«

Hi, all.

I'm looking at options for my new Rebel 300d.

I am considering Canon's 75-300 IS lens. I expect it would be a good
choice.

I see an inexpensive 2x telephoto out there, from a company called
Digital Optics. this would give me 900mm effective (yikes!).

Does anyone know about this crew's lenses? It's certainly a low price
point ($60 for the 2x), so I am suspicious of the quality. On the other
hand, it's cheap enough that it might just be worth getting for kicks.

But some precedent on Digital Optics' quality would be useful.

Any wisdom out there?

Thanks!

DW.

"BD" <> wrote in message
news: ups.com...
> Hi, all.
>
> I'm looking at options for my new Rebel 300d.
>
> I am considering Canon's 75-300 IS lens. I expect it would be a good
> choice.
>
> I see an inexpensive 2x telephoto out there, from a company called
> Digital Optics. this would give me 900mm effective (yikes!).

"Yikes!" is right, but what on earth would you use a 900mm (equiv.) lens
for? Do you have any idea of the problems you'd have using such a lens, even
in the (unlikely) case that such a converter could produce acceptable image
quality?


>
> Does anyone know about this crew's lenses? It's certainly a low price
> point ($60 for the 2x), so I am suspicious of the quality.

And rightly so.


> On the other
> hand, it's cheap enough that it might just be worth getting for kicks.

Yes, or you could just put the $60 in a shredder and save yourself the
bother and wasted time.


>
> But some precedent on Digital Optics' quality would be useful.
>
> Any wisdom out there?

No experience with that <ahem> brand myself, but I would be leery of any
such attachment that's essentially a no-name product. First, would it even
fit that 75-300mm lens? Most of those kinds of converters are threaded for
37mm or 52mm attachment. I'd be surprised if any 75-300 has a filter size as
small as 52mm.

Here are some comments from others on the "Digital Optics" (aka "Crystal
Optics") brand attachments:
http://www.stevesforums.com/forums/v...61&forum_id=50

I strongly suggest you get the 75-300 first and *then* decide if you really
need or want more focal length. In any case it seems unlikely to me that any
front-end converter would be suitable for such a lens.

N.

Yeah, I tend to agree. But I do have a mild 'astral protography' bent,
and if I could spend $70 more to get some insanely large moon shots
(who cares about corner/edge problems on a moon shot), That alone might
be worth the price of admission.

But yes, I think starting with the 300 would be wise regardless.

"2X telephoto...900mm effective" You are quite confused, it sounds.
In order for 2X to provide 900mm effective, you have to start with
450mm!!! Put it in front of 80mm, and you end up with something
similar to a 160mm lens.

Digital Optics is an example of a way to take a non-interchangeable
lens and extend its focal length. It mounts on FRONT of the existing
lens. Since you have an SLR, you don't want that! You want to use a
'teleconvertor', and most are 2X in effect like the 2X front-mounted
unit but generally better in quality of result.

--wilt

I will admit to being confused, as I'm only starting to get my head
around the vernacular. the 900 effective comes from:

Native lens length = 300
Teleconverter = 2x => 600mm
x 1.6 to 'translate' from 35mm to digicam equivalent => ~900mm.

I'm not intentionally talking out of my arse or being obtuse, I'm just
at the start of a bit of a learning curve.

the 1.6 multiplier comes from (I nicked this from another post)
...."reduced sensor size results in a 50mm lens
having the same field of view as an 80mm lens"

"wilt" <> wrote in message
news: ups.com...
> "2X telephoto...900mm effective" You are quite confused, it sounds.
> In order for 2X to provide 900mm effective, you have to start with
> 450mm!!! Put it in front of 80mm, and you end up with something
> similar to a 160mm lens.

I think the camera in question was a Rebel-D, so unless Canon has made a
one-off Rebel-D with full sized sensor the 900mm is quite close. True reach
would be somewhat greater than 900.

At the long end of his zoom he'd get 300 x 1.6 = 480. And the 2x would net
him 960. Admitedly it is probably a very crappy 960, but you were only
addressing the overall math.....a point on which he was correct.

In article <. com>,
"BD" <> wrote:

> Hi, all.
>
> I'm looking at options for my new Rebel 300d.
>
> I am considering Canon's 75-300 IS lens. I expect it would be a good
> choice.

It's great. I have one for sale if you are interested.

>
> I see an inexpensive 2x telephoto out there, from a company called
> Digital Optics. this would give me 900mm effective (yikes!).
>
> Does anyone know about this crew's lenses? It's certainly a low price
> point ($60 for the 2x), so I am suspicious of the quality. On the other
> hand, it's cheap enough that it might just be worth getting for kicks.
>
> But some precedent on Digital Optics' quality would be useful.
>
> Any wisdom out there?
>
> Thanks!
>
> DW.

--

http://home.nc.rr.com/christianbonanno/

"wilt" <> wrote in message
news: ups.com...
> "2X telephoto...900mm effective" You are quite confused, it sounds.
> In order for 2X to provide 900mm effective, you have to start with
> 450mm!!! Put it in front of 80mm, and you end up with something
> similar to a 160mm lens.

Where'd you get that 80mm, though? He's asking about putting the 2x
converter on a 75-300mm lens. Given the Canon's 1.6x focal length factor,
that works out to 960mm effective equivalent. Close enough, since these
numbers are approximations anyway. (The 75-300 is probably a bit less than
an actual 300mm at the long end, the 1.6x factor is just an approximation,
and the 2x conversion probably isn't exact either.


>
> Digital Optics is an example of a way to take a non-interchangeable
> lens and extend its focal length. It mounts on FRONT of the existing
> lens. Since you have an SLR, you don't want that! You want to use a
> 'teleconvertor', and most are 2X in effect like the 2X front-mounted
> unit but generally better in quality of result.

Right, but the problem there is that the rear-mounted 2x tele extender will
cut his maximum aperture by two stops, at which point his SLR will no longer
autofocus. I.e., if his 75-300 is f/5.6 at the long end it will be f/11 with
a 2x extender, too small an aperture for the SLR to autofocus (perhaps even
too small for it to be readily manually focused).

That is in fact the one advantage to a front-mounted converter: it won't
change his maximum aperture, provided it's designed so as to be suitable for
that particular lens. (Which in this case it almost certainly isn't,
however.)

N.

In message <. com>,
"BD" <> wrote:

>Hi, all.
>
>I'm looking at options for my new Rebel 300d.
>
>I am considering Canon's 75-300 IS lens. I expect it would be a good
>choice.
>
>I see an inexpensive 2x telephoto out there, from a company called
>Digital Optics. this would give me 900mm effective (yikes!).
>
>Does anyone know about this crew's lenses? It's certainly a low price
>point ($60 for the 2x), so I am suspicious of the quality. On the other
>hand, it's cheap enough that it might just be worth getting for kicks.
>
>But some precedent on Digital Optics' quality would be useful.
>
>Any wisdom out there?

Yeah. Don't get that lens if you want to use a teleconverter. It's not
sharp enough to get any more detail out of it; it is already pushed to
its limits without a TC.

Also. you really should stop multiplying focal lengths by 1.6. That
zoom with a 2x is 600mm, not 900. It will have about as much detail as
a really sharp 200mm lens on a full-35mm-frame camera.

There's no free lunch or magic with teleconverters; they waste light,
and light isn't worth wasting unless you gain something from it.
Teleconverters are for sharp, top-end lenses, not budget consumer
lenses.

Also, the better TCs start at about $200.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><