Cartridge alignment — the parallax effect

the thin end of the wedge
Japi Roelofs
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Cartridge alignment — the parallax effect

Post by Japi Roelofs » 23 Jan 2020 15:44

OK first off apologies for the blurry pictures, my phone doesn't do close-ups very well.

So here's two pictures of a cartridge I'm aligning. Well actually I'm aligning the cantilever, not the cartridge body.

Which one of these two pictures looks correct to you?
Alignment A.jpg
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Alignment B.jpg
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Well I'll give you the answer myself: they are both completely off.
In the first picture, the cartridge is twisted to the left. In the second picture, the cartridge is twisted to the right. The grid is the same in both pictures.
Cartridge A.jpg
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Cartridge B.jpg
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The reason why the cantilever appears to line up with the centre grid line in both pictures is called the parallax effect. I moved the camera a little bit to the left, and to the right, to make it look in line. If you look at the white stylus assembly in both pictures, you'll see that the right side is more exposed in the first picture, and vice versa in the second picture.

But we're looking at the cantilever, not the cartridge body. After all, the cantilever may not be sitting perfectly parallel to the body.
So what is the reference point here? Ideally it would be a point on the 'horizon', perfectly centered, where the lines of the grid come together. But of course in the real world there's no such thing....

How do you guys deal with this problem? A mirrored protractor would seem to be the answer, but my printer kind of doesn't do mirrors.... I have been experimenting with printing on transparent film sheets, and putting a mirror underneath. But the mirror is small and doesn't support the protractor properly. I guess I need a bigger mirror.

Any thoughts?

patient_ot
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Re: Cartridge alignment — the parallax effect

Post by patient_ot » 23 Jan 2020 16:09

If the cantilever is not perfectly centered, then the cartridge is basically defective and should go back. That or it was twisted by applying too much or too little anti-skate, your tonearm is out of whack, etc. I make sure the cart body is centered by using the edge of a razor blade with the headshell. I then use an arc protractor or a jig to make sure it is aligned properly. Since I use Stevenson alignment, no twisting of the cart body is required. Carts made with poor tolerances or if you are using Baerwald alignment may require turning the cart inward toward the spindle. Pictures like the ones you posted don't tell me anything. I always check the cart from multiple angles on the protractor or jig.

Japi Roelofs
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Re: Cartridge alignment — the parallax effect

Post by Japi Roelofs » 23 Jan 2020 20:45

I do agree that using the manufacturer's alignment method makes things a lot easier: set the correct overhang and make sure the cartridge sits straight in the headshell — done.
IMO aligning a cartridge to a headshell is easier than aligning it to a grid: there's less room for error, especially if you have a headshell with a printed pattern on the bottom, like this one from Nagaoka:
Nagaoka headshell MG-704.jpg
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But there's lots of situations where one has to revert to aligning to a grid, be it on a two-point or on an arc protractor.

- headshell doesn't have straight sides
- cartridge doesn't have straight sides
- different alignment method from manufacturer
- manufacturer doesn't provide tonearm information
- cantilever orientation less than perfect but not bad enough to justify a return
- sliding base tonearms (SME)

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Re: Cartridge alignment — the parallax effect

Post by bra10n » 23 Jan 2020 21:16

patient_ot wrote:
23 Jan 2020 16:09
...If the cantilever is not perfectly centered, then the cartridge is basically defective and should go back...
I agree.
Personally if I bought a new cart/stylus combo or stylus that didn't have a centered cantilever then I would return it.

Conversely, if it was me who knackered the stylus then I'd hope to understand what causes this unfortunate situation. Japi, you elude to some of these possible factors;
Japi Roelofs wrote:
23 Jan 2020 20:45

But there's lots of situations where one has to revert to aligning to a grid, be it on a two-point or on an arc protractor.

- headshell doesn't have straight sides
- cartridge doesn't have straight sides
- different alignment method from manufacturer
- manufacturer doesn't provide tonearm information
- cantilever orientation less than perfect but not bad enough to justify a return
I understand this predicament if buying used or a cart or a stylus comes as part of the deal. What I'll never understand though is the dismissing attitude of some here of others who support manufacturers providing specs, geometry info and technical support (which the cost of is included in the cart, arm or stylus... to the dismay of some). These individuals appear to focus on $ spent rather than value :roll:

You get nothing for nothing in this hobby. We all know it, but choose to ignore it or otherwise disregard it. Human nature... no rhyme or reason.

Japi Roelofs
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Re: Cartridge alignment — the parallax effect

Post by Japi Roelofs » 23 Jan 2020 21:54

To be clear: my original post wasn't because of a knackered cantilever, or some other defect.
Basically there's two reasons why I made the post:

1) you see a lot of pictures appearing here on the forum, from people asking if they did a good job aligning their cartridge. Looking at those pictures I often think that it's impossible to judge, because of the way the picture was taken, or more specific the angle of the camera.

2) a lot of people here on the forum insist you should align the cantilever, not the cartridge body.

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Re: Cartridge alignment — the parallax effect

Post by bra10n » 23 Jan 2020 22:28

I realise Japi, but my point is why do some look down on others who just might be learned and savvy enough to avoid some of these basic pitfalls. It's just like liars who generally get to claim their version of events first, and always the truth bringing up the rear. If minimal spend $ is the only objective then on what basis is there a need for any manufacturer to go over and above in terms of QC, specs, support, design etc.

*If* you buy a pig, expect it to oink. Of course, used and vintage is an entirely different kettle of fish.

Apologies if I've derailed your thread. I've made my point thus...

Back O/T...
Japi Roelofs wrote:
23 Jan 2020 21:54
...2) a lot of people here on the forum insist you should align the cantilever, not the cartridge body.
You either accept the requirement for a cantilever to be square in the clamp or you don't. If you don't, fine I'm ok with that. True a skewed cantilever still plays, so what's the problem? That I'm afraid is a question each of us must answer for ourselves :lol:

My *mood* stems from those who choose to ignore advice or who err of themselves, and then it's a shoot down of manufacturers/products because things didn't work out as they had hoped.

cheers,

D

Japi Roelofs
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Re: Cartridge alignment — the parallax effect

Post by Japi Roelofs » 23 Jan 2020 22:37

Sorry Bra1on, you lost me.... all I was trying to do was to explain the parallax effect, and the problems it can cause.

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Re: Cartridge alignment — the parallax effect

Post by bra10n » 23 Jan 2020 23:50

Sorry then Japi.

I suppose I am on about how and why many on here seem to find themselves in various predicaments (eg dealing with parallax effects) trying to align a damaged stylus via the cantilever...

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Re: Cartridge alignment — the parallax effect

Post by noisefreq » 24 Jan 2020 00:17

You can tell by the sides of the cartridge body that the camera is not centered on the cartridge.

I find myself closing one eye as I line up the protractor and making sure I'm looking straight on to the cart to line up the cantilever.
Kind of like looking through a rifle scope.

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Re: Cartridge alignment — the parallax effect

Post by sliceofhogan » 24 Jan 2020 09:11

Just use your mothers make-up mirror. Steal it from her handbag, put it under your cartridge.
Then align using the reflection.

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Re: Cartridge alignment — the parallax effect

Post by scho2684 » 24 Jan 2020 13:13

Excellent observation and topic...
You have managed to get that effect perfectly photographed!
And this effect applies not only with aligning the cartridge on grid, this also plays a role in VTA or even more dangerous: SRA

What you could do is attach a clear foil from any kind of packaging on top of the grid which gives you some mirror effect...

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Re: Cartridge alignment — the parallax effect

Post by scho2684 » 24 Jan 2020 15:14

Japi Roelofs wrote:
23 Jan 2020 15:44
Any thoughts?
Japi. I think, in case of a camera usage, that you need to make sure that the camera is looking exactly parallel to that grid.
In the two pictures you have taken you can see the lines are not horizontal/vertical, they appear to be looked at from a angled view...

If you have that grid correct in the camera view, then that parallax effect plays no role.
So line up camera first, then after that only move the cartridge...

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Re: Cartridge alignment — the parallax effect

Post by backtotheblack » 24 Jan 2020 17:05

noisefreq wrote:
24 Jan 2020 00:17
You can tell by the sides of the cartridge body that the camera is not centered on the cartridge.

I find myself closing one eye as I line up the protractor and making sure I'm looking straight on to the cart to line up the cantilever.
Kind of like looking through a rifle scope.
yes but you must use your dominant eye https://www.allaboutvision.com/resource ... e-test.htm the best way is to punch a hole in a sheet of paper with a pencil as your "scope".

i learnt this when i was a very young lad doing archery. i happen to be right handed but left eyed.

Japi Roelofs
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Re: Cartridge alignment — the parallax effect

Post by Japi Roelofs » 24 Jan 2020 21:29

scho2684 wrote:
24 Jan 2020 15:14
Japi. I think, in case of a camera usage, that you need to make sure that the camera is looking exactly parallel to that grid.
In the two pictures you have taken you can see the lines are not horizontal/vertical, they appear to be looked at from a angled view...

If you have that grid correct in the camera view, then that parallax effect plays no role.
So line up camera first, then after that only move the cartridge...
Marco, I got your PM, not sure if you got my reply as it seems to be stuck in the Outbox. Anyway, sure can you use these pictures...

The pictures I took were just to show how the eye can be fooled. I deliberately mounted the cartridge in two completely different angles. So the results are extreme, the difference in offset angle being up to tens of degrees. Normally, the effect is much, much more subtle.

I totally understand that the camera, or the eye in most cases, needs to be in the correct spot, looking straight at the grid. But that was my whole point: how do you know exactly what the correct spot is? The mirrored protractor still seems like the most fool proof method.

Re. aligning the cantilever, and not the cartridge body: here's a quote from Ortofon, from their website.

"When aligning a cartridge for tangency using the alignment protractor, it is essential to remember that you are attempting to align the cantilever (and, hence, the stylus), not the cartridge body. There is no guarantee that the cantilever is perfectly aligned within the cartridge body, so simply aligning the cartridge body will not necessarily produce the desired result."


https://www.ortofon.com/protractor-p-452

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Re: Cartridge alignment — the parallax effect

Post by jdjohn » 24 Jan 2020 22:15

noisefreq wrote:
24 Jan 2020 00:17
I find myself closing one eye as I line up the protractor and making sure I'm looking straight on to the cart to line up the cantilever.
Kind of like looking through a rifle scope.
Also, placing a strong light source behind the cartridge (like a pen flashlight), will give you a silhouette of the cantilever. With that look, it should appear as a straight line from where the cantilever exits the stylus assembly, down through the tip, and extend onto the front grid line coming towards the viewer. When straight, it should all appear as one continuous straight line. Maybe one day I can capture a pic of this.

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