Testing different prices HDMI cables. Suggestions welcome, results will be published here.

Hi,

A bit of background info. I recently bought a projector (Epsom 3500), screen and hdmi cable (16 meter). When demoing the setup I saw a distinct difference in picture quality of the two HDMI cables.

The common belief is that this is not possible. Some believe that HDMI being digital will either show a picture or not. This is not true. The picture is made up of a large amount of information, if some of the information is corrupted then the display device may try to correct it and still display the picture resulting in artifacts. If too much information is corrupted then you may loose the picture and sound.

The strange thing I found was that I saw a distinct difference in colour saturation and picture sharpness which I cannot explain. All logic specifies that this is not possible with HDMI but I saw what I saw so in an attempt to convince myself I am not mad I spoke to the shop I bought the cables from and asked if I could borrow the cheaper cable and test them both together at home.

Imagine my shock when they were very happy with the idea and have agreed to lend me a selection of 10->15 meter cables of different qualities and prices so i can do an independent test . Yep I was pretty surprised too but as one of their guys lives a few blocks away they can always come round with a baseball bat to get them back I guess.......

I am not an electrical engineer and so I do not have electrical testing equipment and the like so I propose to do a 'sight test'.

I have the following equipment (low to medium level so hopefully more relevent to most people rather than top end stuff);
Samsung BD-P1600 BluRay player.
A.C.Ryan HD Mini player (streaming from NAS PC via hardwired cat6 infrastructure).
Yamaha RX-V465 AV Amplifier.
Epson EH-TW3500 (believe it is the 8100 in the UK)
X-Box 360 Kinect.

I may also be able to get hold of my brother-in-laws PS3 (fat).

I will be using my source player to play a movie /game to a certain point in a dark room through the 3500 projector and then pause it. I will then take a snap with my Canon 5D (tripod mounted with a remote release). Same settings for each cable on everything (projector, player, camera). The snaps will be in CR2 format (i.e. raw) and I will make them available for anyone who wishes to view them.

If someone wants to make available a test file (non copyright material please) then I could maybe try that.

At best it will show any differences with the cables.

At worst it will give some home cinema pics to look at and prove me mad .

If anyone has any suggestions about what they would like tested or settings, games (XBox), movies (I have limited movies in HD but could provide a list).

Of course I have no links to cable manufacturers (financial or otherwise) or any retail shops and no vested interest in the outcome (save proving my sanity). There is enough info about me in the getting fit thread linked in my sig (must get back to updating that).

RB

Copied over from the other thread:

OK, so taking photos how do we know that,

- Your 5D is as good as it gets in terms of accuracy.
- The lens isn't skewing results.
- You are taking the best possible picture in the shop with the camera setup properly with the picture taken as best it can be.
- The lighting in the shop won't affect the picture.

Also, how well is your montior calibrated for viewing pictures and how can we all see the same thing when everyone has a different system, montior and settings

Finally, when it comes down to what you saw in the shop, how do we know you know what an accurate picture 'should look like' and that their av equipment and display was one of the best display capable of producing a truly accurate picture and was even calibrated properly? Also knowing which cable was installed at what point intoriduces the your mind and it's powers of perception based upon presumed quality vs price with branded cables.



Don't waste your time on this, it won't prove anything conclusive and there are far too many variables and questions with the methodololgy. Just watch those avforums videos, buy a cable that works then get on with enjoying using your system

As posted int he other thread...

Sorry, I have not explained it very well it seems.

It does not matter how good the camera is or how good the lens is or what the setup is (pretty good in my situation but that is immaterial). What matters is that all cables are tested in the same conditions with the same equipment as the aim after all is to compare the differences and not the overall fidelity. As far as monitor calibration and image capturing equipment goes that would apply to any test be it the one I am proposing or the ones on the AV forums which show images of the equipment connected to the cables.

I am interested in the results as they affect the picture quality I see with the equipment I have and not the results of an AV professional using equipment that is significantly more expensive or testing the signal quality of the cable alone without factoring in the source and destination affects.

Having the chance to test the cables would seem like a good thing to me. I am a bit confused that you seem to think it is not and are actively encouraging me not to make the effort.

RB

If you don't have colour calibration equipment, then it's dead in the water.

EVH said:

If you don't have colour calibration equipment, then it's dead in the water.

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Ok, I can see I am going to have problems with getting over what I can do and what I am willing to do.

I am not testing the colour fidelity of the projector or of the source or of the cables. I am interested to see if the pictures are different given the same source, destination and recording equipment (i.e. the camera). I appreciate it is not fully scientific and I have no intention for it to be. It is meant to be the comparison of using different cables against the baseline.

If for example one cable produces vibrant colours and another cable seems to produce muted colours and all other things are equal then it would seem reasonable to suggest the cable is causing the effect. The fact the colours are not perfect in the first place is neither here or there. The difference between cable a and cable b is the point.

I understand for people who take their home cinema and HiFi very seriously will have no interest in anything resulting from the tests I may perform. This is not intended for them. This is intended for people like me.

I appreciate I may be the only person like me here though .

It my be a good leverage point to see if the shop will calibrate the projector for me though .

TBH it may turn out there is really no difference at all and if that is the case then all well and good, I will still put the results up. People can see them and make their own choices.

Again one point I would like to make is that the shop supplying the cables is not asking for anything apart from a copy of the photos. They are not applying any pressure and if the cables all produce the same results then that is what they would get back.

I just, maybe mistakenly considering the replies so far, though some people may also be interested here.

Nevermind, take it or leave it. I will put anything I find here for others to make up their own mind.

RB

Yes, but if you took a colour meter reading off a display, and as the source has a PS3 with a test disc, swapped cables and took another reading you'll directly capture the variance of the cable, no? (as you're only changing 1 variable).

Obviously, this works if your display is ISF calibrated or you can verify that it's consistent at producing accurate colours.

I think it may have been mentioned in the other thread, but Digital Foundry already did something like this using proper equipment; they found no difference between any of the cables they tested. The only time a better cable will make a difference is over longer distances, which you've seen to be true already.

i think its a worthy excercise mate, and good on you! It wont please the purists, but if each cable should produce the same result (which is what people have said about digital signals) then only swapping them shouldn't make a difference - if it does, then there's some merit in the study. That said your kit needs to be consistent in its abilities to output the same at all times too, else thats a variable you wont be able to control. Might be worth doing a blind study (get a mate to change the cables around without telling you which) once you have weened it to down to a few - this way you wont be being ubjective.

I think the biggest issue you'll face though is in trying to capture any differences - and thats where it becmes a little anecdotal i guess, great for you, interesting for us but probably not that useful for the shop.

WOuld also be worth checking 3 different batches of the same cable - to see if changes between batches shows variance, at which point again whilst your test may be valid the results wont be transferrable.

Good luck!

Seems like a pointless test to me, without all the proper testing gear run under 'lab' conditions your results are void.

I've got quite a few HDMI leads, first one i ever got was a 2mtr monster cable cost about £70 3 years ago, the picture quality is no different from a £3 jobbo from eBay, the only variance is build quality.

TheVoice said:

I think it may have been mentioned in the other thread, but Digital Foundry already did something like this using proper equipment; they found no difference between any of the cables they tested. The only time a better cable will make a difference is over longer distances, which you've seen to be true already.

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Yes although they noted that the cables should produce the same picture up to 4 metres.

I have a projector and I am sure some others would like to move in that direction and with everyone telling them that all the cables are the same they may end up with a cable that is not that good (maybe borderline at that length) and will not find out until the cable is buried in their walls. The thing that most people seem to be ignoring (although not yourself) is that the cable can make a difference at longer lengths.

As per the other thread I saw differences that I am told could not possibly be there so I am going to take another look and see if I can see them again.

I thought recording the results may be of interest. Seems only the minority agree.

No problem, I will be testing anyway so if people believe there is no merit then they can just ignore.

RB

EVH said:

Yes, but if you took a colour meter reading off a display, and as the source has a PS3 with a test disc, swapped cables and took another reading you'll directly capture the variance of the cable, no? (as you're only changing 1 variable).

Obviously, this works if your display is ISF calibrated or you can verify that it's consistent at producing accurate colours.

Click to expand...

Yep I see where you are coming from and it would give hard and fast figures rather than just subjective pictures. I also appreciate that you are trying to help improve the method rather than repeating the mantra of 'no lab, no good' .

Not sure I can accommodate but will see. If the projector is calobrated then the histogram from the raw camera image can go someway towards showing differences.

I will have a think on any other ideas.

Thanks
RB

Pug said:

i think its a worthy excercise mate, and good on you! It wont please the purists, but if each cable should produce the same result (which is what people have said about digital signals) then only swapping them shouldn't make a difference - if it does, then there's some merit in the study. That said your kit needs to be consistent in its abilities to output the same at all times too, else thats a variable you wont be able to control. Might be worth doing a blind study (get a mate to change the cables around without telling you which) once you have weened it to down to a few - this way you wont be being ubjective.

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Thanks Pug.

Maybe I will get my son to grade the pictures and see if it matches my views. I will probably let a couple of friends from work take a look as well.

Pug said:

I think the biggest issue you'll face though is in trying to capture any differences - and thats where it becmes a little anecdotal i guess, great for you, interesting for us but probably not that useful for the shop.

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Hopefully the camera will be good enough with the long exposure. It is a full frame sensor and so a bit more resistant to 'noise' but I will see when I try.

Pug said:

WOuld also be worth checking 3 different batches of the same cable - to see if changes between batches shows variance, at which point again whilst your test may be valid the results wont be transferrable.

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A valid point but probably a little further than I am likely to go and am probably less likely to be able to pick up on batch differences unless on batch is noticeably faulty.

Cheers
RB

Firestar_3x said:

Seems like a pointless test to me, without all the proper testing gear run under 'lab' conditions your results are void.

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Yeah, you see, I don't live in a lab so lab results don't have much bearing in my real world life where the variables are different. If I wanted to do a scientific study then yep, you are correct and a lab would be the best place. I am just doing a home comparison as that is where I will be using the cables. I also do not go to a lab to demo my AV amp purchase or a speaker purchase. Simple reason for that is the equipment will not be used in a lab. Demo rooms are designed a specific way for a reason.

Firestar_3x said:

I've got quite a few HDMI leads, first one i ever got was a 2mtr monster cable cost about £70 3 years ago, the picture quality is no different from a £3 jobbo from eBay, the only variance is build quality.

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Yes I am not surprised at all. I have never bought an expensive short HDMI cable. I have only once bought an expensive HDMI cable and that is because it is 16 meters long and showed differences with the cheaper cable. The more expensive cable was around 50% more expensive. It is hard to grade by price as I am not in the UK and things like this are much more expensive over here. The cheap cable would seem scary expensive to you guys but is the price we have to pay like the price comparison between some things in the UK and the US.

I am only looking at differences in cables over 10 meters long int he home with entry level equipment.

RB

RimBlock said:

Yeah, you see, I don't live in a lab so lab results don't have much bearing in my real world life where the variables are different. If I wanted to do a scientific study then yep, you are correct and a lab would be the best place. I am just doing a home comparison as that is where I will be using the cables. I also do not go to a lab to demo my AV amp purchase or a speaker purchase. Simple reason for that is the equipment will not be used in a lab. Demo rooms are designed a specific way for a reason.

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First off that’s a poor analogy and secondly results could be bias, it's impossible for the human eye to make a consistent judgement of improvements.

Whilst i understand as the HDMI cable gets longer you are more likely to encounter problems, i simply can't see how you can possibly demonstrate or show any difference to us using your method.

Edit: I'm not saying you shouldn't do it, i'm just saying the findings should be taken with a large pinch of salt.

The science and technicalities of HDMI indicate beyond a shadow of a doubt that it is impossible for colour precision and sharpness to be affected by cable construction (assuming like for like source comparisons), if the OP wants to try and fool himself that his purchase was justified, then I think he should go it alone..

Any test that ensures the same colour depth (i.e. deep colour as an example) and resolution is being transmitted from the source component cannot under any circumstances lead to a degradation in colour or sharpness, it just isn't scientifically possible.

The only side effect you will see is individual pixel corruption (sparklies) to one degree or another, or no picture, and that is more about noise rejection properties of the cable, something even a lot of cheap cables do very well.
Further more, if you want anything over 5M, and certainly over 10M, you would simply buy a cheapish CAT5/6 HDMI extenders and use cheap HDMI cables either end..

The only way you are going to see a difference (assuming no sparklies/picture drop out) is if
1. The resolution is changed when swapping cables
2. The colour depth is changed when swapping cables
3. You deserve to be on rogue traders and you switch to an analogue cable whilst mis-representing it as a 'cheap HDMI cable'..

Of course, you could just accept valid tests such as the DF one that everyone points to, and just admit to yourself that either the shop conned you, or you just where expecting to see a difference so convinced yourself of it..
Some of us have used many HDMI cables, over long lengths, over CAT5/6 and all used modestly priced cables, and have seen that we are getting pixel perfect resolution and colour depth with no pixel corruption at all..

In all honesty if you're testing the cable you basically need to check the signal going in one end if the same coming out the other end, no need for complicated setups or anything, you simply want to eletrically check the signal going in is the the one that comes out the end.

After all, it's a bit of wire. Anything else and you're also testing the HDMI interfaces at either end of the connection as well all the equipment required to show an image on screen or send sound to your receiver.

Taking a photo of the screen proves nothing. I'm pretty sure if you take the same photo 5 seconds later and compare it to the previous one it will show colour differences in the image.

Instead of becoming obsessed with trying to prove a difference why don't you save the time and watch a film.

Firestar_3x said:

First off that’s a poor analogy and secondly results could be bias, it's impossible for the human eye to make a consistent judgement of improvements.

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Whilst I see where you are coming from I would find it hard to advise someone to buy a projector or tv without demoing them to get a feel for how good they are compared to other models.

Firestar_3x said:

Whilst i understand as the HDMI cable gets longer you are more likely to encounter problems, i simply can't see how you can possibly demonstrate or show any difference to us using your method.

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If I could see the difference with my old eyes then I would expect to be able to pickup at lease some differences with a decent camera. I have said time and time again that it is not a definitive scientific study but may give some insight and certainly more than I have found so far from trawling the internet concerning long HDMI cables.

Firestar_3x said:

Edit: I'm not saying you shouldn't do it, i'm just saying the findings should be taken with a large pinch of salt.

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I would not suggest otherwise. This is just me testing with a home setup in the most controlled conditions I can arrange with the equipment I have. But... to this end it is going to be closer to standard usage than testing in a lab.

You could always suggest improvements that may be possible within the bounds I have already set. That may be quite helpful.

RB

Demon said:

The science and technicalities of HDMI indicate beyond a shadow of a doubt that it is impossible for colour precision and sharpness to be affected by cable construction (assuming like for like source comparisons), if the OP wants to try and fool himself that his purchase was justified, then I think he should go it alone..

Click to expand...

Thanks for your input.

Demon said:

Any test that ensures the same colour depth (i.e. deep colour as an example) and resolution is being transmitted from the source component cannot under any circumstances lead to a degradation in colour or sharpness, it just isn't scientifically possible.

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And yet proposing to see if there are any differences has you pointing fingers about rouge traders. You seem to very much dislike the idea of me even looking at this. If all cables are the same then why would the change cause a resolution change or a colour depth change ??. What you seem to be saying is that if there is any evidence however subjective of any picture quality change for whatever reason then I am lying and changing to analogue cables. If that is what you believe then there is little I can do to stop you. If you are right, and I have no reason to believe you are not, then all it will do is prove what you say so it seems strange to have such a strong reaction to a suggest of a basic test. I guess some people are very passionate about these things.

Demon said:

...Further more, if you want anything over 5M, and certainly over 10M, you would simply buy a cheapish CAT5/6 HDMI extenders and use cheap HDMI cables either end..

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Why ? when it would cost me around 150 for that lot and my expensive cable was 180. One cable, no converters less hassle for an extra 30 quid.

Demon said:

Of course, you could just accept valid tests such as the DF one that everyone points to, and just admit to yourself that either the shop conned you, or you just where expecting to see a difference so convinced yourself of it..

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Who ever said I don't. [sigh]... have you never wanted to do something for yourself rather than relying on other people tests in lab conditions.

Demon said:

Some of us have used many HDMI cables, over long lengths, over CAT5/6 and all used modestly priced cables, and have seen that we are getting pixel perfect resolution and colour depth with no pixel corruption at all..

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And you gained that experience by trying for yourself. Yet you are so strongly protesting that I shouldn't bother or is it just the suggestion of providing the results of me trying that upsets you ?. Why can others not be allowed to do what you have done or are you just trying to protect the poor innocent forumers ?

Oh well, never mind.

RB

Following on from Demon's post, HDMI includes for two-way comms including a DDC handshake covering the supported resolutions of the display device.

This is speculation, but if there were some sort of negotiation of bitrate (e.g. similar to autonegotiation over ethernet) then it could mean that cables with different attenuation or noise characteristics could result in different maximum resolutions or colour depths (etc.).

Anyone confirm one way or the other?

RB, whilst the camera is indeed a good one, the camera may meter off a different part of the screen and adjust accordingly, so you couldnt guarantee that the same cables picture will be the same more than once - its just how photography is i'm afraid, and a long exposure wouldnt help with that.

imo, if i were you, i'd do the test, and use your subjective opinion. The results will only be valid for you, but will be more accurate for you. To do that subjectively, imo, you'll need someone changing the cables and you just witnessing the picture. I dont even think youcould grade out of 10 - i think you need a list of things to check, and go with a general "feeling" without knowing the brand of cable being used...

That said, i thought everyone knew HDMI quality mattered over length. As for using CAT5/6, well i think we're wandering into the realm of specialist here, and this isnt something the average joe who drops cash on these things is going to investigate.

Do the comparison, but do it for yourself i guess is my point.