Aperture Question

I've noticed (looking in the lens) that, if I am changing aperture settings on my D5100 - it would stay as it was before the change.
But actual aperture will be taken with correct aperture on the pic.
But the aperture will change if I switch from VF to live view and back.

It automatically opens it wide open to get the premium focusing light then when you shoot it stops it down to whatever you set it at or whatever the processor says it should be set at...neat huh?

Thanks Eye-level,
That is the point! If i change it and it did't open wide enough, or close - that would affect the pic?

Well yes...five things affect a snap...aperture, shutter speed, ISO, white balance, and focus plane. You must get a good understanding of these things.

What mode are you using?

Hi Jeff,
That would be M mode.
Since I wasn't sure about that issue - I haven't been changing aperture much and plying with the rest of the settings.
My question - is it normal for D5100 and do you have the same with your camera? or should I send it to Nikon before my warranty is over.
but i have a feeling - there nothing wrong with equipment, it just the way it is..

If you post a few images with exif data we may work it out from them..

What lens?

I think it would be best for you to change to Aperture mode for now. To many variables in Manual mode and unless you really know them backwards and forwards you won't be doing yourself any favors by shooting M. Give yourself a little time here on the forum and myself and others can help you develop a good foundation to understanding the camera. Contrary to what you might hear the D5100 is a very advanced machine and it can do a lot of things. You have to get the fundamentals down in order to grow with any camera. Sounds like you are well on your way playing with M and all! Confidence is a good thing...

Hi Jeff,
That would be Nikkor 18-200mm f/3.5-5.6G VR II DX ED AF-S.
I don't have plans to take photos for living in next few years!
But I think I take good photos just after couple month use of Nikon.

My original question, I didn't get an answer was more about hardware - "is it normal for Nikon to do that"
Thank you for your support

So you are using M mode all of the time? I am not familiar at all with AF lenses. I have one but I still haven't really used it but I have used other ones many times just haven't studied them close enough to see what the aperture is doing when I am changing things around. I would assume that your camera is OK if your pictures are OK. Try holding the shutter button halfway and see if that changes the aperture. Someone else may have to help you with this question. With that lens everytime you focus it should be within it's range 3.5-5.6 wide open...then when you trip the shutter it should stop down to whatever stop and speed you have manually set it to. Like I said I doubt there is anything wrong with the camera or lens.

Thanks Jeff.
guess - I just need to get a second D5100 in my hands to see what is going on.

i really did not understand the question

Thanks anyway... I will just go to store, put two D5100 next to each other and see.