6 replies to this topic

[Campos]

Hi all,

 

I'm scratching my head here lattely thinking about an issue with the use of accessories like coma correctors, reducers, etc using different types of camera modifications (full spectrum mod, LPF2 only removal, Baader ACF filter mod...)

 

The thing is that with the use of such acccessories one must keep the distance of about 55mm for them to work properlly, but at least in my head, the removal of all filters like in a full spectrum modification changes this distance VS say a Baader modification (all filters in place) at least optically but not mechanically, is this correct or I'm a seeing it wrong?

 

Let me know your oppinions please?

 

Many thanks, 

 

Luís

Edited by Campos, 23 January 2015 - 09:06 AM.

[Gary Honis]

Hi Luís,

 

If you did a full spectrum modification by removing both original filters and not replacing with a clear glass, the sensor would need to be moved 0.46mm toward the lens or reducer.  There is not enough space inside most cameras to do that.

 

Maybe a half of a mm is not enough to worry about the 55mm spacing requirement.  I would think there must be some tolerance allowed around 55mm.

[Campos]

Hello Gary

 

Many thanks for your input on this, I ask because on the monomods I do I remove all filters, including cover glass and then replace with an Astronomik MC clear glass due to it's excellent A.R. coatings, so it's basically the same as a full spectrum mod in terms of "filter" thickness, on cameras with shims (450D for ex.) I remove the "thicker" ones and lower the sensor assembly, with collimating screws I lower about 0.5mm each so I guess it's ok

 

My only concern is that if this is not made the measure tolerances with one of these accessories might became affected, so we are doing it right

 

Thanks again Gary

[Gary Honis]

Hello Gary

... on cameras with shims (450D for ex.) I remove the "thicker" ones and lower the sensor assembly, with collimating screws I lower about 0.5mm each so I guess it's ok

 

 

Hi Luis,

 

If you are lowering the sensor by 0.5mm, you are lowering it too much when using the Astronomik MC Clear Glass replacement.  The sensor needs only to be moved 0.15mm towards the lens.

[Campos]

But that's because I also remove the sensor coverglass, so that extra missing element needs also be taken into account, so basically in the end I'm removing the LPF1 and LPF2 and also sensor coverglass, then I replace this sensor coverglass with the Astronomik MC clear glass, but only in monochrome conversions, hence the need to replace the coverglass as this one strangelly has no AR coatings at all and causes bad reflections with a debayered sensor.

 

Cheers,

[Gary Honis]

Hi Luis,

 

Thanks for the explanation.  Is it the original coverglass that has no AR coatings?  Are you able to ever reuse the original coverglass?

[Campos]

Hi Gary,

 

Yes it's possible to reuse it, but I allways exchange that for the astronomik, I have a bag full of coverglasses now...hehehehehe  Canon isn't using AR coatings on their coverglasses because on a original sensor the microlenses are not reflective and but a debayered sensor gets really shinny and light bounces from sensor surface to coverglass, Astronomik replacement is the way to go with this

 

BTW, I've measured yesterday those thicker shims and they are not 0.5mm as I told you sorry about that, they are in fact 0.35mm, so that's what I'm lowering in reallity.

 

So bottom line, whit the reducers there must be some tolerance around the spec'd 55mm distance, maybe 1mm off or so is not something to worry about

 

Thank you Gary!

 

Cheers,