Super Wide Angle Prime lens questions

[jeff_kao1]

I am new to photography & am using a EOS Digital Rebel XTi that I bought

earlier this year. The lens I use the most is a Tamron SP AF11-18mm F/4.5-5.6

zoom lens. I mostly find myself at 11mm and would like to find a faster prime

lens to replace my zoom.

 

So far I have been looking at following super wide angle prime lenses:

Canon EF 20mm f2.8 USM ($461.95)

Canon EF 15mm f2.8 Fisheye ($637.95)

 

-Will either of these lenses be "better" than my Tamron zoom?

-How is the 15mm Fisheye different than the 11mm I've been using? What makes a

lens Fisheye?

-Are there any other lenses I should be looking at? When I used the search I

saw someone is '04 recommending a Sigma lens I can't find.

[bryantan]

Are you at 11mm because you need more speed or wider angles? Both will be a stop and a third faster but both will be significantly less wide than 11mm.

 

A fisheye lense is a lens that is not rectilinear.

 

I think Sigma just announced a 10mm 2.8 lens, and I think that might be your best option for a super-wide prime on a crop.

[sdsalyer]

I'm not sure there's a wider rectilinear lens than the 10-22mm (and comparable) zooms for APS-C cameras. The widest EOS prime lens is the 14mm 2.8L (I think), which would be like 22mm on your crop camera. It is faster, but you won't have as wide a field of view.

<p />

Fisheye lenses distort the image (e.g. a straight line might become a curve), whereas rectilinear lenses try to keep things nice and straight and square (though that's often not the case). Fisheyes are really a specialized sort of lens, some don't even project a square image onto the frame, any many can do 180 degree field of view in one or more directions. You can read more about it <a href="http://www.bobatkins.com/photography/technical/field_of_view.html">here</a>

[jeff_kao1]

I tend to be at 11mm 'cause I like the angles, but in general I find my photos look dark when compared to my 50mm f1.4 lens. After reading what rectilinear means just now (Thanks!) I realize that I do not want a fisheye lens since while I like the wide angles I do not want everything to look so crazy.

 

Do you know where I can find more info on the Sigma lens?

[asher]

I've used the Canon EF 20mm f2.8 USM on an APS-C body in the past,. It's an older design,

big, heavy lens for a prime, with fairly decent optics (based solely on my subjective personal

experience). It could be worth it on a full-frame body where you maximally exploit the focal

length, but on a digital Rebel it might feel like overkill just to get a 32mm field of view.

[bongeiste]

I'm not sure this is the same lens mentioned earlier, but, if it is, it's probably not what you want, because it's also a fisheye.

 

http://www.the-digital-picture.com/Press-Release/Sigma-10mm-F-2.8-EX-DC-Fisheye-HSM-Lens-Press-Release.aspx

[zigzag]

I don't think you'll be able to get much wider than what you already have. <a href="http://www.photozone.de/8Reviews/index.html">Here</a> are reviews of most of the lenses available for Canon. I think the next widest option for you is the Canon 10-22mm (marginally wider than the Sigma 10-20mm) - there is an 8mm Fisheye there too.

 

If you are finding your photos too dark then you probably need to think more about the shutter speeds, aperture and ISO you use more than about buying a new lens. If you are not already familiar, read about 'Ev' compensation and maybe push it up a stop. You can always lighten pictures in post processing - it's having sufficient shutter speed that makes you need faster lenses - is this a problem?

[jeff_kao1]

No, I'm not having any problems that I am not already fixing afterwards in Photoshop. More I was asking about what else is around since I am very new to the field. Thanks for all the responses I definitely have a lot more reading to do.

[zigzag]

This one is a good place to start reading: <a href="http://photonotes.org/articles/beginner-faq/">FAQ</a>

[gdanmitchell]

<p>Glen, kind of a broad suggestion, no? ;-)

 

<p>This gets a bit closer:, though there are still a lot of sub links to go through. <a

href="http://photonotes.org/articles/beginner-

faq/lenses.html">http://photonotes.org/articles/beginner-faq/lenses.html</a>

 

<p>I'm not sure that this will help a whole lot in terms of answering your <i>specific</i>

questions.

 

<p>Another good thing to do is read some of the lens report web sites like photodo.de

and slrgear.com, where they often summarize the features and quality of various lenses.

[zigzag]

Jeff, do you see your requirement as wanting more Field of View (FOV)? Read this: <a href="http://www.bobatkins.com/photography/technical/field_of_view.html">FOV</a>. First thing to note is that on your Xti the 11mm lens is effectively a 17.6mm lens and a 10mm lens acts like a 16mm lens. Plug those numbers into the calculator in the link to see how much wider you could expect to see with a 10mm rather than a 11mm lens. Note also, as stated in the article, you can transform Fisheye images in Photoshop to get near to the rectilinear image, with some loss.

[sattler123]

Please don't take this as an offense, but as you said you are new to photography and many newcomers tend to use the widest lens they have in the beginning, because they like the look of it, but they grow out of it very fast. It gets old real fast and you will want to capture more detail and more of the essence of a scene. I would stick with what you have for a while - I am sure your style will change. If it does not, then in 6-12 months you will have a better understanding of all the lenses out there and what the difference is between a fisheye and a regular lens to make an informed decision.

[alan_myers]

Hi Jeff,

 

The new Sigma 10/2.8 lens is also a fisheye lens, so from your earlier response, not what you are looking for.

 

10-to-whatever zooms are the widest currently available lenses for most cameras. There are no primes with this wide field of view. (There are some 7mm and so forth, but those are for smaller format sensors like the Olympus FourThirds, and thus aren't significantly wider in the end.)

 

In other words, you could buy a 1mm wider lens than your current one. Not that 1mm doesn't make a difference. It is noticeable at ultra wide angle fields of view.

 

Also, there is some variance between what's marked on lenses and what they are in reality. This is because the focal length may be rounded to the closest full mm, or for other reasons. Essentially, 10% is allowable under testing standards, so a lens marked "11mm" might actually be 10mm or 12mm in reality. If you were to line up 4 zooms from different manufacturers all marked "11mm" at the widest setting, it's entirely possible you could see a small difference between them.

 

So, you really have to compare lenses side by side, to make a final judgment.

 

You mention that your primary issue is that the images produced by the zoom are too dark, compared to your 50/1.4. Exposure isn't really a factor of anything we've been discussing here. It doesn't really mean you need a faster lens or a wider one, or even a prime. It sounds more like you are having problems with exposure.

 

You may already know, you can increase your camera's ISO or use a slower shutter speed, if you are using the lens wide open (i.e., at it's largest possible aperture setting... f4.5 in your case) and still getting a dark image. The camera should be warning you of underexposure. If not, then there may be a problem of communication between the lens and the camera. It might be a matter of adjustment, or just a nuance of the particular lens or lens/camera combo.

 

You will rarely see ultra wide lenses that have f2.8 aperture, and almost none larger than that. This is for three reasons.

 

One is that an ultra large aperture is sort of meaningless for background blur, which is one of it's key uses on normal and telephoto lenses. The wider the FOV of a lens, the less background blur it produces and the deeper its depth of field. So, most wide angle photography emphasizes the opposite, depth of field coverage from near to far, and most users are stopping the lens down, not using it wide open.

 

The other reason is that super and ultra wide lenses introduce a lot of optical aberrations at large apertures. This is sometimes "coma", other times chromatic separations. Optically speaking, it's very difficult to design and build a really good ultra wide with a big maximum aperture. Exotic glass and shapes for elements have advanced wide angle optics a lot in the past ten or fifteen years, but there are limits.

 

Third, there is less need for large apertures on super and ultra wide lenses because they are more easily hand held at lower shutter speeds. The old rule of thumb said that most people could safely handhold a lens at 1/focal length. So, you might expect to need 1/50 with a 50mm lens, 1/11 with an 11mm lens. The "crop factor" of modern D-SLRs has an effect, though, in essence magnifying any camera shake along with everything else. So, if an 11mm lens "acts like" a 17mm on your camera, you'd want to set a shutter speed faster than 1/17 to be safe (round up to the closest, faster shutter speed, of course).

 

Still, in comparison to, say, an 85mm lens that requires 1/136 or faster shutter speed to be safely hand held on the same camera, there's just a lot less need for very wide lenses to have a super fast aperture.

 

Finally, if an even wider angle of view is also - or actually - what you want, have you looked into stitching photos together? This starts with a series of shots, often best done with a more normal lens that will introduce wide angle less distortion that can cause problems later.