Canon KJ20x8.2B IRSD Lens On An EX3

[Ronald Jackson]

I'm trying to find out, or get an informed opinion, as to how this lens, via say a Fujinon ACM-21 adaptor, will , at full zoom plus extender, compare with a Nikkor 80-400 AFS "stills" lens at full zoom.

Wildlife (birds) video so more often than not the lens(es) would be stopped down a stop or three.

I have the Nikkor lens and find the limited zoom range and user-hostile lens changing facility on the EX3 a real bind. More or less stuck in the field with either the stock lens, too short, or the Nikkor, too limited, with no facility for a quick change of lens.

Thus a lens such as the KJ20 might be a solution albeit at a price,

Ron

ps image quality is what I'm after comparing. Maximum focal length will be more or less similar

[Doug Jensen]

I think you better do your math again. Even though the Canon lens has a 2x extender, the "apparent" maximum focal lengths will not even be close between those two lenses.

[Ronald Jackson]

Sums actually Doug! Nikkor AFS 400mm max. KJ20 328mm max with 2x extender, x1.357 'cos 2/3 lens on a 1/2 inch camera equals 445mm.

More or less the same I think. Huge difference at the wider ends which why I'm interested, all other things being equal.


Ron

[Doug Jensen]

Sorry, I misread your post!

[Bo Skelmose]

Hi I have used a canon J20x8 and a Sigma 120-320mm (or was it 300mm) on my EX3. I must say that using the extender on the canon lens does not give very sharp pictures. BUT you can never work very fast with the Sigma lens - just to find the bird can take so long that the bird has gone before you are ready. With a Zoom lens, like the canon, you can quikly zoom out and find the bird and zoom in. Flying birds is extremely difficult to film with my Sigma lens.
I made this a couple of years ago on my EX3 and the Sigma in 720-50P.

Ringdue (Columba palumbus) on Vimeo

[Ronald Jackson]

Thanks Bo- the Sigma images certainly okay-do you have similar for the Canon? Is that Canon lens Standard Definition by the way? I understand that HD DOES make a difference. Maybe I get a longish B4 lens without a built in 2x extender and add something like a Century 2x that fits the front of the lens.

Such a pain trying to change lenses quickly without having a table in front of you. I had/have an XLH1 where lens change was as simple as on a DSLR.

Still interested in an opinion of how this particular newish lens stacks up with the extender extended.


Ron

[Ronald Jackson]

p.s. maybe your Sigma was the 100-300 F4, constant aperture which one of their best lenses I think. Unless a 120-300 F2.8 which v good but heavy needing a rod system, all adding to time needed to switch lenses.

[Alister Chapman]

Originally Posted by Ronald Jackson

Sums actually Doug! Nikkor AFS 400mm max. KJ20 328mm max with 2x extender, x1.357 'cos 2/3 lens on a 1/2 inch camera equals 445mm.

More or less the same I think. Huge difference at the wider ends which why I'm interested, all other things being equal.


Ron

NO NO NO NO! The focal length of the lens does NOT change when you put it on a different camera. The KJ20 will still be a 328mm lens, just as the Nikkor is still a 400mm lens, no matter what camera you attach it to.

The so called crop factor affects the Field of View, not the focal length, so the 328mm of the KJ20 will result in an FoV narrower by 1.35 on a 1/2" cam than than on a 2/3" camera, but the focal length is still 328mm, so compared to the Nikkor 400mm, on the a camera with the same size sensor it will not be as telephoto.

I really wish people would understand that crop factors apply to the field of view and not the focal length, they are completely different things. By applying crop factors to the focal length it creates all kinds of confusion, as here where Ron has magically made the KJ20 appear to have a longer focal length than the Nikkor 400mm by incorrectly multiplying the focal length. It might seem trivial, but you see the same mistakes repeated all over the place and people getting into a complete mess. You can use crop factors to estimate equivalent FoV's between different cameras, for example a - 50mm lens on a full frame 35mm camera will give the equivalent FoV to a 35mm lens on a Super35mm video camera because of the approx 1.5 FoV crop factor (50/1.5 = 33), but they are still 50mm and 35mm lenses, one is not the equivalent of the other, it is the FoV's that they provide when paired with specific sensor sizes that are the equivalent.

[Alister Chapman]

To answer the original question: An SD lens with a 2x extender engaged on an EX3 is going to be very soft and is not something I would recommend. Even 2/3" HD lenses on the EX3 tend to perform poorly due to the very small pixel size compared to the pixel size of a 2/3" sensor and the 2x extender makes it 2x as soft. DSLR lenses tend to be a bit more forgiving as they are designed for much higher resolutions.

[Doug Jensen]

. . . and that is why I decided just to exit the conversation yesterday. :-)

[Ronald Jackson]

Maybe I should have said "similar FOV on a 1/2 inch sensor camera". Anyway, answered my question maybe!

So even a 1/2 inch lens with 2x extender likely to be soft? Wonder why Canon/Fuji even bother with extenders if this the case.

I'll probably get GH3 with a 14-140 lens plus a Nikkor adapter as a sort of EX3 backup. Wish Canon had maintained the XL line with something based around the XF305.


Ron

[Alister Chapman]

Nope, FoV's will be different. One lens is 328mm the other is 400mm, noticeably different FoV, crop factor is irrelevant as your not comparing different sensor sizes, you comparing different focal lengths.

Extenders can be useful, but your looking at an SD lens designed for a 2/3" sensor with much, much bigger SD pixels, so it's already at a disadvantage. A 1/2" HD lens with extender should give good performance but they are both rare and expensive.

[Ronald Jackson]

So Alistair, will I get similar "magnification"? The 80-400 at 400 on my EX3 gives me about 40x natural size, maybe a bit more. In "full 35mm terms" (apologies for the un-scientific terminology) this would be via multiplication factor of 5.4, so 400mm (8x natural) becomes 2160, equivalent (40x natural).

Would the 328mm of the B4 lens then become the equivalent of 1771mm with a further "boost" via the 1/2 inch to B4 adaptor of 1.357x to 2460mm equivalent?

At the end of the day I would be looking at a magnified image, on maximum zoom whatever lens I used.
Maybe the quality of such magnified image on the 80-400 will be superior to that on the KJ20 (which a HD lens by the way).

Ron

[Alister Chapman]

No, the magnification will be different, the focal lengths are different. Stop applying multiplication factors to the FL, IT DOES NOT CHANGE, no matter what the sensor size. The 400mm lens will always be longer than the 328mm lens. The 400mm lens will have a narrow FOV than the 328mm lens, so the on screen image will be more magnified with the 400mm, No matter what size sensor you use, 400mm will always be longer than 328mm.

I stand corrected about the KJ20 being HD and not SD.