F2.8 Through Zoom Range

Captured Exposure

Hiya,

I finally have now upgraded and gotten a new lens Tokina 11-16 F2.8. It has the F2.8 through its whole range.

One thing I don't quite understand is, if it is F2.8 through the range, do you get clear shots for landscape @ f2.8 or do you still need to stop to something like f8. The lens also has an infinity setting so does this overcome the f28?

Hope that makes sense...

Thanks

Scott_Quier

Take a look at DOF Master. Enter f/2.8, focal distance of 8 ft, and focal length of 11mm for a Canon cropper and you will get DOF range from 3.8' to infinity. At 11mm on a cropper, your hyperfocal distance is approx 7.5 feet, which get you everything from 3.75' to infinity "in focus".

Of course the numbers will change with changes in both focal distance and focal length. Playing with that DOF calculator should result in a better intuitive understanding of the relationships involved.

The infinity setting refers to the focal distance - when the lens is set in this manner, the focal distance of the lens is such that it will sharply resolve objects at that distance. Refer back to the DOF calculator for a better understanding of what is going on here.

zoomer

To begin with you will want to test your lens to see if has the potential of sharpness at f2.8 at any distance, it will probably need to be at least at f4 before it starts to get sharp.

As mentioned check the depth of field chart.
Typically unless you have a photo element very close f8 to f11 works great for landscapes.
If you have something very close f-16 should work, if you go higher than that you will start to lose sharpness and unless something is right at your feet you should not need to go higher.

cab.in.boston

Scott, thanks for pointing this out. I have used DOF Master before, but not to look at hyperfocal distance on UWA zooms. So this makes me curious...

Since at these short focal lengths, the hyperfocal distance tends to be very close, is there really a compelling reason for a constant aperture UWA zoom?

I have heard that the Nikkor 14-24 f/2.8 is one of the best WA zooms ever, but it seems if you're using it (or any other WA zoom, really) for anything other than very close in work, then your DOF is either going to be infinite or might-as-well-be infinite.*** At 14mm/2.8, hyperfocal distance is 11.4'. I understand this isn't the preferred portrait/subject isolation type focal range, but it just makes me wonder if it's really worthwhile to spend the extra money for the aforementioned Tokina ($600 @ B&H) or Sigma 10-20 f/3.5 ($649) vs. the variable aperture Sigma 10-20 ($479).

So yeah, it boils down to, what's really the reason for a constant aperture UWA zoom?


*** Disclaimer: I totally understand there are other reasons to buy a WA zoom like the Nikkor 14-24 than just DOF, I'm not trying to suggest that one would pass on that lens for that reason alone.

zoomer

f2.8 to probably around f36 would be the range of f-stops available.

Not sure if I understood your question.....

cab.in.boston

zoomer wrote:

Not sure if I understood your question.....

Assuming this is meant for me, I'm simply unclear on why having a constant 2.8 (or 3.5, in Sigma's case) is really important for an UWA zoom. Since many people are likely to be using them stopped down for land/cityscapes (that will be my main use once I get one), and the hyperfocal distance is so close anyway, what does the f/2.8 really get you that f/4 or f/5.6 doesn't?

Obviously more light is more light, and that can't be bad. But it just doesn't strike me as nearly as important to have a large aperture for UWA than it does for a 70-200 or 24-70/17-50. So why, as an amateur, does it make it worthwhile to me to spend the extra money for the constant f/3.5 of the Sigma or f/2.8 of the Tokina? I just don't understand the usage in which it would make a big (or any) difference.

zoomer

Can't argue with that.
Wedding photographers sometimes like a very short depth of field, so there would be some application there for 2.8 (if it were sharp at 2.8), but yeah for landscapes not so much.

D'Buggs

I think that a lens such as the one the OP mentioned, would be more of a 'creative' lens when used @ f2.8

Think of all the possibilities of distorted close-ups that have great seperation.... Having options and versatility, seldom hurts.

cab.in.boston

zoomer wrote:

Wedding photographers sometimes like a very short depth of field, so there would be some application there for 2.8 (if it were sharp at 2.8), but yeah for landscapes not so much.

That was kind of my point bringing up the Nikkor 14-24. That is supposedly an outstanding lens that many pro wedding photogs might have. Thom Hogan says it's so good that it beats all 4 of the Nikkor primes in its range (14, 18, 20, 24), and is incredibly sharp. By all accounts, this is a lens worth owning, indeed I've heard rumors of Canon shooters using this lens with some kind of adapter.

So let's say you're using it at 14mm, f/2.8, and at the MFD (0.9 ft.) - your DOF is 0.14 ft. Nice, could probably get some interesting detail shots shooting that close. But your hyperfocal distance is only 11.4 ft, so get to anywhere near a "comfortable" working distance shooting people, and your DOF starts getting deep pretty fast (21.9 ft when working at 8 ft).

Obviously, at the tele end of this lens, you have thinner DOF and a higher hyperfocal distance.

I'm probably just rambling, and I have a friend who loves his Tokina 11-16 f/2.8, but he is often saying how it's so much better than its competition b/c of the constant 2.8. Personally, I think the difference in angle of view that the 10mm of the Sigma (better yet, the upcoming 8mm) gives you is worth more than the aperture, at this focal length. 11mm on DX gives you 94 degrees horizontally, while 10mm gives you 99.4 (8mm = 111.7).

I'm just interested in more experienced photogs' opinions on why the constant 2.8 is really so important for UWAs. Like I said, I totally understand the need/use for fast glass for longer lenses, I'm just intrigued by whether or not it really makes a huge difference down in the 10-15mm or so range.

colourbox

cab.in.boston wrote:

So yeah, it boils down to, what's really the reason for a constant aperture UWA zoom?

I have a Canon 17-55 constant f/2.8. One reason I bought it was because I did want to be able to reduce the depth of field with close range wide angle portraits. But the bigger reason for me was not related to depth of field, hyperfocal distance or any of that.

It was largely so I could get more pictures in low light.

My previous zoom was a f/3.5-5.6, which means getting low light shots was challenging at 17mm (f3.5) and ridiculous at 85mm (f/5.6). With the constant 2.8, I know that I'm always getting as much light as possible into the lens regardless of focal length. This means I can use slower, less noisy ISO speeds...maybe 400 instead of 800 or 1600. Or...having the fast aperture always available, you might gain the flexibility of using higher shutter speeds to stop action. There is just no contest between shooting in low light at f/2.8 vs f/5.6.

A fast constant-aperture wide-angle zoom is pretty much the ideal lens for indoor available-light shooting. Wide angle is good because you can't back up too far when in a small room, and you have the widest aperture always available to you for maximum light gathering in case you can't/don't want to use flash.

Qarik

yes the 2.8 aperture on an UWA is not as critical for landscape shots where often your subject matter is farther away. The 14-24mm is incredible not only becausee of center sharpness at 2.8 but corner to corner sharpness is almost perfect wide open and better then other WA that are stepped down. Also it is nearly distortion free and almost zero vignetting and zero fringing. It also better built and fits on full frame.

Captured Exposure

Thanks all, appreciate the advice. Is clearer now, for some reason I thought f2.8 meant it was all in focus for the lens range at that aperture.

I will have a bit of a play with DOF master as well.

cab.in.boston

colourbox wrote:

I have a Canon 17-55 constant f/2.8...

I totally agree with everything you said, for this focal length range. I have a Tamron 17-50 f/2.8 (I shoot a Nikon D90 - 1.5x crop) and I love it.

I'm talking more about the Ultra-WA range, like the OP's Tokina 11-16mm, or Sigma 10-20 (or their newly announced 8-16), Nikkor 10-24, etc...