lens(es) question(s)

panocho · Mar 24, 2005

So I bought this lens for my recently adquired Canon A1. I wanted a zoom to complement, and I went for a Cosina 80-200 f4.5 -I just couldn't afford any other thing, as since I won't be using it very much, it sure can satisfy for a while. Someday I'll upgrade.
I received it yesterday, and found something strange, which I want to ask you about. The thing is that, after shoting, the aperture remains at f5.6 (the lens is f4.5). Obviously, this affects the visibility through the viewfinder. Then, trying to find out about this, I noticed that the aperture seems to open again completely when I wind.
Well, I just wanted to ask you if you have some idea about what could be happening here. It doesn't seem to be a big problem (is it a problem at all?), but still...
Next time I'll try to save and buy better lenses. They are the most important part of all, aren't they?

By the way, and making two threads in one (sorry!), what do you think in general about zoom lenses? I know many people don't like them at all, and although I always thought that was exagerated, I begin to suspect it may be not. I have not been really satisfied for a long time with the results of my Nikon AF 35-70mm f3.3/4.5 (well, I blame the lens... maybe I'm wrong?), and that long time I have been thinking on getting rid of that lens and start with a 50mm. I like that crisp and clear images and I just don't get them... Any opinions on this?

ksmattfish · Mar 24, 2005

Typically a lens remains wide open no matter what the aperture is set at to help with focusing. It closes down to the set f/stop right before the exposure is made, and then opens back up again to wide open. It's possible that the lens you have doesn't open back up until the camera is cocked.

In the past primes were probably sharper than zooms, but most modern zooms (modern meaning designed and built after 1990) are just as sharp as a prime lens. I don't know when your lens was built, and even if it was built recently, it might be from an older design since it's for the older Canon FD mount cameras.

Christie Photo · Mar 24, 2005

I had this happen with an old Pentax. That lens operated by use of a pin which was employed while meeting and making an exposure. A plate would rise up at these times, depressing the pin which in turn would stop down the lens. This is an old screw-mount camera, and evidently I changed lenses while the meter was on, which had engaged the plate, causing the pin to bend a bit when I turned it onto the camera.

I don't know if your camera work like this. I hope this helps.

-Pete Christie

panocho · Mar 25, 2005

ksmattfish said:
In the past primes were probably sharper than zooms, but most modern zooms (modern meaning designed and built after 1990) are just as sharp as a prime lens. I don't know when your lens was built, and even if it was built recently, it might be from an older design since it's for the older Canon FD mount cameras.

The lens I was talking about was not the Cosina for Canon FD, but a Nikon AF (sorry for the confusion, I just mixed to threads in one). This Nikon AF was very likely built after 1990. Also the Canon EF's that appear on this thread must have been built after the 90's (see pics of a Canon body below in the thread):
http://www.thephotoforum.com/forum/showthread.php?t=18821
And there is a clear difference, isn't it? This is precisely what I suspect might happen if I changed my Nikon AF 35-70 f3.3/4.5 for a 50mm -to start with.

Mitica100 · Mar 25, 2005

panocho said:
So I bought this lens for my recently adquired Canon A1. I wanted a zoom to complement, and I went for a Cosina 80-200 f4.5 -I just couldn't afford any other thing, as since I won't be using it very much, it sure can satisfy for a while. Someday I'll upgrade.
I received it yesterday, and found something strange, which I want to ask you about. The thing is that, after shoting, the aperture remains at f5.6 (the lens is f4.5). Obviously, this affects the visibility through the viewfinder. Then, trying to find out about this, I noticed that the aperture seems to open again completely when I wind.
Well, I just wanted to ask you if you have some idea about what could be happening here. It doesn't seem to be a big problem (is it a problem at all?), but still...
Next time I'll try to save and buy better lenses. They are the most important part of all, aren't they?

Panocho, is this lens an FD mount or FL? Cosina made decent glass, not your best and sharpest but decent. Also, does it have the "A" (for Automatic) stop on the aperture ring? If so, make sure it's engaged in that "A" position. Another possible cause would be the DOF preview situated in the lower right corner of the camera, as you look at it from the front. Make sure it's not engaged. Just a few ideas... Let me know if it helped. :mrgreen:

panocho · Mar 28, 2005

Thanks for the suggestions, but I'm afraid it's neither of them.
It's a FD mount, with A setting. Doesn't matter whether I set it in A or manually select some other aperture. And the DOF button is not engaged.

I thing I'll just forget about it, since I comproved that it does open when I wind the film, so there's no problem, after all. It is strange, though.

Thanks for all your suggestions. I'm glad to know about Cosina decent quality.