Confusing myself about f-stop and light

[beepbeep]

Hi All,

As an enthusiastic photographer, I recently shot an indoor event for free to gain experience. Many of the photos were keepers, however in a number of them it appears I set the aperture incorrectly and my DoF was too narrow.

I used a Minolta 50mm 1.7 prime for a few shots, but then swapped to a Tamron 17-50 2.8 for the rest.

Now, can anyone explain why the Tamron with a 2.8 max aperture should be any better than the stock Sony kit lens if I don't actually use its better aperture please?

I thought I had all of this nailed down in my head, but it seems to have slipped away!

Cheers,

Rob

 

[Russ77]

Hi All,

As an enthusiastic photographer, I recently shot an indoor event for free to gain experience. Many of the photos were keepers, however in a number of them it appears I set the aperture incorrectly and my DoF was too narrow.

I used a Minolta 50mm 1.7 prime for a few shots, but then swapped to a Tamron 17-50 2.8 for the rest.

Now, can anyone explain why the Tamron with a 2.8 max aperture should be any better than the stock Sony kit lens if I don't actually use its better aperture please?

I thought I had all of this nailed down in my head, but it seems to have slipped away!

Cheers,

Rob

I'm not sure I understand the question, can you clarify what body you were using and what the spec of the Sony kit lens is? In what way was the Tamron better?

 

[Danzaroonie]

You also have to factor in the focal range of your subject and your lens. Your 50mm prime is fixed the Tamron 17-50 is not, so your focal range could change on the Tamron if your not lock at 50mm. Then it depends on you subject distance...all to many factors:bonk:

 

[Johnd2000]

All lenses are better (sharper) stopped down than they will be wide open. Therefore a 2.8 that is stopped down to f4, will generally be better than an, otherwise comparable, f4 used wide open.

 

[beepbeep]

Apologies, on re-reading the question it's not very well worded.

I guess the question is, would the Tamron 17-50 2.8 be better in low light situations than the kit Sony 18-70 3.5-5.6, assuming the same shots were being taken?

If the aperture on both was fixed at F6 for example, would the Tamron still allow more light in therefore giving a faster shutter speed?

I used the Tamron over the Sony thinking that the better aperture ability (2.8 vs a variable 3.5-5.6) would help in this low light situation.

What I should have remembered is that aperture is about DoF. I needed to use a setting that would keep all subjects in focus, and let the camera handle the shutter speed. I did bump up the ISO a bit and used RAW to allow some post production.

Think I've just answered my own question........

Thanks for your responses!

 

[TCR4x4]

The aperture used is the aperture that matters. Weather a lens is fixed throughout the range or changes with zoom is irrelevent.
A f/2.8 fixed lens will be near enough the same as a varible lens at the same aperture say f/8. The only difference you will find is as mentioned above. Most lenses arent their best at thier widest aperture, so an f/2.8 lens at f/2.8 maybe slightly softer than a f/1.7 lens at f/2.8.

For low light shooting, you want a wide apeture, so the Tamron will be better than the Sony, but if you shoot at f/8 you are are defeating the object of using a wide aperture lens in the first place.

In answer to the main question

If the aperture on both was fixed at F6 for example, would the Tamron still allow more light in therefore giving a faster shutter speed?

No. The aperture selceted is whats used at the point of capture.. f/6 is f/6. Although you could get deeply technical and say f/6 is slightly different depending on the focal length/width of lens etc etc, but in laymans terms, F/6 on one lens is the same as f/6 on another, no matter what the lens' maximum widest aperture is.