Dumb newbie

[ncrick]

Hello folks, I am brand new to this forum. I am a new owner of a 300D Canon digital Rebel. I am certainly not new to photography but am nothing more than a hobbieist who is compositionally challenged. I hope I am not rehashing a question asked many times before but I have read through a lot of the posts with out having seen this question come up before: I understand the additional magnification that I will get by adding a 70-200 MM f4 zoom lens to my camera but I wonder if it will still be an f4 lens? With the smaller image sensor area will less light be “picked up” and reduce the speed of the lens? My little brain cant quite comprehend how this works but I am thinking it will stay f4.

Thanks in advance for your help!

[jseah]

f4 will still be f4

[pstewart]

Hi, Ncrick! I just got a new Rebel 300D also and have the 75-300mm lens. I am a bit lost on a lot of the controls. I will have to read the manual at least three times I think! Too much to absorb and not much time to try it all out. Good luck with yours and post some pics soon! I have only one gallery so far that used the new camera: http://www.pbase.com/pstewart/antique_store All my others are from scans of old pics. I am delighted with how well and quickly this camera works, but I am overwhelmed at how much learning I have ahead of me.

Phyllis

[ncrick]

Hi Phyllis,

I love your photos. I am afraid that all the features in the world wont help me point the camera at the right thing! I really have not had too many problems learning the camera. All the fully automatic functions are just that. I hate that there is no aperture setting on the lens, the contortions needed to adjust both shutter speed and aperture in the full manual mode. This is my first auto focus SLR and I have to wonder if is that much of an advantage under well lit conditions. I’d give up the built in flash for a PC socket! The image quality is great! The Raw image format makes it take a while to down load using the utility they send with the camera. Photoshop Elements wont read the RAW image directly. The biggest JPEG setting seems just as good for any way I have of looking at the photos. I have been using parameter 2 for color balance and I like that better than the standard parameter 1. I want to play with Adobe RGB sometime. This color management still is a real challenge for me. If I ever can get my monitor and printer to match the actual object, I will be happy!

Can any one tell me why the lens speed stays the same even though less of the lens is used with the smaller than 35mm image area?

Rick

[pstewart]

Hi Phyllis,

I love your photos. I am afraid that all the features in the world wont help me point the camera at the right thing! I really have not had too many problems learning the camera. All the fully automatic functions are just that. I hate that there is no aperture setting on the lens, the contortions needed to adjust both shutter speed and aperture in the full manual mode.

Thanks, Rick. I never really thought about this, but it is something to get used to, isn't it? I only took three pics with the long lens so far, so I didn't notice.

For my main lens I bought the Sigma 28-80mm and it doesn't have a way to set aperture on the lens either. You have to read it on the camera and adjust it there. Is this to make the lenses cheaper? Or will this camera only use lenses that don't have aperture rings but have to be adjusted through the camera instead? Hmm...I just looked and the new Sigma EX 15-30mm lens I just got in the mail today does have separate aperture numbers on the ring. It's in a higher price category I think. Is that why, or is it because it's a wide angle lens, or what?

Interesting question. I haven't felt a need to use manual mode yet so wouldn't have noticed this if you hadn't pointed it out!

[castledude]

As a simple thought problem.

Imagine you take a picture then get back a strip of film you then cut an individual frame into 4 pieces. Obviously the fstop for each quarter frame is no different from the overall picture. This is because the fstop is (effectively) the amount of photonic energy hitting a spot. It is not a measurement of the energy over the entire area.

This is also why you get a magnification since if you blow up the 1/4 piece of film to a common size (lets say 5 by 7) you will have less information spread over a larger area giving you a magnification.

--------------------
For those nitpickers I do know that fstop is actually the numerical value of the relative aperture. If the relative aperture is f8, 8 is the f-number and indicates that the focal length of the lens is 8 times the size of the lens aperture (quote blantently stolen from an online dictionary)

[ncrick]

Thank You castledude, for the outstanding answer. I get it!