Goody
Established
Does anyone know if the Canon 100mm f/3.5 (older model - black and silver) which takes a 34mm filter takes a fine (.50) or a medium (.75) pitch filter. I picked up an adapter for series 6 from Filterfind and it will not screw in much. They think it might be the wrong pitch.
Mackinaw
Think Different
How do you determine thread pitch? I have a black & chrome Canon 100/3.5 and an authentic Canon 34mm screw-in filter. I'll measure it, if you tell me how.
Jim B.
Jim B.
Robert Lai
Well-known
You need really, really good vision, or a loupe.
Hold up a millimeter ruler perpendicular to the filter.
If you see two full threads between the millimeter marks, then you have a 0.5mm pitch. If less than 2 threads, then 0.75mm pitch.
I suspect that these older lenses used the 0.5mm pitch. The modern ones tend to use the 0.75mm pitch.
For my 1930s 90mm Elmar f/4, which has a 34mm filter size, a B+W filter has the correct pitch. Most of the other filter companies make the modern pitch, which doesn't fit.
Hold up a millimeter ruler perpendicular to the filter.
If you see two full threads between the millimeter marks, then you have a 0.5mm pitch. If less than 2 threads, then 0.75mm pitch.
I suspect that these older lenses used the 0.5mm pitch. The modern ones tend to use the 0.75mm pitch.
For my 1930s 90mm Elmar f/4, which has a 34mm filter size, a B+W filter has the correct pitch. Most of the other filter companies make the modern pitch, which doesn't fit.
Spavinaw
Well-known
As far as I know the pitch is 0.5mm. The fact that your adapter does not screw in very far is a very good sign that it is 0.75mm pitch.
Mackinaw
Think Different
Very hard to measure. The Canon 34mm filter I have is of the "thin" variety with a bare minimum of threads. Following Robert's measuring advice, It looks to be a 0.75mm pitch.
Jim B.
Jim B.
Livesteamer
Well-known
The proper way to measure thread pitch is with a thread gauge. It looks a lot like a feeler gauge but each blade has teeth of a different pitch. 1mm, .75mm, .5mm and so on. When you hold the gauge up against the threads to be measured it becomes easily apparent which gauge fits and which don't. Joe
davhill
Canon P
Sure, like we all have one of those. The practical way
to measure thread pitch is to compare your filter threads to a common modern filter, like a Vivitar or whatever. Use magnifiers and bright light, because everything is very small and very black. If the threads match, you’ve got 0.75mm pitch. If the Vivitar thread is fatter, you’ve got 0.5mm pitch. If you can see them, the difference is noticeable, even glaring. Those are the only options. The other way is also simple: if what you bought only screws part way in, you have the wrong one. Buy the other one. There’s only two choices.
Spavinaw
Well-known
Enough already. In my previous post I stated that as far as I knew the pitch was 0.5mm and that if an item did not screw in very far it was 0.75mm pitch. Well since the discussion continues, I got up off my lazy bottom, walked to the other end of the house, got out my Canon 100mm lens, got out the Series 6 adapter ring that fits it, and screwed the ring into the lens as a test. All the threads screwed in completely. The filter adapter ring is engraved "34 F 6". The cardboard card the filter ring originally came on (yes,till have it) is stamped "34F-6". Bottom line: The Canon 100mm f3.5 black and chrome LTM lens has fine pitch (0.5mm) threads. Period.
Livesteamer
Well-known
I did not mean to cause dissent. I'm a retired machinist and I don't even have a metric thread pitch gauge altho I have access to one where I work. Earlier posts suggesting a magnifier and a good rule are a practical method. I do have a large Starrett thread gauge in inch measure and that could get me close enough to interpolate. Joe
Goody
Established
Thanks -- really appreciate this !!!