another fool with a half plate camera

[Ole Tjugen]

The speed of the Anastigmats of the period was their prime selling point.

No, the selling point was their greatly reduced astigmatism which gave a flatter image field - or at least an evenly curved one which didn't depend on orientation of the subject.

Really fast Aplanats were down to f:4 (but very few, Petzvals were preferred for this); "normal" ones were f:7 to f:8, wide field from f:10, and wide anle around f:16. Note that the Protar (serie V) was f:18...

[Andrew M]

Hi Ole,

now that the words Clement et Gilmer has been suggested it is easy to make out the lettering as such, with the exception the 'et' still looks like a little artistic flair has been used and is difficult to make out as that easily, the word Clement is now obvious except it does have a little ' over the first "e" in the word.

the visable diameter of the front lens appears to be 33mm (33x8=264), which would make it a longer focal length at 264mm.

i dont think it looks like a triplet, the front and rear lens measure the same diameter and appear to be the same thickness (i unscrewed them to measure) and no third element. i am not sure how to tell if the lens elements are cemented but the shapes of each lens appear consistant with the diagrams in Kingslake's lens book dipicting the Rapid Rectilinear, Aplanat and Euryscope (all the same design with different names according to this book).

[Glenn Thoreson]

Ole, you're right and not entirely right about the early Anastigmats. Most literature I have from the period doesn't usually mention the astigmatism part. It really pushes the speed. I think this was meant for the amateur who wanted to be able to take pictures in poor light and be able to go home the same day. In fact, that was exactly the pitch that was put forth in the advertisements. Other literature I have buried in this mess lists the f/6 lenses as Extra Rapid Aplanats. I don't suppose, by any means, that they all were, though. My Busch Detectiv Aplanat f/6 is engraved Extra Rapid, also. I suppose that means it's more rapider that the f/8 variety, or f/4 US, if you will. It's a great mystery, I tells ya! I live by the advice I usually give others though - "What difference does it make? Shoot some film and see if it makes a picture". Most of 'em do.

[Andrew M]

Your focal length measurement method is basically entirely correct and limited only by the accuracy of setting infinity and 1:1 focus.

thanks for the confirmation Ernst. i'm confident i was accurate with measuring, more so the extra times i did it. i used a paper thin ruler on the glass and matched it to the ruler on the wall using a lupe. it certainly took some time and not as quick/easy as i thought it would be (not difficult tho). it was neccesary to move the camera back or forward very small amounts to get it perfect and of course fine focus adjustments. also level with the ruler on the wall.

i'm not sure how accurate the 8x the front diameter method is..i just checked against some other lenses with the focal length written on them and it doesnt match up the same