Help with lense

[laffinorse]

Hello All,

Just bought Cannon 400d lens kit,with Sigma 70-300 F4-5.6 DG APO Macro,
What do the Aperture settings mean, can the lens only be used at these settings.
I have only used it with camera at auto settings, and from the setting info it shows
300mm focal length F7.1 1/400 ISO 400 from about 70yards(see photo under).I am experimenting the other settings TV and AV modes, and want to understand more.

Cheers

[Boddie]

I think you may need to buy a basic photography book Les otherwise this is going to be one painfully long transition into the world of SLR photography. The basics are very much generic but unless you can get an understanding of the basics this subject will really do your head in.

I know Asda had a super book on offer (about £4) last month

[Boddie]

To answer your question though - (provided I have understood it right)

F4-5.6 relates to the maximum aperture that the lens will give you.

Remember that the lower the F number the higher the aperture.

So at 70mil the max will be F4 and at 300 mil the max will be F5.6.

I am not sure what the minimum aperture will be. Could be as much as F40

Effectively the higher the F number (for example 8 being higher than 4), the more of the scene would be in focus.

So if you had two squirrels and one was infront of the other by, for example, 1 foot, if you have the camera set at F4 only one squirrel would be in focus and the other would be blurred. If you set the F to F20 then both squirrels would be in focus.

So remember the lower the F number the less focal length. This is ideal whereby you want only the subject to be concentrated on. When taking pictures of insects for example you want the insect in focus but not all of the surrounding foliage as it detracts from the subject. For landscapes you want as much as possible in focus so a higher F number is necessary.

[Words]

A quick secondary question.

The lens spec doesn't stop you from setting the camera to any f-setting you want, but what I presume the lens spec means is that although you could shoot landscapes with an f4-5.6 lens you'll get better depth of field with a more (or less) specialist lens.

Could someone confirm?

[matt_xyz]

Originally Posted by Words

A quick secondary question.

The lens spec doesn't stop you from setting the camera to any f-setting you want, but what I presume the lens spec means is that although you could shoot landscapes with an f4-5.6 lens you'll get better depth of field with a more (or less) specialist lens.

Could someone confirm?

If I follow you correctly, you're misunderstanding things. An 'f5.6 lens' means a lens that has a largest aperture of f.5.6. Obviously it can be set at other apertures, but 5.6 is its largest. Similarly, some lenses allow you to use an even larger aperture such as f2.8. So, the stated aperture is simply the largest aperture. The larger the aperture of a lens the better it can perform in low light.

A zoom usually has 2 largest apertures depending on the focal length at which you are operating. So a 70-300mm f4/5.6 lens means it has a largest aperture of f4 at 70mm but a largest aperture of f5.6 at 300mm.

hope this helps. Sorry if I've misunderstood and am telling you things you already know

Matt

[Tormentil]

Originally Posted by Boddie

I think you may need to buy a basic photography book Les

Why buy a book, there's plenty of sites on the net that will give you basic facts about photography.

e.g. A Basic Beginners Guide to Digital Photography

[Ollie]

Originally Posted by matt_xyz

If I follow you correctly, you're misunderstanding things. An 'f5.6 lens' means a lens that has a largest aperture of f.5.6. Obviously it can be set at other apertures, but 5.6 is its largest. Similarly, some lenses allow you to use an even larger aperture such as f2.8. So, the stated aperture is simply the largest aperture. The larger the aperture of a lens the better it can perform in low light.

A zoom usually has 2 largest apertures depending on the focal length at which you are operating. So a 70-300mm f4/5.6 lens means it has a largest aperture of f4 at 70mm but a largest aperture of f5.6 at 300mm.

hope this helps. Sorry if I've misunderstood and am telling you things you already know

Matt

I Think Matt is right on this, I used to use this lens before I got the bigma (Sigma 50-500 mm) It's not a bad lens and I took some decent photographs with it.

Just one thing I would like to ask, do you have any problems getting it out of the macro mode. By this I mean getting the macro switch on it back to the telephoto position, because mine used to be a bit stubborn at times. I was always reluctant to force it as I was scared of damaging the mechanism. I did always eventually get it back but sometimes it took several attempts and was very frustrating to say the least.
Roger

[Fourwings]

Originally Posted by Ollie

I Think Matt is right on this, I used to use this lens before I got the bigma (Sigma 50-500 mm) It's not a bad lens and I took some decent photographs with it.

Just one thing I would like to ask, do you have any problems getting it out of the macro mode. By this I mean getting the macro switch on it back to the telephoto position, because mine used to be a bit stubborn at times. I was always reluctant to force it as I was scared of damaging the mechanism. I did always eventually get it back but sometimes it took several attempts and was very frustrating to say the least.
Roger

I can agree with that Roger, I have this lens fitted to a Nikon F65 35mm SLR and yes the macro switch will sometimes appear to jam.
A bit of careful pressure or re-focusing will usually shift it though, that little problem aside it is a very nice little lens and capable of taking nice images.

[Ollie]

Just to give an idea what the Sigma 70-300 F4-5.6 DG APO Macro can do here are a couple of photos I took with mine.



Canon EOS 350D, Sigma 70-300 mm zoom lens, AV mode, ISO 800, F/7.1, 1/400 sec.




Canon EOS 350D, Sigma 70-300 mm zoom lens, AV mode, ISO 400, F/7.1, 1/1000 sec.

Hope these give you some encouragement.
Roger

[Tom Charles]

Hi Les,

Just a follow on from the other answers:

You can shoot with that lens from many different aperture settings. If using it at the 70mm range then f/4 is the widest it will open; at the 300mm range f/5.6.

The 'f' numbers indicate how wide the aperture (pupil) of the lens will open; the lower the f number the wider the opening. Balancing aperture settings and shutter speeds gives you the exposure (amount of light filtered through the lens to make the final image)

In a landscape shot, you generally require the whole scene to be focussed, sharp from front to back, so you close the lens aperture down, make it smaller, say to f/16. Making the aperture smaller this way, requires much slower shutter speeds (slower shutter speeds allows more light to enter the lens) and therefore a sturdy tripod is recommended.

In duller light, especially when photographing a moving subject, eg a bird in flight etc, a lens, ideally will be used 'wide open' thats, in your case f/4 at 70mm and f/5.6 at 300mm, because youre needing to get as much light in a possible and with as fast a shutter speed as possible (to capture the action)

Try and remember this:

The smaller the f/ number (f/4 or f/5.6 in your case) the wider the aperture (pupil of lens) will be; enabling faster shutter speeds (important for moving targets such as birds) but gives a shallower depth of field in focus.

The higher the f/ number (f/8, f/16 etc; which you will have in your lens) the narrower/smaller the aperture (pupil of lens) requiring slower shutter speeds (often used for landscape shots, as it increases the depth of field in focus.

Your camera may do much of the work for you, if you shoot in Automatic or in Aperture or Shutter speed priority mode. These principles will come into play more if you are shooting using full manual mode; here, you need to learn the relationship between aperture, shutter speed and exposure time in order to determine the final image you desire.

Its very exciting discovering these principles. Have loads of fun experimenting!

Tom

ps......understanding film speed also comes into play here; but thats for another day lol