In which situations do you really need f2.8 vs. f4?

[michael_ransburg2]

Hi all,

 

the benefits of a large aperture (e.g., f2.8) are clear: 1) Faster autofocus, 2)

Better control of DoF, 3) Better low-light performance. At f4 one might have a

slightly slower autofocus in low-light, slightly larger DoF and of course a

decreased low-light performance.

 

In practice, however, it very much depends on the situation and your shooting

style to which extend the differences between f2.8 and f4 really count. For

example, for shooting a portrait on a crop camera (I assume 50mm with the

subject 2 meters away) the DoF with f2.8 is 17cm and at f4 24cm. This is a very

small difference and probably negligible for most shooting situations.

 

One situation where I assume that f2.8 is absolutely needed (please correct me

if I'm wrong) is for sports photography at high tele-ranges (no flash possible)

in low light situations. I guess that in such situations you'd have the ISO

already at the limit even with f2.8, without any chance to compensate with flash.

 

The question I therefore have is: What are your real-life situations where you

really needed f2.8 and could not possibly have worked with f4 (Let's assume the

lenses being otherwhise identical)?

 

I'm looking forward to your inputs.

 

All the best,

Michael

[picpocket]

whenever I need one more stop. Say 1/100 sec instead of 1/50 sec

[michael_ransburg2]

Dear Ashish,

 

I explicitely asked for real-life situations (e.g., real examples) in order to avoid abstract replies.

 

Many thanks,

Michael

[will king]

Any indoor situation with no flash.

[KenPapai]

Look at it this way -- in what situations would you rather have f4 glass than the equivalent, but in 2.8?

 

Remember one of the oldest and wisest rules: AF systems love fast glass and so do your eyes when manually focussing.

 

Unless lens weight and $$$ are *primary* concerns you can never go wrong with faster glass.

[zacker]

Wedding shooters love f2.8 as most churches are dark and wont allow flash.

 

You covered sports, besides that, any type of action shots, indoor and out.

[nick_bumgardner]

Michael

 

Lenses that open up to f2.8 can be very useful in many situations over their f4 cousins. F2.8 offers much more light into the lens. This allows the af to focus faster and for you to see much better through the lens.

 

Examples. Most of my work is wildlife photography and f2.8 and f1.8 have allowed me to take many early morning light shots where f4 or f5.6 would not have cut the mustard because I was after a shot of an animal and it was moving in morning light. Fast glass can really pay off. The name of the game is getting as many good shots as you can. IF you do not have that extra stop you might loose a shot. For indoor shots f2.8 can be amazing too where you do not want a flash. If you are in a dark room with moving people and want the shot you need f2.8 or 1.8 or even f1.4 or f1.2.

 

Good luck

 

Nick

[micha__stachowski]

I would like to add that in portraiture and art photography (and in many other areas) you often want a shallow DOF. 2.8 will allow you for a bit shallower DOF then 4, also if you use manual focus it is a god-sent.

[michael_ransburg2]

Hi Michal,

 

I agree that f2.8 allows shallower DoF than f4. However, as I state in my original post, I'm not sure how much difference this makes in real world situations. Specially for portrait photography, where the subject is close to the camera, the difference in DoF is really very very small and often not relevant.

 

The "online depth of field calculator" will let you verify this:

http://www.dofmaster.com/dofjs.html

 

Don't get me wrong. There are certainly situations where this little bit of difference really makes a difference in the photos which you get. I'm very curious to learn about these specific situations.

 

All the best,

Michael

[guido_ersettigh__milan_]

excluding when I shoot with wideangle, I always prefer large aperture lenses, first of all for the better DOF control, then for shooting at higher speed. I've almost always preferred prime lenses than zooms expecially for their aperture - 1.4, 2 ... - , so 2.8 would be just acceptable to me. I don't even take in account f4 lenses for focals inside 200mm thou the new 70-200 f4 IS is so good I honestly thought to buy it... but I finally decided I'll go for the 2.8 version. Consider that a lens you use for shooting sport images needs to be fast: IS doesn't helps with moving subjects and cannot trade the DOF control you have with a faster lens.

[michael_ransburg2]

Hi all,

 

many thanks for your inputs so far, which helped to identify two situations where f2.8 is a necessity and f4 is not sufficient:

 

- Outdoor photography at high tele-ranges (no flash possible) in low light situations (e.g., sports, animals)

 

- Any indoor low light situation where no flash is possible (e.g., wedding)

 

I'm looking forward to learn about more specific shooting situations where f2.8 is absolutely necessary.

 

Many thanks,

Michael

[rob - atlanta, ga usa]

F/2.8 is also better when you plan to use a teleconverter. With an f/4 lens and a 1.4x converter, the lens' effective aperture becomes f/5.6. With an f/2.8 lens and a 1.4x converter, the effective aperture becomes f/4.

[matt_needham]

Lenses tend to be sharper with the aperture closed down a stop or a few compared to wide open. Even if I do only need f/4, I'd rather be shooting at f/4 with a f/2.8 lens than a f/4 lens.

[denisbergeron]

Ever take a portrait with f4 lens ! <i>Which <b>Beurk</i></b> !<br> Use a f1.2 lens. <br> Voilà un vrai portrait.

[lester_wareham]

The main advantages in the f2.8 is multiple:

 

a) more light is reaching the AF sensor so AF will be more positive with less chance of hunting in low light situations. Others may disagree with me but my experience is that in good light the AF speed is the same for f2.8 and f4 lenses.

 

b) again with the AF function, the AF will be more consistent, ie will have a smaller spread because the camera has higher accuracy sensors that can only work with f2.8 lenses. However from tests I have done, we are talking very small variations that will be difficult to detect even at 100% crops without software, so in the real world I don't think this is that big a deal.

 

c) Most obviously f2.8 is a stop faster than f4 permitting a faster shutter speed, but (and this is important) with smaller depth of field. This allows you to handhold and freeze subject movement in lower light levels.

 

d) As noted by Bob you can use a 2X TC on a non-pro body and retain AF, where as with an f4 only a 1.4X.

 

e) You can use smaller depth of field to isolate the subject for artistic reasons.

 

Now with the f4 lens, if for example it has IS compared to a f2.8 lens without IS the f4 lens can probably be handheld in a stop or two lower light levels than the faster f2.8. However, the shutter speed is still low so you can not freeze subject movement. On the other hand you can handhold and still be a 2-3 stops better off for depth of field.

 

So which lens is best in low light depends on the subject and if it is moving significantly.

 

For a moving subject that is not too deep like a human being a f2.8 lens is probably best in low light even if it does not have IS.

 

However, for a non-moving subject with significant depth the the f4 with IS lens may be best in low light assuming you have to handhold and can't use a tripod.

 

Finally, if you use that non-IS f2.8 lens with a monopod you will gain about 2 stops of handholding light level.

 

Use the Monopod with an IS lens you gain 1-2 stops more over the IS depending on the focal length.

[lester_wareham]

BTW if you really want fast glass forget zooms and get primes.

[jsscheeler]

Michael,

 

You mention one application that you assume F2.8 is a requirement is in sports photography. In my experience, I can definitely agree with that. In particular I find that ice hockey demands the fastest lens you can afford. In most amateur rinks, the lighting is terrible, flash is not always allowed and the speed of the action requires high shutter speeds.

 

I currently shoot RAW with the 200mm F2.8 lens at ISO1600 and am thinking about adding the F2.0 135 lens.

 

BTW, I have tried shooting with a f4.0 lens and experienced significantly less "keepers" than when I shoot with my F2.8.

 

-Scott

[mendel_leisk]

I haven't read the whole thread, but I don't think it's been mentioned:

 

All things being equal, you will likely get better image quality shooting with an f2.8 lens stopped down to f4, vs an f4 lens wide open. Depends on the lens, but the odds of better IQ are stacked towards the stopped down f2.8.

[tapani]

One more: wildlife photography in the dark with flash. The wider aperture you have, the farther the flash reaches. (I was shooting bats the other night... wish I'd had f/1.8 instead of f/2.8.)

[michael_ransburg2]

Hi Lester, all,

 

many thanks. I do know all the theory, what I'm missing is experience, which is why I'm asking for practical usage examples. More specifically, I've been struggling for weeks now with a lens upgrade for my 400D. I've been shooting for a long time now with my Sigma 18-50 f2.8 / Canon 70-300 f4-5.6 IS combination. In my free time I'm working as a photographer for a local news site shooting all kinds of social events.

 

Based on my shooting habits (and analysis of my EXIF data) the reach of my 18-50 is not enough for me. I find myself very often shooting at 50mm, while I rarely use the wide end of this lens. Additionally, I often don't have time to switch to the 70-300 during a social event, which makes me losing shots.

 

This is why I'm eying the 24-105 f4 L lens. However, it's a very hard decision for me since I have a very hard time to let lose of f2.8. I'm not sure if I really need it or if I would do as well with f4 - this is one of the reasons for this thread.

 

One of the third party 24-70 f2.8 would be an alternative. The Canon 24-70 f2.8 L is surely superior, but I won't pay the extra price for just a little better IQ (I don't care about robustness / wheather shielding, ...).

 

I'd love the reach of the 24-105, but I'm not sure if the f4 won't limit me too much. On the other hand the 24-70 only has 20 mm more reach than my 18-50, so I'm not sure if I won't feel constrained again?

 

So it's basically 24-70 f2.8 (3rd party) vs. 24-105 f4 (Canon) for me. I say "basically" because I've also been eying the 17-55 f2.8 (Canon), but that would only give me 5mm more reach than my current lens and as I said I rarely use the wide end even on my 18-50mm.

 

As I said. I've been struggling with that for weeks and there is not shop which lets you rent lenses over here. So I'm really stuck :-(

 

All the best,

Michael

[fmueller]

"For example, for shooting a portrait on a crop camera (I assume 50mm with the subject 2 meters away) the DoF with f2.8 is 17cm and at f4 24cm. This is a very small difference and probably negligible for most shooting situations."

 

That calculation might be correct, but you are not looking at the whole picture. More important than how much is in sharp focus is how much the out of focus areas are blurred. That of course can't really be quantified, but from looking at pictures I get a strong feeling that often at f2.8 the background is significantly more blurred than it would have been at f4, which leads to a greater separation between subject and background, and can give a picture a lot more 'snap'.

[gdanmitchell]

Between the 24-70 and the 24-105 you have the good fortune to select between two excellent lenses with differing features and strengths. There is

not an absolute answer to the general question of "which is best" - you'll have to look at both, look at your photography, and determine which is the

best fit.

 

If you need f/2.8 for narrower DOF, one extra stop in low light situations at the fastest shutter speed you can use, can cover the 70-102 range in

another way, don't mind the additional size/weight compared to the 24-105, don't need to shoot relatively static shots in low light where IS can make

a 2+ stop difference - the 24-70 may be your lens.

 

If you find that f4 is narrow enough DOF for you, you often shoot at smaller apertures, shoot handheld in situations where camera shake is an issue,

want a bit more range from the lens, and are better off with something slightly lighter/smaller - the 24-105 may be your lens.

 

I have no idea what the right choice is for you. I selected the 24-105 for the following reasons: Most of the time I shoot at smaller apertures in the f/8-

f/16 range on my 5D; f/4 gives me a narrow enough DOF for most of my work; I augment the f/4 zoom with a wider aperture prime when necessary; I

often shoot while backpacking/hiking so the weight/size difference is significant; I like the IS for low light hand held work; I find that I can shoot in

fairly low light (e.g. - theatrical productions) using IS, a monopod, and higher ISO.

 

Don't discount the 17-55mm f/2.8 IS lens if you are a crop body shooter. As you said, you often shoot at the 50mm max range, and this lens will cover

it and give you both IS and f/2.8. But, as you pointed out, you lose the longer reach.

 

Selecting equipment is a matter of - depending upon how you look at it - finding the best compromise of features or finding the best fit to your own

work. No one else can tell you which is the best choice - you'll be ready to buy when you get to a certain level of confidence about these issues relative

to your shooting.

[michael_ransburg2]

Hi Dan,

 

many thanks for your reply, you are completely right with your last sentence.

 

In fact I was almost at that level of confidence when the brother of my girlfriend asked me to shoot his wedding (I made perfectly clear to him that I'm not a wedding shooter, but he wanted me anyways). Anyways, before that event I was almost sure to go with the 24-105 f4. However at the wedding I almost exclusively used f2.8 to nicely seperate the couple from the background (sometimes for the artistic effect, sometimes because the background was inappropriate). What should I say, the photos turned out wonderful and the couple was very very happy.

 

No need to say that my confidence in buying the 24-105 f4 got a major hit through this event and there I'm now again struggling between f2.8 and f4 *sigh*.

 

Maybe I'll just get the 24-105 f4 in addition to my 18-50 f2.8 and see if / how I use it and how the photos turn out. I can always resell it at a good price I guess in case that it turns out that it was the wrong choice...

 

All the best,

Michael

[lee_shively]

Ever looked through an f/1.4 lens? It's a Zen-like thing to experience. Especially when using autofocus cameras with their focus screens that are optimized for AF but not actual viewing of the subject. Actually being able to see a bright image is an unbelievable advantage. Those who only use zooms with their maximum f/2.8 apertures are missing out.

 

F/2.8 is wimpy, but acceptable. F/4 blows.

[steve torelli]

Comparing zooms at f/2.8 and f/4, the differences are substantial but in the real world, not that much so. Twice as much light etc.

 

Try shooting with a fast prime and really see the difference. I completely agree with Lee's assessment, f/1.2 or f/1.4 is a whole 'nother ballgame. Once you've gone fast primes, you'll never go back. Good luck.