Why do people recommend f2.8/f2.0 etc

[Barks]

Time and time again I've read review of f2.8 lenses where they're 'great for indoor/low-light photography' etc.

I've got a 550D and a Tamron f2.8 17-50mm. I've also owned a Sigma f2.8 Sigma 24-70mm.

So both were fantastic lenses in bright conditions and outdoors. Both were utterly hopeless at family events/parties etc where I really wanted to take decent shots.

Left in Auto mode, the camera automatically jumps straight to f2.8. Due to the depth of field it virtually almost always focuses on the wrong thing leaving the rest of the image blurred (yes I've tried different focusing options) and usually if there's a portrait where one person is even half a metre out from everyone else, they will be completely out of focus.

If I put the camera in AV and select, say, f4.0 - which is safer - it puts the shutter time to about 1second even with flash on. If I put the shutter time to 1/60 - it puts the aperture to f2.8 and we're back to square one.

In these situations you just want to hand people the camera so they can quickly and easily take photos. I shouldn't have to goto manual mode and set aperture/ISO and shutter.

Is there anyway of telling my 550d in automatic mode to AVOID going below f4.0? This is the sole reason my next lens will be an L f4.0 and not an L f2.8.

Cheers

 

[Barks]

Thanks for the replies.

Some of you have inferred that I don't have an understanding of Shutter/Iso/Aperture. I don't think this is fair, I have a solid understanding of these and I never usually shoot in Auto mode. My point was more to do with the fact that you can't just hand an SLR over to a family member and expect a decent photo in the same way you can with a P&S. I think the answer to this question is you can depending on the lens but you certainly can't with an f2.8. If you think how many people buy SLRs and shoot in Auto the whole time - because they're fashionable or whatever (I have loads of female friends around my age group 20-25 who have SLRs and no clue about photography including my misses).

I'm fully aware that:

- As you increase the ISO the sensor becomes more sensitive at the sacrifice of image quality.
- The shutter speed is essentially how long you expose an image for. So 1/500 would be suitable for an action shot, 1/60 suitable for a portrait, and long 10-15second exposures for experimental shots in different lighting conditions.
- A larger aperture (f2.8 for example) results in a smaller area of the image being in focus. Using a smaller aperture you can expect more of the image to be in focus.

 

[Barks]

Also I appreciate the advice/tips. Sorry if my original post was a bit grumpy, had a bad morning

 

[Barks]

No, I believe the complaint is that if you gave a person who has a DSLR but doesn't really know how to use one, or even just handed it to a family member at christmas so they could take a photo, then it wouldn't get as good results on auto as a point and shoot would if you're using a f2.8 because in low lights the camera will automatically shove it down to f2.8 and have a very shallow DoF.

I think that's roughly what you've clarified with?

If so, then that's one of the inherent problems of a DSLR, and in fact any incredible tool. If you don't know how to use it properly, the chances are you won't get a good photo.

Your average joe also probably won't invest massively in lenses, and will happily stick with their kit lens as well. Something that likely won't create these issues as much, because they won't go as wide.

kd

Spot on.

From experience of my Nikon and Canon SLRs - Anyone can shoot in Auto with the kit lens and get great looking photos. As soon as you move onto specialised lenses you lose the ability to P&S and still get solid results.

So I guess as a conclusion from this thread. In future I'll put it in manual mode with a high max ISO and set it at, say, 1/60 and f4.5 with spot metering on. Hopefully this way I'll be able to pass it around and still get good images.