AV on the XT-what am I doing wrong?

[Duncreavy]

My XT is four days old and I have become pretty familiar with most, but not all, of the features. It is my first DSLR but I worked with SLR's centuries ago, before there was automatic anything. So I'm enjoying the upgrade and love the camera but the one that has me puzzled is AV. My understanding is that I can set it to any aperture and the camera will provide the compensating shutterspeed. However, while I can close the lens down, I cannot open it more than F4. Sometimes it sticks at 5 or 5.6. On a hunch I tried the Pmode and it will have the same aperture. If Pmode chooses f4. so does AV. If Pmode chooses 5.6, so does AV. What is it I am not understanding? My manual is dogeared already but I can't figure out what's wrong. Tv seems to be fine. Manual gives me the same problem. I don't even want to think that there is something wrong with the camera so it must be me. Anyone have any ideas? It's probably a simple fix but I'm still a little overwhelmed by the camera. Thanks in advance, Helen

[scraggles]

I may be wrong on the answer, as I'm completely new to cameras, however, I have noticed the same thing on my A80. It tends to happen, based on my zoom level. Does that affect it?

[CRE@TE]

Try zooming it all the way back to 18mm if you are using to kit lense. The more zoom you use, the smaller the apeture will get.

[tommykjensen]

Depending on the lens it has a different maximum aperture (low number) depending on the focal length.

The kit lens is a 18-55 mm f/3.5 - 5.6 which means the maximum aperture at the short end 18 mm is 3.5 on the long end 55 mm it is 5.6 in betwen it varies from 3.5 to 5.6

[Jim_T]

I think I follow you :)

You can only 'open' the lens to it's maximum aperture.

If you have an f/3.5 lens, then that's as wide as you can go. It's physically impossible to select a lower f number.

A variable lens (f/3.5 - 5.6) will open to f/3.5 at the wide end, but only f/5.6 at the long end..

[Duncreavy]

Thank you so much. Yes, I zoomed down to 18 mm and got f.3.5. I just checked and aps. are 3.5-5.6. It's the lens that came with the camera. Now my next question, and I think I know the answer but math is not my strong suit--on the camera dial, while I can't go past 3.5 I can go up to 29. Not sure it really stops down that far, from what you are all saying it doesn't. So that high f stop is a camera artifact and not a true reading? But why would it stick on the other end. Camera is supposed to go to f.2.8--but it is dependent on the lens? Am I making my question clear? I may be mixing apples and oranges but I'm sure someone will straighten me out. Yes?

[CRE@TE]

5.6 is the maximum aperture at max zoom. Meaning, 5.6 is the widest you can have it at full zoom. 55mm

[CRE@TE]

The camera will go to 1.0 if you had a lense capable.

[juneappal]

Aperture is the size of the hole that the light goes through right? That hole is inside the lens, and every lens is built with a different maximum hole size and minimum hole size. I have a zoom lens with max/min of 6.4 and 32. I also have a shorter lens with max/min of 1.4/22. It used to be that the camera mechanically controlled the aperture in the lens. The camera, then had to be built with a max/min mechanical adjustment capacity.
In modern cameras, the camera sends an electronic signal to the lens, telling it how far to shut its own hole. This is handy, because now the camera lens can perform to whatever level it is built, as long as it tells the camera what it is capable of (as far as stopping down.)

[Duncreavy]

Thank you all. I get it.

[prime80]

Thank you so much. Yes, I zoomed down to 18 mm and got f.3.5. I just checked and aps. are 3.5-5.6. It's the lens that came with the camera. Now my next question, and I think I know the answer but math is not my strong suit--on the camera dial, while I can't go past 3.5 I can go up to 29. Not sure it really stops down that far, from what you are all saying it doesn't. So that high f stop is a camera artifact and not a true reading? But why would it stick on the other end. Camera is supposed to go to f.2.8--but it is dependent on the lens? Am I making my question clear? I may be mixing apples and oranges but I'm sure someone will straighten me out. Yes?

Lenses have a maximum and minimum aperture, either variable or fixed. If it's stopping at 29, then that's the minimum aperture of the lens. Your camera will actually go to f1 with the proper lens. All aperture settings are lens dependent on your camera.

[Duncreavy]

Very clear now. I'm sure I knew all of this once upon a time. You've all been so helpful. I'm so glad I found this site. I'll be back for more of your collective wisdom.