Is F2.8 really beneficial over F4?

mrbez

mrbez

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Hi Guys,

As the title asks, is F2.8 really beneficial over F4?

I'm talking about the 17-55 2.8 or the 24-105.

What would the different in shutter speed be between the two?
 
Yes.

One stop difference.
30th @ f/4
60th @ f/2.8
 
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Arkady said:
Yes.
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:thumbs: What he say.

Double the light through the lens, half the time you open the shutter.

I can't think of a time where a faster lens isn't a better option, given everything else is even. You also get a brighter image through the finder and the option of shallow depth of field.

That's quite a difference in focal range there too, so you need to take into account which serves you better.
 
So the difference is that the shutter speed will be twice as fast with 2.8 over 4?

If I have a 50 1.8, this will be twice as fast as the 2.8?

Surely a 24-105 with a 10-20 would be better then?
 
320px-Aperture_diagram.svg.png
 
Are you sure that's not just a 1.4 lens getting further away? :)
 
Also, lenses tend be sharper slightly stopped down so a 2.8 lens stopped down to f4 is likely to be sharper than an f4 lens wide open.

Oh and yes, the shutter speed will be twice as quick at f2.8 compared to f4.
 
not twice - it's one stop of light difference . as well as iso200 vs iso400 etc.


f1.8 vs 2.8 is more than one stop, but too lazy to think how much, digital has spoiled me with those silly non original stop numbers.
 
Starastin said:
not twice - it's one stop of light difference . as well as iso200 vs iso400 etc.


f1.8 vs 2.8 is more than one stop, but too lazy to think how much, digital has spoiled me with those silly non original stop numbers.
Click to expand...

One and a third...
 
makes a huge difference,just bought a 24-70 2.8,to replace the kit lens,that and the nifty fifty 1.8,as said when you stop it down by a stop ,image quality is always better.the 1.8 lets me take some lovely images indoor with out flash, defiantly an eye opener when you first use it.The 2.8 lets more light in when focussing/viewing in camera
 
All depends what you are going to use it for.

Apart from shutter speed the main benefit of a 2.8 over f4 is a brighter viewfinder and slightly better AF depending on what camera you use.
I would say it used to be really important when we all shot film but as highish iso is so good these days, save your money.

All my lenses are 2.8, and I can't remember the last time I shot anything at 2.8, most of my environmental portraits are done at 400-800.
 
Yes it makes a big difference, this time round I avoided kit lenses completely, the only lenses I own slower than F2.8 are those that are pointed at a bright sky and only owned because I cannot manage the weight of the F2.8 equivalent.

Currently I really want a 10-22mm but all are F3.5 or higher so I'm not bothering.
 
I'd say it depends what you're using it for. On the whole, yes, for the reasons above, but if the size/weight of a f/2.8 lens mean it's sitting on a shelf collecting dust rather than being used, then obviously the f/4 version would be better for you!
 
all my lenses bar one are f/2.8 or faster. why - i do a lot of indoor stuff with only ambient lighting and little time to faff about.

If its just a walkabout, go for the focal length over the f/2.8. the 24-105 has IS to help keep a steady shot. However the focal length is not very wide on a crop body but you have said you have the 10-20mm any way and its up to you if that 4mm is going to be in the range you use most.
 
Aside from the benefit of shutterspeed, you also get the option of a shallower depth of field which helps if you have a cluttered background or your want to make your subject stand out more.

If you can afford it and are not worried by the extra weight then go for the 2.8.

If funds are tight or weight is an issue the 24-105 is a great lens....possible a more suitable walk around lens depending on what you shot. I have the 17-55 f2.8 and do find I often wish for more reach.
 
If you can afford it and need a faster shutter speed then yes it is worth it.
If you are a casual shooter then maybe not.
 
I suppose the answer is yes and no.

If I do a quick compare of two lenses I have, the 70-200 F4 and the 70-200 f2.8 IS, then the 2.8 lens allows one stop more of shutter speed and the narrow depth of field can really pull the subject out from the background, but it's also a much bigger, heavier lens.

I also have the 24-105 IS lens as a walkabout - brilliant lens with a good range of zoom. I decided on this over the 24-70 f2.8 because of the range and the 24-70 was 50% heavier.
 
I had a practical example the other week, I normally have a 24-105 F4 on a 5D. I was in a local theatre so no flash allowed; I tried the 24-105 F4 but could not get the results I wanted,either too noisy or too blurred for the dancers, in the end used an 85mm 1.8 (at 2.8) and a 50mm 1.8 (at 2.8). The ISO was in the range of 800 or 1600, depending on shutter speed required (dance etc). I see where your coming from, it can be a lot of cash if you are not going to use the aperature very often, its just that sometimes there is no option; I will update my 50mm to the 1.4 but will not be buying L glass at 2.8, as I personally will not get the benefit often enough.
 
dazzajl said:
Are you sure that's not just a 1.4 lens getting further away? :)
Click to expand...

Father Ted: Now concentrate this time, Dougal. These
[he points to some plastic cows on the table]
Father Ted: are very small; those
[pointing at some cows out of the window]
Father Ted: are far away...
 
Taking a shot at F2.8 with a F2.8 lens you are in the danger zone at the near periphery of the lens. Stopping down to F4 is far better. But you cannot expect an F4 lens to be its equal,as it is at F4, its max diameter.
 
classcams said:
Taking a shot at F2.8 with a F2.8 lens you are in the danger zone at the near periphery of the lens. Stopping down to F4 is far better. But you cannot expect an F4 lens to be its equal,as it is at F4, its max diameter.
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So are you saying that all those 2.8 lenses can't shoot at widest aperture?

If the lens is designed properly then there is no problem shooting wide open.

In fact my 1.4 50mm is pin sharp wide open.
 
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The two lenses you have selected (17-55 & 24-105) are quite different. On your crop sensor body, the 17-55 is similar to a 24-70 on a FF body. The 24-105 although slower, gives you more range. For a walkabout I have found that the 17-55 is excellent, and keep my 70-200 in the bag just in case I need the extra focal length. Both lenses have IS.

Although not an "L" lens, the 17-55 f2.8 is very well made and performs excellently well. If you're looking to do portraits you may find the longer lens a better option.

Steve
 
PsiFox said:
So are you saying that all those 2.8 lenses can't shoot at widest aperture?

If the lens is designed properly then there is no problem shooting wide open.

In fact my 1.4 50mm is pin sharp wide open.
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I advise you to check PHOTOZINE for the resolution of both Nikon and Canon to see how the 50mm f1.4 degrades at both centre and border at F1.4.
 
So how about if you are shooting at f8, which is stopped down on both lenses. Would the f2.8 still give noticably better image quality than the f4?
 
Cris_L said:
So how about if you are shooting at f8, which is stopped down on both lenses. Would the f2.8 still give noticably better image quality than the f4?
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maybe not but around f8 most lenses are near their sweet spot. If thats all he needs is something at f8 then there are plenty of other cheaper lenses for his needs.

One thing though, he will still have a brighter viewfinder with the f/2.8
 
Cris_L said:
So how about if you are shooting at f8, which is stopped down on both lenses. Would the f2.8 still give noticably better image quality than the f4?
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The gap will narrow but I can see a difference between shots taken with a 24-70 and those with a 24-105. The 24-70 are better by the way ;)
 
MrCraigBerry said:
So 17-55 over 24-105?
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It depends. You cold get f/4 IS, and then add a few lovely primes. No zoom can take photos like 85mm f/1.8 (or 1.2) wide open, 50mm f/1.4 and so on.
 
With modern bodies being able to reach silly high ISOs with more than acceptable results, the argument about using f/2.8 over f/4 isnt as valid, although it's still a major consideration when thinking about AF and viewfinder brightness. Of course, DoF is more flexible with the wider lens also, which is a given.

However, you're on a 40D, which was never renowned for being amazing at high ISO, so I'd probably opt for a fast lens instead of relying on the sensor to make up the shortfall in available light. Plus, the majority of 17-50/55mm f/2.8 lenses are top-notch and you'll be impressed by the image quality you get from them. Tamron, Sigma, Tokina plus Canon all make variants tht cover that range, all at varying prices. The Canon is supposed to be very good, but the Tamron I use is very good also for half the price.

Plus, 17-XXmm is a much easier option to use every day on a crop body over a 24-105, which although it has the range, is an awkward wide end for crop body use.

Now, a 17-105mm f/2.8 would be handy. but I don't think we'll be seeing one of those any time soon.
 
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"With modern bodies being able to reach silly high ISOs with more than acceptable results, the argument about using f/2.8 over f/4 isnt as valid,"

There must still be a speed advantage for some users and then there's the biggie of DoF that's really the biggie for some people.

Personally I don't think I'd ever consider an f4 lens if there was a faster alternative unless there was some other big deciding factor and I'm struggling to think of one.
 
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