Lens focal length versus camera focal length.

[2Hog]

I need help or directions to reading material that would help explain using a lens with a designated focal length in a 10d in which you can set a wide range of focal lengths.

For instance: I have an EF 50 mm f1.4 lens - my 10d allows me to set a wide range of focal settings. What effect does setting the 10d to f5.6 have while using the EF 50mm f1.4 lens? What controls actual focal length?

I would appreciate some help [hopefully I have made myself clear]. Thank You 2hog

[SoCal69]

First off, I think you might want to consider getting a book on basic photography which explains things like focal length, shutter speed, aperature/f-stop and depth of field. Your question seems to be rather involved and probably not easily answered here, although I will try to give you a simple answer below.

From your question, I believe you are mixing up your terms... it seems that you are really asking about the effects on depth of field when changing the aperature/f-stop settings for the lens. You are better off reading up on the basics in a book, but in short, the lower f-stop settings (larger aperatures) result in less depth of field (i.e. more of the foreground and background is blurred). Higher f-stops (smaller aperatures) result in more depth of field.

[2Hog]

Yes Chuck, I believe I have a handle on that.I have some understanding of depth of field and aperature opening. I need help on the relationship of the f stop of the lens and the f stops of the camera and their effects on each other. I guess I need to know - the f stop of the lens is fixed and the f stop settings of the camera are variable [in AV mode for instance] I would expect the aperature to be controlled by the lens. The aperature is in the lens. What is the f stop of the camera controlling? I suspect it is some sort of computer manipulation.

There is something here I do not have a handle on.

2hog

[SoCal69]

Well, then perhaps I don't understand your question. There is only one f-stop setting. The f-stop is simply the size of the aperature of the lens. You change it on the camera (in the old days, you actually set it on the lens), but it is still the lens setting. The camera has no "f-stop." When you are saying 50mm lens with f/1.4, what that means is that the lowest f-stop setting is 1.4. That does not mean you can't change it... in fact, that is exactly what you are doing when you are changing the aperature settings on the camera. I think that should clear up your confusion.

[2Hog]

You got it Chuck. I thought that might be the case. I just couldn't find it in writing. I was under the impression that the EF 50mm F1.4 was fixed at 1.4 and obviously that didn't make sense to me.

I took a bunch of shots and I could see the effects of changing the f stop. I needed to know that the f 1.4 was not fixed but just the lowest setting available. Amazing how you sometimes get hung up on things.

I am finding out that photography for me is going to take time, experience and research.

Thanks 2 hog

[SoCal69]

2hog wrote:
I am finding out that photography for me is going to take time, experience and research.

As it does and will continue to do for all of us...

But of course that is what makes the journey worthwhile! You will have to grace us with some photos soon!

[robertwgross]

2Hog, if you have some good camera equipment, and if you think you have a basic understanding of what's going on, then I would recommend that you take a short course in photography from some local community college. It is possible that they will go over some material that you already think you know. But then, they might teach it in a way that really makes sense and won't be forgotten.

About 25 years ago, I took such a class that was only for five Saturdays. They assigned practice locations for us, and we simply practiced shooting. Then later, we reviewed each others slides and compared. No only can we learn from our own mistakes, but we can even learn from the mistakes of others.

---Bob Gross---

[Mark Kemp]

Another option is to join your local camera / photographic club.

They should have lots of experienced members willing to help and you can usually see lots of peoples work which can also be good.

[Andy_T]

Hi,

you might also find these online ressources helpful:

http://www.agfanet.com/en/cafe/photocourse/classiccourse/cont_index.php3

http://www.dcviews.com/tutors.htm

Have fun,
Andy

[2Hog]

Thanks for all your responses. Hopefully I am on the right track now.

Andy - I looked at the 2 sites you suggested and added them to my favorites for future reading.

Thank You all again 2hog

[scottbergerphoto]

For heuristic purposes, the f/stop is related to the focal length of the lens in the following way: The diameter of the lens opening = Focal length of the Lens / f-stop. Thats why small f-stops have large openings. That being said, lens lengths are not measured in stops, they are measured in mm. Lenses are identified by their focal length in mm and the widest f/stop such as 50mm 1.4 where 50 mm is the focal length and 1.4 is the widest possible aperture (f/stop).