[Kombisaurus]

Hey guys,

I just ordered a 350D from www.centre.net.au (based in Melbourne), but they won't have stock for a couple of weeks so I'll have worn the carpet bare from pacing up and down waiting that long.

Managed to pick up a *black* one with the lens kit for AU$1469 (RRP $1899). A saving like that is worth the inconvenience of waiting a bit IMHO, as the next closest price I could find was AU$1699 (Cameraland Camera-House here in Perth) and they don't have any in yet either!
It is the "international version" I'm getting, not the Aus version (which is why I could specify a black one), but comes with a world-wide warranty and I've bought stuff from these guys before and they seem straight up.

Just thought I'd post that info to assist any other Aussies who might be shopping for a 350D. I haven't seen any other local prices come close to AU$1469.

Now... my questions about lenses and filters.

As well as the 18-55mm kit lens, I ordered a couple of lenses with the camera to get me started (50mm f1.8 prime and 75-300mm f4-5.6 USM IS zoom). These lenses accept filters with a diameter of 52mm and 58mm respectively, and the kit lens also takes 58mm filters.
I have a bunch of 55mm filters I use with my Oly C750UZ, and I bought a step-up and step-down ring to allow these filters to fit my three new lenses.
Using the 55mm filter on the 50mm f1.8 should be no problem I expect, as it is just a step up from 52mm to 55mm. But initially I thought that using the 55mm filters on the two zoom lenses (that require 58mm filters) would give me a bit of vignetting at the tele-end of the zoom, but they should be no problemmo throughout the rest of the zoom's range.
It then occurred to me that the 350D does not have a full-frame sensor, so it shouldn't need to use the very edges of the lens anyway!! The exact same reason that makes wide-angle lenses less wide on most DSLR's (ie the smaller sensor crops the outside of what would normally fall on 35mm film) should also crop out the vignetting from using a smaller filter on the lens!

Am I correct in this thinking? Can I pretty much expect not to see any vignetting at all from using the 3mm smaller filters on these lenses (18-55mm and 75-300mm).
Obviously I'd expect to see some vignetting if I used them on a film camera, but is there any disadvantage in this approach when all I use them for is digital? Does it mean that I can happily get more 55mm filters and use them on both cameras (Canon and Oly) and all lenses? Or should I try to stick with the correct sized filters for another reason?

I'm also thinking of now modding my Oly C750UZ to be an infrared-only camera (ie removing the infrared cut filter from inside the camera and replacing it with clear glass).
I've read a few websites about this procedure, but I'd be interested to hear from anyone here who has had experience with these kinds of things. I realy enjoy taking IR photos, but when every exposure needs the shutter open for at least 8 seconds (unless you want noisy ISO400 rubbish), it can be quite limiting.

Also, does anyone know where in Aus I could buy a 55mm infrared cut filter? If I remove the IR cut filter from *inside* my Oly, it would be nice to have a "normal" type of lens filter I could screw on to replace when I want to take normal shots too.

Thanks!
Adrian

[StudioJ]

Hey Adrian,

You won't be able to use a circular polarize on the 75-300 it doesn't like them unless you want to manual focus.

PRA stock IR filters but not sure on the size or the price but it wouldn't be cheap.

Good price btw, I'm sure you're going to have fun fun fun until your daddy takes your Kombi away.

Cheers,

The other J

[shuttertalk]

Hey hey! You go, Kombi! I'm sooo excited for yo! (wears carpet out jumping up and down).

Great that you chose the black one.

Hm... your theory about the step up adapter and filter sounds good in theory... I guess you could try it and let us know?

[Rufus]

You won't be able to use a circular polarize on the 75-300 it doesn't like them unless you want to manual focus.

James? :/

[Russt]

half your luck Kombi..........thats a great price for here! I have been checking the price on the 300D and its still up there. Wishing I was flush!


have fun

[slejhamer]

You won't be able to use a circular polarize on the 75-300 it doesn't like them unless you want to manual focus.

James? :/

You lose light with the polarizer. At zoom, the lens at f/5.6 becomes more like f/8 or worse, and the AF system will have problems.

: not James :

[slejhamer]

But initially I thought that using the 55mm filters on the two zoom lenses (that require 58mm filters) would give me a bit of vignetting at the tele-end of the zoom, but they should be no problemmo throughout the rest of the zoom's range.

Opposite: vignetting is more likely at the wide end.

It then occurred to me that the 350D does not have a full-frame sensor, so it shouldn't need to use the very edges of the lens anyway!!
Am I correct in this thinking?

Maybe. The step ring adds space between the filter and lens, and the more you add the more likely you'll get blockage. You won't know until you try it!

I'm also thinking of now modding my Oly C750UZ to be an infrared-only camera (ie removing the infrared cut filter from inside the camera and replacing it with clear glass).
I've read a few websites about this procedure, but I'd be interested to hear from anyone here who has had experience with these kinds of things.

I had my G1 modified by someone who has done many such conversions and was recommended by an acquaintance who had used him. The difficulty is not removing the hot mirror (aka IR cut filter), but in getting the clear optical glass to a precise thickness so that auto-focus is not screwed up. This can involve a lot of trial and error with lots of glass. If you've got access to an optician who can cut glass to various thicknesses (we're talking a millimeter here or there, or fractions of a millimeter) then go ahead and play!

[Kombisaurus]

Thanks guys.. I'm excited! (Big Kev Excited)

Yeah StudioJ, I realised the issue with the circular polariser on the front-focusing 75-300, but decided on that lens anyway. Most of the time I use a polariser is when its on a tripod or I have plenty of time, so manually focusing won't be a big deal, or re-adjusting the filter after focusing. PITA yes, but I wouldn't give up the image stabilisation for a rear-focusing lens... and while the 100-400 L-series IS (rear-focusing) zoom would be the perfect alternative, I can't afford (or justify) another $2.5k, no matter how much I drool over it.

How good are linear polarisers compared to circular ones? I guess it might be worth getting one at some stage if it does bug me, but I'm sure I can live with things until my bank balance recovers from the heart attack it is about to receive.

Thanks also for pointing me to PRA about the filters... I'll see how much I use the Oly once I have the Canon. If I still use it (its a great little P&S with a 38-380 equiv lens - perfect all-rounder for travelling light), or if the Canon lets more IR onto the sensor than the Oly does, then I might just leave it as-is. But if it gathers dust, I'd rather use it for IR photography than sell it I think (unless somebody buys me a 20Da for easter!).

Russt,
If memory serves me, the stand-out 300D I came across was at digital city (http://www.digitalcity.net.au/store/brow...9&brand=21) - they have the 300D Enthusiast kit for AU$1649 which includes the normal kit lens, plus a 55-200 f4-5.6 II USM lens and 256Mb CF card. Looks like very good value if you want the lens (shame the card is only 256Mb though - a bit pointless if you want to take RAW pics).
They also have the regular 300D kit at $1385. While centre.net.au has the regular kit for $1285, theirs is the "international version", but I'm pretty sure Digital City's is the "Australian Version".

Cheers
Adrian

[Kombisaurus]

You won't be able to use a circular polarize on the 75-300 it doesn't like them unless you want to manual focus.

James? :/

You lose light with the polarizer. At zoom, the lens at f/5.6 becomes more like f/8 or worse, and the AF system will have problems.

: not James :

Thanks for the feedback Slej, and for correcting me on the vignetting at wide-angle not tele. <slaps head>
I was wondering about the spacing of the step up/down ring and how it would affect the filter, but I was thinking of it in terms of flare, but of course it would also increase the vignetting problem (if there is going to be one).
Fingers crossed I guess.

But I think StudioJ meant something different when he mentioned the polariser thing.

The problem with a polariser on the 75-300mm lens I ordered and autofocus is not due to the fact you lose about 2 stops of light through a polariser. It is because it is a front-focusing lens, which means the front of the lens (and any filters attached to it) rotate when you focus.
This screws up those filters such as polarisers and grad filters, where the angle they are rotated to is important - as the autofocus just turns them "willy nilly" (there's a phrase we don't hear enough of) just before you take the shot.

A lot of lenses these days are rear-focusing to address this very problem - the focusing is done inside the lens with one of the rear elements, so the front remains stationary.

[shuttertalk]

Regarding the front/rear focusing and polarisers - I thought that was the reason circular polarisers were invented? I'd understand with linear, but circular polarisers were designed specifically to accomodate for rotating lens elements.

[Kombisaurus]

Regarding the front/rear focusing and polarisers - I thought that was the reason circular polarisers were invented? I'd understand with linear, but circular polarisers were designed specifically to accomodate for rotating lens elements.

uh oh.... I think we might be talking about the same thing but calling it different names, or vice versa.

The filter I have sitting my hand right is a Hoya "CIR-POLARIZING" according to the case and 'PL-CIR" is stamped on the filter - and it is mounted on a movable ring that allows you to rotate it while it is mounted to the camera. As you rotate it, you see the polarising effect change.

It is very similar to this one below (but 55mm):

http://cgi.ebay.com.au/ws/eBayISAPI.dll?...eName=WD2V

I assume that can only mean that the polarising filters that are *not* sensitive to the direction they are rotated are Linear Polarisers.

I agree with you ST that it makes sense if the linear polarizers were the ones you rotate and the circular ones were the ones you didn't need to... but the evidence against that is sitting on the desk in front of me, and on eBay. And while I have been known to be wrong in the past, eBay is *never* wrong

Reading the tiny amount of the following article that I can actually make any sense of, it seems the terms "linear" and "circular" refer more to the types of unpolarised light that gets blocked than to way the filters are operated...
http://www.answers.com/topic/polarization-1

Here is a more human-friendly artlcle that explains things in a way that most normal people have a chance of understanding:
http://www.mat.uc.pt/~rps/photos/filters_uv_pol/

FWIW I did the little test with my polarizer in front of the mirror, and it is definately a circular one!

Interestingly though, I forgot about the problems that linear polarizers have with AF systems. I wonder if StudioJ was referring to that when he mentioned the AF issues? I just assumed it was the rotational thing upsetting the filter orientation, but perhaps the auto-focus can't see through any polarizer on that particular lens? hmm.. oh well, I'll find out soon enough I guess.

Cheers
Adrian

ps: Is "polarizer" american spelling, or does the "z" remain for the english/australian spelling as well?

[StudioJ]

I'm not sure whether the failure is due to lack of light or the focusing mechanism of the lens all I know is that it doesn't work in AF!

Mine is currently with a friend in Turkey along with the 28-105 (still love that lens) so I can't test it, the focus would lock on but it was never right.

I mix and match between polarizer and polariser depending on how many Yanks I've talked to during the day.

[slejhamer]

The problem with a polariser on the 75-300mm lens I ordered and autofocus is not due to the fact you lose about 2 stops of light through a polariser. It is because it is a front-focusing lens, which means the front of the lens (and any filters attached to it) rotate when you focus.

That is one problem.

The other problem is that you lose light.

Canon 1-series EOS bodies can autofocus down to f/8. Everything else (D30, D60, 10D, 300D, 20D, etc.) requires a minimum f/5.6 to autofocus. This is a problem whether the light loss is caused by a polarizer or an extension tube or a teleconverter. (Canon even puts a warning on the 2x teleconverter brochure that your lens must be f/2.8 or faster.)

[Kombisaurus]

Canon 1-series EOS bodies can autofocus down to f/8. Everything else (D30, D60, 10D, 300D, 20D, etc.) requires a minimum f/5.6 to autofocus. This is a problem whether the light loss is caused by a polarizer or an extension tube or a teleconverter. (Canon even puts a warning on the 2x teleconverter brochure that your lens must be f/2.8 or faster.)

hmm.. I do remember reading something like that somewhere, but had assumed the AF ability had more to do with available light than aperture.... (as it does with most of the AF systems for P&S digitals). Obviously the aperture, filters, teleconverter and so on will affect the light that reaches the camera, but I thought using a polariser just meant the AF system required more available light to function and would probably fail in low-light where it might still work without a polariser. I didn't give it much thought at the time (as I've been dealing with these issues with a polariser on my Olympus), but maybe I should..

Are you saying that the AF will struggle even in decent sunlight when the aperture is set slower than f/5.6? Or do you mean that as a general guide, the AF will struggle in some conditions with lenses slower than f/5.6?

Obviously a polarising filter will make any AF issues worse, but seeing as I mostly only use them in bright outdoor conditions anyway, I would have thought it would just be like taking photos inside without a polarising filter (ie 2 stops less light). Are you saying things aren't as simple as this?

I used to own an EOS 300 film SLR, but never used a polariser with it. The AF was better (and much faster) than my current Olympus. I'd imagine the 350D would have a similar AF system than the 300 film.

Damn it.. I don't wanna talk about it... I wanna play with it!!!!
<checks mailbox again just in case when they said 2-3 weeks they really meant 12 hours>

[adam]

I hope it magically comes early for you!

When will it be available in the shops here in Perth?
Then I'll be on the lookout for a 350D user driving a bus ! hehe

[Kombisaurus]

I suspect it might already be in a couple of shops here... but only the expensive ones! lol

I'll try to put the camera down when I'm driving my bus... but yeah, look-out!

[slejhamer]

Are you saying that the AF will struggle even in decent sunlight when the aperture is set slower than f/5.6? Or do you mean that as a general guide, the AF will struggle in some conditions with lenses slower than f/5.6?

The latter. The aperture setting is not relevant because the AF system uses the lens at the widest aperture, so the lens' maximum aperture (smallest f/stop number) is all that matters for AF purposes. The lens is not stopped down to your chosen aperture until the picture is taken (except when you press the DOF Preview button.)

So if you have an f/5.6 lens and you cut out two stops of light, the effective maximum aperture becomes f/11. Obviously the lens' real maximum aperture is still f/5.6, but you've reduced the amount of light and made it difficult to see in the dark. Like wearing sunglasses at night.

Going off topic, but related: The change in effective aperture by a polarizer or ND filter does not effect DOF, so for DOF calculations your f/5.6 lens is still an f/5.6 lens. But if you use an extension tube or a teleconverter, DOF will be impacted by both the change in aperture and the change in focal length, e.g., a 200mm f/4 lens with a 2x converter has the same DOF as a 400mm lens at f/8, all else being equal.

Hope that is helpful.

[Kombisaurus]

Thanks Slej,

That has cleared everything up for me! <slaps head again>
I never took into account the fact that all the auto-focusing is done with the lens wide open. Now all the pieces are falling into place.

I was scratching my head thinking "but... I used to take loads of photos at f/22 with my old EOS 300, and it never had a problem with AF?!?!?" but of course it was actually focusing at f/4 or whatever speed the lens was wide open.

What you say about DOF is also interesting, and makes a lot of sense. It's not something I'd really considered with regards to teleconvertors and extension tubes however.

I learn something new every day
Thanks
Adrian

[shuttertalk]

Whoops, sorry to go back into the polariser thing again, but perhaps I should clarify myself.

I have both types - both linear and circular allow you to rotate the filter to get the right polarisation angle. However, linear polarisers affect the AF mechanism on some cameras, in which case a circular polariser has to be used. In doubt, get the circular ones (although they're more expensive)

Are you confused yet?

[Kombisaurus]

Hey ST,

Thanks for clarifying that. I'm not confused at all.. that makes perfect sense to me, and is exactly the understanding I had (that linear filters don't work with all AF systems, and if in doubt, go circular).

The only thing I *didn't* realise was that linear filters are mounted on a rotating ring the same way as circular ones. I've only used circular ones, and never gave it much thought beyond that.

I also thought it was possible to buy polarisers that you didn't have to rotate?
If you imagine a polarising filter as working like lots of tiny little venetian blinds that only allow light passing through them that's coming straight on, I thought the non-rotatable polarisers were kind of structured like lots of concentric circles, a little bit like the hole-saw attachments you buy for drills. Such an arrangement would mean it behaves the same no matter the orientation, although the polarising effect would vary throughout the filter as light hit different angles on the "circles".
I guess I must've added 2 and 2 and got 5, coz I just "figured" that that must be a linear polariser.
Maybe I just had a vivid dream and made the whole thing up? If these type of filters don't exist, maybe I should invent one and make a fortune.. Oh well..

Wow, that's the 2nd thing I've learned from these forums in the last 24 hours (the other being an AF thing in another thread). Can I be excused now? My brain is full.

Thanks
Adrian

[slejhamer]

I also thought it was possible to buy polarisers that you didn't have to rotate?

Yes, they are called sunglasses! Actually, sunglasses are linear polarizers with the polarizing axis in the vertical position.

NOW you may be excused.