to a display without those pre-sets, they appear to get you 90% of the way there. Now if your display doesn't have those modes you need to balance the £250 (or whatever) vs the 100% improvement. If the display has those modes you need to balance the same money against only a tenth of the improvement.

I personally don't feel the argument should ever be "It's better, so you must have it" - there must always be an element of weighing up the cost vs the improvement.

Great discussion.

Steve W

Yes, it costs money to get a professional in to do it. And we will never get to a stage where manufacturers get it spot on as there are 'other' complex issues to take into account as well. BUT, things are moving in the right direction and the fact that we are now seeing manufacturers taking the subject seriously (and asking us to help in some quarters), can only bode well for the future products.
The main issue is still a matter of personal preference over reference, and it will continue to be the case that the general public, enthusiasts and even professionals including manufacturers need some degree of education on the subject. Its all good and well releasing products with 160% of the HDTV colour space, but you have to ask why? and Digital cinema colour or xvcolour? All that is doing is adding things that are not there into the image and as a film and TV fan, I don't need extra saturation of colours, I want it as it was mastered.
The 'what the director intended' comments also get misused and are open to abuse (not talking about you here, general comment). We all know the issues very well about what the director signed off on. BUT, if we are getting an approved print from the film studio or director or cinematographer etc on 8 bit video, you can only see that as it was mastered on a calibrated display that matches the standards use to transfer it to video. The arguements that actually the director didn't intend something that ends up on disc is actually irrelevent when talking about calibration. You are still seeing what was mastered at the right levels on a calibrated system, whether its actually what the director intended is a point of arguement for the studio, director and film fans. Hopefully that aspect is now pretty obvious to bear in mind.

[Pecker]

Originally Posted by Phil Hinton

The 'what the director intended' comments also get misused and are open to abuse (not talking about you here, general comment). We all know the issues very well about what the director signed off on. BUT, if we are getting an approved print from the film studio or director or cinematographer etc on 8 bit video, you can only see that as it was mastered on a calibrated display that matches the standards use to transfer it to video. The arguements that actually the director didn't intend something that ends up on disc is actually irrelevent when talking about calibration. You are still seeing what was mastered at the right levels on a calibrated system, whether its actually what the director intended is a point of arguement for the studio, director and film fans. Hopefully that aspect is now pretty obvious to bear in mind.

Again, i fundamentally agree. The only way to get what's on the disc 100% accurately is a 100% accurately calibrated display.

But again it comes down to %ages. May I give an example? You've previously said that watching a film on an uncalibrated display was like listening to a 33.3 rppm record at 78rpm - a calculated overstatement, for sure.

Well, I'm sure we'd all agree that the record should be listened to at 33.3. But if we can get a record player that runs at a steady speed, but that maybe anywhere between 33 and 33.6, then is that good enough, or is it worth £200+ to get it right?

What about between 33.2 & 33.4? Or 33.29 and 33.31?

Accuracy is good. How accurate do you need to be before it's no longer worth a few hundred pounds for the next 10%, 1% or 0.1%, is what is open to debate.

Now, back to your original point about what's on the disc. If your display is (for the sake of argument) 5% out, but what the director wants and what is on the disc is usually 10% out, then getting rid of that final 5% error on your display becomes less worth it, though even then I wouldn't argue it's not worth doing at all.

Sorry, I think we've gone a little off topic. Back to my question in post #4:

So, a quick question - answers in as layman's terms as possible:

I could have left everything set to '0'. If I do this, all the colour bars are out.

Instead, I've entered these figures, and all the colour bars are now spot on (or bloomin' near).

Have I done any good?

Steve W

[Phil Hinton]

Originally Posted by Pecker

Now, back to your original point about what's on the disc. If your display is (for the sake of argument) 5% out, but what the director wants and what is on the disc is usually 10% out, then getting rid of that final 5% error on your display becomes less worth it, though even then I wouldn't argue it's not worth doing at all.

Sorry, I think we've gone a little off topic. Back to my question in post #4:



Steve W

That analogy doesn't really work, as if the calibration is as accurate as possible, you are seeing what was mastered. Period. If the print is wrong and the master wrong, it's wrong on the calibrated display as that is what is mastered. What you are not doing is adding in errors on a large scale by watching on a display that is not calibrated. As the director films on...film....we will never get to see exactly what he wanted anyway, as video at the moment (and for the forseeable) is 8 bit. As the delivery system is less for colour etc, it is mastered to give as close as possible to what was on the film. Even on a calibrated display you can only see what is mastered. Its the best we have and will be for some time. Watching a film on 8 bit video on a display that has not had its greyscale corrected or its colour points done, you are adding in what was not there. So you are adding in saturation that shouldn't be there and changing the intended look. Once a display is calibrated for video, you do not have to change settings for any material, no matter how that was filmed, as it will always be mastered for video the same way, so you see it as so.

Question 4.

Have you tried moving the controls about when using the filter or just at the point you were given? If it just happened that the given point works for you and other settings are wrong, then that is what I would describe as a co-incidence?
Hope that helps.

[Neil Davidson]

Originally Posted by Pecker

So, a quick question - answers in as layman's terms as possible:

I could have left everything set to '0'. If I do this, all the colour bars are out.

Instead, I've entered these figures, and all the colour bars are now spot on (or bloomin' near).

Have I done any good?

The short answer is...maybe

Without seeing the resulting image it is impossible for me to answer this question as I can't tell if the colour is over or under saturated (as in the luminance is too high per the adjustment of the colour control - holy confusing nomenclature!). My preference for setting this control when I can't measure or do a blue screen only is to use a known scene or even better, a static image. I have a few scenes that I have seen so often that I simply know what they should look like now and can tell pretty quickly what is wrong in the setup from looking at them.

I have to throw it back to you then - does the image look right to you?

[Pecker]

Originally Posted by Neil Davidson

The short answer is...maybe

Without seeing the resulting image it is impossible for me to answer this question as I can't tell if the colour is over or under saturated (as in the luminance is too high per the adjustment of the colour control - holy confusing nomenclature!). My preference for setting this control when I can't measure or do a blue screen only is to use a known scene or even better, a static image. I have a few scenes that I have seen so often that I simply know what they should look like now and can tell pretty quickly what is wrong in the setup from looking at them.

I have to throw it back to you then - does the image look right to you?

Yes...but.

Yes, but the image on most decent displays looks pretty good to me. This one looks...different. Better? Well, I really need to do a lot more viewing. Let's put it this way, it looks very good.

Unlike yourself and Phil, I don't have the same sort of invaluable experience, so I have no short list of scenes where I know exactly what something should look like.

Originally Posted by Phil Hinton

Have you tried moving the controls about when using the filter or just at the point you were given? If it just happened that the given point works for you and other settings are wrong, then that is what I would describe as a co-incidence?

I'll try moving the controls and let you know.

I'm of the same thinking of you - except that it'd be one hell of a coincidence.

Steve W

[KelvinS1965]

With a Lumagen VP it is possible in service mode to engage a setting where the VP itself only passes one colour giving the on screen result similar to holding a filter up. Is this method any more accurate than filters?

[Phil Hinton]

Originally Posted by KelvinS1965

With a Lumagen VP it is possible in service mode to engage a setting where the VP itself only passes one colour giving the on screen result similar to holding a filter up. Is this method any more accurate than filters?

There are a number of displays with this built in now. A good example is the new LG sets that have red, green and blue filters. If you do not have the ability to measure then using these would be more useful than a piece of coloured plastic. I would however be careful about where those filters are added within the display chain.

[Phil Hinton]

Originally Posted by Pecker

I'll try moving the controls and let you know.

I'm of the same thinking of you - except that it'd be one hell of a coincidence.

Steve W

Not really as it could be that the particular colour decoder works in a set manner that means it is very similar over a number of machines built, or even them all. Remember though that the filter is only really a guide.

[KelvinS1965]

Originally Posted by Phil Hinton

If you do not have the ability to measure then using these would be more useful than a piece of coloured plastic. I would however be careful about where those filters are added within the display chain.

I have got a sensor for measurement (I1-LT and HFCR), but lack of repeatablity meant that I have lost confidence in it. I may get an ISF calibration done at some point so this could be accademic, but thanks for the quick answer.

[Pecker]

Originally Posted by Phil Hinton

That analogy doesn't really work, as if the calibration is as accurate as possible, you are seeing what was mastered. Period. If the print is wrong and the master wrong, it's wrong on the calibrated display as that is what is mastered. What you are not doing is adding in errors on a large scale by watching on a display that is not calibrated.

It's my fault Phil, I'm not putting this very well.

Okay, let's try this. To further your 'record speed' analogy.

SCENARIO 1 - John Lennon is handed a first pressing of I Am the Walrus. He sticks it on his record player, and the player is spinning at 25rpm instead of 33.3. He says "This sounds way too slow!".

QUESTION 1 - Does he need his turntable calibrating? YES!

SCENARIO 2 (a) - John Lennon is handed a first pressing of I Am the Walrus. He sticks it on his record player, and the player is spinning at 33rpm instead of 33.3. He says "This sounds just right!".

QUESTION 2 (a) - Does he need his turntable calibrating? NO...or does he...

SCENARIO 2 (b) - John Lennon is handed a first pressing of I Am the Walrus. He sticks it on his record player, and the player is spinning at 33rpm instead of 33.3. He says "This sounds just right!". Paul, George and Ringo are sat there and say "Hold on, that sounds a little slow".

QUESTION 2 (b) - Does he need his turntable calibrating? That's up to John. Just to be clear, we're not talking about personal preference here. He knows what it should sound like, he just can't spot the difference because it's too small. The other three can. John might want to calibrate the turntable just to be sure he's getting exactly what's on the disc, but I think we'd probably agree it's not as much of a pressing issue.

Scenario 3 - John Lennon is handed a first AMERICAN pressing of I Am the Walrus. He sticks it on his record player, and the player is spinning at exactly 33.3. This is the same player he used to listen to the first UK pressing the week before. Unfortunately, due to an error at the pressing plant, the US version is running slightly slower - the equivalent of having his turntable run at 33 instead of 33.3. John can't tell the difference.

QUESTION 3 - If John can't tell the difference, should Beatles fan Fred Smith get his turntable calibrated to be more accurate than 0.3rpm out.

This is where we'll agree to differ, Phil. You would say always 'yes'. I'd say, when we get to margins that the director doesn't notice, you’re probably safe to leave things as they are.

Having said that, I take your point of view - it's just a matter of opinion. If I can get to the training sessions and ensure I know what I'm doing, I'll buy the necessary kit and calibrate as close as I can get.

Thanks for the chat. Any more news on those training sessions?

Steve W