35 mm equivalence.

[Warman]

Was just wondering. The G3/5 has a 35 mm equivalent of 35-140mm which is suposed to be 4x. With a 1,75 teleconverter do i get 61-245mm meaning a 7x zoom? I ask this because for instants the Pro1 also as 7x zoom but its equivalence to 35mm is 28-200 mm. Is that because of the wide capacity of the lens?

[darrylr]

No you don't get the full range at 1.75x. You have to be fully zoomed or back a little bit from full zoom. If you go more than this you get vignetting. I would say something like the 110-140mm range you can get 1.75x so something like 190-245mm with the Canon TC-DC58N. I have heard that will other tele extenders you can only use them at full zoom in order to not get vignetting.

On the Pro1, the built-in lense is made to be able to use that full range. There is an SLR lense called the nicknamed the Bigma from Sigma which is 50-500mm all with the one lense. It is all in how the lense is made.

-Darryl

[Andy_T]

Was just wondering. The G3/5 has a 35 mm equivalent of 35-140mm which is suposed to be 4x. With a 1,75 teleconverter do i get 61-245mm meaning a 7x zoom? I ask this because for instants the Pro1 also as 7x zoom but its equivalence to 35mm is 28-200 mm. Is that because of the wide capacity of the lens?

4x zoom means that 140 divided by 35 gives a factor of 4.
200 divided by 28 roughly gives 7, there's a larger proportional difference between the 'close' and the 'wide' setting.

245 divided by 61 still gives 4 ... unless you are really fast in screwing and unscrewing your lens to the adapter and do it in mid-zooming :lol:

Best regards,
Andy

[Warman]

I finaly got my TCON17 and was just wondering how much zoom i have now in 35 mm terms. :)
The lens quality is great but the lens is also huge and heavy.What i didnt expect was to have a range where the adaptor is seen. I didnt notice any vigneting at any zoom.

[darrylr]

I think what you call "a range where the adapter is seen" is what I called vignetting. You can see the black circle around the outside of the frame if you are not close to full tele zoom. That is normal with these tele convertors. Unless of course you mean that the viewfinder (not LCD) is blocked due to the size of the tele convertor.

-Darryl

[Warman]

To me vigneting is the distortion of the edges of the picture due to lens effect. In my case, the adaptor is clearly visible in the LCD more or less up to half the focal distance available.

[dbump]

I don't want to get pedantic here :) but I probably will. When I started looking at teleconverters, I had no clue what vignetting was--googling for the term didn't produce any definitions pertinent to lenses. Since then, I've deduced from context (mostly example images) that vignetting is darkened or simply black corners. In extreme examples, as with astrophotography, the image appears as a black rectangle with a picture-colored 'hole' punched in the center of it.
Check http://www.ugcs.caltech.edu/~pinkston/astronomy/canon-g2/ for some good examples, especially at the bottom of the page.

I believe what you're describing is simply distortion, or even achromatic distortion, in which you get color fringes on objects in the corners--usually on cheaper converters.

None of which helps the problem you're running into. Black corners aren't good, regarless of what we call them. That's one thing (cost is another) that has kept me from getting a teleconverter, even though I'd love to have more zoom.

Aside from the relatively fixed zoom and weight of the lens, are you pretty happy with the TCON?

[Warman]

I always associated one with the other but i guess, based on your input, that what i was talking about was barrel distortion? Anyway, i realy wasnt expecting the vigneting but it doesnt bother me. The quality shots coming from the TCON-17 is great and i'm happy with the tele.
btw, its settled then that it is 245mm?

[gcogger]

Vignetting is not usually as abrupt as dbump describes - it's more often a slight darkening of the corners of the frame. There are some examples at:

http://www.photozone.de/3Technology/lenstec3.htm
http://www.vanwalree.com/optics/vignetting.html

[dbump]

Excellent links, gcogger! The first one is a great overview of a range of lens issues.
Thanks!