Sig 800mm prime vs Sig Monster

I was wondering if the guys on this forum with the above lenses could give me some idea of the image quality - especially the 500mm to 800mm quality of the Sig Monster.

I was contemplating a nik 600mm to add to my 300 & 500 Sig primes but then I have a problem with £6K for half a stop gain over my 500mm 4.5 and 20% mag increase - the half stop is pretty meaningless, and 20% isn't much for 6 grand.

Ordinarily I'd go for the 800 prime but I would use the lens on my XL2 video camera aswell so the zoom capability of the Sig Monster has great theoretical appeal, not just for image composition but also for subject aquisition - 800mm equates to nearly 6400mm when its dropped on the front of an XL2 - try finding a wren in brambles with that one unaided

I've no first hand experience of either lens but I would expect the 800 prime to be as good as my existing 500mm resolution-wise, Sigmas MTF charts show that it is on paper at least.

Thoughts on both lenses gratefully appreciated guys

Regards

Andy

Hi the 300-800 is slightly sharper throughout its focal range wide open than the 800 prime but by one-third of a stop down there is very little difference and from the couple I have used by f7.1 indistinguishable, the image quality is very constant throughout its Zoom range.

Phillip.

Andy, I could be wrong but, I think John Swift has a Sig Monster in Nik fit for sale.

correct me if i'm wrong but doesn't the xl2 use a EF mount. Having used a 400/2.8, 600/4, and now the sig monster on a canon 20D, i must say that at f8, they're all the same. In fact, i found myself shooting so much at f7.1 i could justify selling the 600 and 400. If you find yourself shooting wide open all the time, then the primes are the way to go as they really excel there and stopped down 1 stop. But truly sigma has gotten it right with the monster. It is superb at 5.6 (depth of field is paper thin though) and by f8, wow is all i can say. My gallery (http://szekiat.zoto.com) has lots of nature pics all taken with the monster and some with a 1.4x TC even, or better still check out romy ocon's work (the original sigmonster master if u ask me: http://www.pbase.com/liquidstone)

Hi Szekiat - XL2 does not have an EF mount - Canon produce an adaptor for the fitting of their EF lenses which is rather expensive and couples with the autofocus and IS.

I use Nikon fit lenses via an Optex adaptor - I don't want the AF or IS to even attempt to work at these degrees of magnification.

Thanks for the input though, and to Phillip & Tom

Looks like I shall be purchasing a Sig Monster at the earliest opportunity

Regards

Andy

If it matters at all, have you checked the size/ weight trade-off? The prime is 24cm shorter and 1.1kg lighter. This basically means adding a full-size 300/4 to the lens size/mass if you go with the zoom. The zoom has a shorter minimum focus distance, though (6m vs 7m).

(no real experience with monsters, so it`s all theory from me)