Thanks again all or your input.
Brett the 650 is the model I'm using now. I am having trouble using adapted lenses with it.
Maybe I need to try an older chipped adapter.
By chance I did buy an RT although it's not here yet. I sure looks like an interesting beast!
I wonder if there resolution loss from the mirror glass between the lens and the film.
It must at least loose some light. What should one expect -1/2 stop loss or so?
Lynn your Portraits are always a joy to view. I'm going to stick with the lowly 50mm f1.8 for as long as I can handle the racket it makes while focussing.
One thing I do like about the nifty fifty is the tactile feel of manual focusing.
It's not a silky as a real manual focus lens but, the focus ring does give some feedback.
Gavin your comments on the f2/100mm are very encouraging. I hope I like it as much as you do.
Years ago I owned a Sigma f1.4/30mm for my 40D. This was a DX lens.
I really liked the materials and build of that lens. I imagine the Sigma 50mm f1.4 has a similar build.
I'll keep my eyes open for deals on that lens as well.
Luckily 50 and 100 are my main FL's for SLR cameras.... Trying AF lenses now will not change that.
Cheers!
Hi,
The RT is a very technically interesting design. The pellicle mirror reflects about two thirds of a stop of light through to the viewfinder, at the expense of light hitting the film plane. It excels at many things, but for really low light work the 630 it is based on is a better option, or indeed a 650, 620 or EOS-1. The basic control layout of the later EOS models 620, 630 (600) RT are all identical to the 650 (except that the 650 lacked the multiple exposure button on top left of the body the later ones have). There are also custom functions that can be set on the later types, but as far as the business of making images goes you would be hard pressed to notice which one is which in use as they handle identically.
To exploit the near instant response cabability of the RT, the on/off switch has to be turned anti-clockwise to "RT". The difference between "RT" mode, and the normal mode of operation shared by the EOS models equipped with "normal" mirrors is that with the dial set to "RT", once focus confirmation is made, the aperture stops down to the pre-selected f stop, so that when the button is depressed the only thing the mechanism has to do is actuate the curtains. If the attached lens is not being shot wide open, the viewfinder will dim a little (or a lot, if the lens is stopped right down), but, you enjoy uninterrupted vision through the finder during the exposure. The most impressive aspect is pressing that button in RT mode, the shutter response is fast as lightning.
The RT also has the "normal" non-RT mode of operation that you can select (rotate the main switch clockwise). In this setting it behaves exactly like Eg. the EOS 650. The reason for the normal mode of operation is that, with the main switch set to RT mode, servo focus tracking isn't available but in the normal setting, it is.
Re: loss of resolution, according to the wikipedia article on the RT, Modern Photography opined a loss of sharpness from the pellicle mirror. In normal use, I don't think you would consider it a factor, I've used my 650, 620, 630 & RT interchangeably, and I've never noticed a difference. I'd be interested to read the review in question though. The same mirror introduced in the RT was subsequently used in the EOS-1N RS, a camera that found popularity with professional sports photographers, so personally I wouldn't worry. On the plus side, for tripod work the RT has an added benefit of a smoother shutter action because that fixed mirror means no mirror slap. There is a very small sub-mirror assembly for focus or metering purposes, (I forget which) that must retract prior to exposure (in RT mode it does this once focus has been achieved, before the shutter releases). It's tiny, and adds very little vibration indeed to the mechanism, (you can see it flip up if you fire the camera unloaded, with no lens fitted). As a result the RT has a smoother mechanism than other EOS models with conventional mirrors.
The RT pellicle mirrors age well. Providing owners have kept their fingers away from them they seem to age very well. It's good to be careful swapping lenses in dirty conditions of course, as you want to keep that mirror as clean as possible. But you can give it a gentle blow clean with a blower, and I've even cleaned mine a couple of times, (very carefully) with no ill effects at all. They're fragile, and demand respect, but are not nearly as fragile as some would have you think.
Cheers,
Brett
