Opticallimits

Sillier it gets.

 

The Eg focus screens have the same thickness, thee is no variation in production. There are no shims involved when exchanging one for another, at all. The camera housing and focus screens are manufactured to such tolerances that once does not have to bother with shims when exchanging one Eg screen for another.

 

Like I wrote before, only when one gets a 3rd party screen fiddling with shims may be needed.

 

Do I have experience with exchanging the standard Eg-A II focus screen with Eg-S Super Precision focus screen? Yes I do. Do I have experience with manual focussing with this screen together with shallow DOF  of f2.8, f2, f1.8, f1.2 lenses and their shallow DOF? Yes I do. 

 

Can one get accurate results, manually focussing with Eg-S and large apertures? Yes one can. Is it fast and easy? Yes, indeed.

 

Do trolls want to troll? Apparently.

 

When I manually focus through the viewfinder with the Eg-S screen on the B, the resulting image is focussed on the B, even near MFD (0.6m).

Canon FL 55mm f1.2 (1967 lens).

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I don't think I ever said changing the focus screen would make you need to shim it, all your factory screens may or may not need to be shimmed with one particular lens or more but you  may not realize it because you're lucky or relying on some other MF assist than visual confirmation on the focusing screen.

 

Also a personal recommendation, stop calling people names.

It is total nonsense to state that shimming is reliant on a particular lens. Think that is just ignorance in the matter.

If you have 9 lenses that focus fine and one lens that needs microadjustment, you'd pretty much have to either shim for that particular lens or get another copy, if you wanted to do manual focusing inside the viewfinder. 

 

Also, adding this form of negativity to the end of every message is generally considered to be being a useless asshole who thinks they can make their argument stronger by insulting the other party. You may not think that but everybody sees it that way so it would be really beneficial to your quality of life if you stop doing that.

Well, in any camera with exchangeable lenses the view finder is shimmed one way or another. With fixed focusing screens it generally is the focusing screen, with exchangeable focusing screens it normally is the frame into which the focusing screens are inserted.

 

What also is shimmed is the lens mount, to make sure it is exactly at the right distance and parallel to the sensor. Besides this, obviously mirror assembky and sub-assembly for AF etc. are adjusted as well.

 

Lenses are shimmed as well, as in, the lens mounts are.

 

Even with all this adjustment, it still is almost impossible to get it 100% right, but mostly it falls within tolerances, after all the shimming done, apart from focusing by means of AF - as lenses need to move relatively loosely, it sometimes requires individual adjustment per camerabody.

 

In short, all focusing screens are shimmed, whether that is doen directly or indirectly, or at least are shimmable, as indeed occasionally no shims are needed.


Do also note that shims are not necessarily equally thick on all sides. They come in a lost of varieties tfor exact positioning on all sides.

 

Kind regards, Wim

Quote:If you have 9 lenses that focus fine and one lens that needs microadjustment, you'd pretty much have to either shim for that particular lens or get another copy, if you wanted to do manual focusing inside the viewfinder. 

 

Also, adding this form of negativity to the end of every message is generally considered to be being a useless asshole who thinks they can make their argument stronger by insulting the other party. You may not think that but everybody sees it that way so it would be really beneficial to your quality of life if you stop doing that.

That is nonsense. A lens that needs microadjustment either does a wrong final step with PD AUTO FOCUS or has one colour which focusses on a different plane which the AF sensor picks up on.

 

Neither has anything at all to do with the focus screen, or the imaging sensor. 

Wait, why do you think some lenses take that wrong final step with PD AF?

Quote:Wait, why do you think some lenses take that wrong final step with PD AF?

I do not think it, I know it. The difference between merely opinion and fact.

 

AF is totally separate from the focus screen, so not going to discuss PD AF algorithms. 

 

Better question: Why do you think the focus screen is linked to the AF system, and why do you think the focus screen should be a different distance for different lenses, while you do not think that about the imaging sensor?

Stop showing off your superior knowledge and tell me why some lenses take that wrong final step with PD AF?

Quote:Stop showing off your superior knowledge and tell me why some lenses take that wrong final step with PD AF?

No, there is no use in that. We are discussing focus screens and the ability to judge focus with our eyes.. Besides, i do not know WHY some lenses take wrong final steps as I am not the designer of that lens, have not designed its electronics, logic, gears, sensors and algorithms. I just know that when it happens one needs to send in the lens for fixing/calibration, Or some lenses just do it without calibration being an option to help it, just crude AF implementation (some Tokinas come to mind).

 

Are you at least now clear on that the focus screen has no relation to back or front focussing but that front and back focussing occurs with AF, a result of the AF system (be it wrong size steps being taken or the AF sensor looking at a certain colour which does not focus at the same plane as the other colours) or MF relying on focus confirmation of the AF sensor with the latter collour focus issue?