Achtung: The MARK S 710 D is now fitted with...

[Stuart Budd]

That's embarrassing. I thought those grooves were independent of one another but they are infact a thread. Did the thumb nail in the groove test whilst rotating.

Here's a Eumig 720 lens. The groves are zoom stops as Maurice mentions. Zoom steps. And as stated, rotate to focus.

Thanks for aging it for me Erik. Think it may have been on a damp box since 73.
Production and retail does intrest me. Going back to early American clocks, often the case stock was produced for some years to come. Seth Thomas clocks would have Thomaston cases with Plymouth Hollow clockworks as stock of brass clockworks were produced by the 100s if not 1000s. After Seth's death the town being renamed to Thomaston from Plymouth Hollow. I can see stock of 700/800 cases being made by the quantity and during the cross over parts being used up to suit.
May be, may be not

[Stuart Budd]

So, both my 710 D's don't have focus knobs.
Unit 3709064 has no facility to accept focus knob and small focus spring thread.

My other bought earlier unit 3725500, a later version, again no focus knob. Does have facility to accept one. Currently has spring thread, larger than previous model.

Even cover has option built in. Part no. 718 4001/1 early no hole. 718 4002/3 hole. Hole covered by model name plate.

Early 3709064 (my new one in need of TLC or CLA)

And 3725500

Don't know how many other changes but noticed the lamp case is different too.

[Stuart Budd]

Better add the lens types. Screw thread, left Bolex 1.3 15-30mm 15mm giving the biggest screen size. Right Eumig, same fitting and lens spec. Middle, Eumig focus knob style with flat focus portion. 1.6 17-30mm.
I'll make the assumption that a small f stop 1.3 will have a shallow focus compared to 1.6. So 1.6 possibly easy to focus but less bright.
Also unsure if the f stop is constant across the zoom. So maybe 1.3 at 15mm is say 2 at 30mm. Really don't know.

Anyway

[Joseph Banfield]

Well Stuart, that is a good assumption that the faster the lens, the more critical the focus becomes. In my experience a film that is warped is going to look great with a f 1,6 but look nasty with a f 1,1. And yes, when using a f 1,6 you are not going to be getting as much light when using a f 1,1 or even a f 1,0.

What I have found works the best across the board with every film type is the early screw type Eumig f 1,4 zoom lens. There is something about that particular lens that looks great on screen. Yea, you loose a bit of light but the image is fantastic from edge to edge and the contrast is superb with the light looking noticeably more white. In my opinion it is better than the more standard f 1,3 lens, that to my eyes looks a bit less contrasty and leans to the yellow spectrum of light, and I have five of those lenses with equal results.

[Brian Fretwell]

I've always thought the 18mm f1.6 Eupronet fitted to my Mk 501D was one of the best, though I haven't used it recently. I'm pretty sure I bought that version after reading a Movie Maker review that said it was better than the zoom version. It would have the advantage of less elements and is a screw fitting (not focus knob) lens.

[Shane C. Collins]

Not Eumig, but, my Bolex 1.3 "hifi" 15mm prime lens is superb! I have this fitted to a Honeywell Elmo FP8-C projector. Makes all my films come alive. It's the best lens I've ever used. Blows all zoom lens away in my opinion. The 15mm makes it nice for short throws to fill the screen.

[Stuart Budd]

Thanks for the feedback on lenses from the more experienced amoung us. The kit zoom is like the 35mm camera zoom, a good start. Once you understand your viewing room and size to distance and light output, a prime of suitable angle is the ideal. But that too is down to quality of film flatness.

[Lee Mannering]

All correct Stu.
I'm probably not the only one who converted a Eumig 824 Sonomatic to threaded focus making a small bracket with brass slot to guide the threaded lens.
My HID lit 824 has this focus modification and my fave lens in it a Schneider f1.1 a noted quality lens with film makers back in el day usually found in Norisound machines en mass. Keep en eye out for one of those lenses a thing of beauty.