Fast lenses are more expensive to manufacture. they need more optical elements to correct distortion (and these means more mechanical parts as well); larger maximum aperture, with larger pieces of glass, means the light needs to be bent more acutely and hence requires more correction. Often this means using more expensive high refractive index glass, low dispersion glass and / or aspherical lens elements and more expensive anti-reflection coatings to cut losses at the air / glass interfaces.
Is there better image quality? Not necessarily; faster lenses may in fact perform a bit less well that slower ones, but that issue tends to go away after one stops down two or three stops from wide open. If you look at the lens reviews of the f/1.2 or f/1.4 lenses 50mm fixed lenses; performance can be a bit worse that the relatively inexpensive f/1.8 ones; but of course your tradeoff is better low light performance as well as shallower depth of field. These tradeoff might very well be worth it, depending on the type of photography you are planning to do.
To me, I often shoot wide open to get the very narrow depth of field or to let me shoot at a lower ISO (better colour depth and less noise), so I use "fast glass". If these characteristics are less important to you, you could save yourself a fair bit of money (and weight) by going to slightly slower lenses. It's all about which tradeoffs are most important to you.
Also, the need for a very fast APERTURE to arrest Subject Motion has become less over the past few years with the advances in very good, very high ISO performance of digital cameras.
For example, in 2002~4 it was absolutely imperative for me to be able to use F/2.8 with a 300mm Lens to shoot Competition Swimming Events from the poolside, because with an EOS 1D used at ISO1600, we needed F/2.8 to get the appropriate Shutter Speed (flash is prohibited); but today, a recent release APS-C camera with the kit 55 to 250 lens can make the same necessary Shutter Speeds using that kit lens at its minimum Aperture of F/5.6, simply by bumping the ISO to ISO 6400.
Sure, the Kit Lens might not have the same optical quality and the resultant shot will not have the same Shallow Depth of Field as I would have using an EF 300 F/2.8 L, but the point is, the very fast Apertures that we required to arrest Subject Motion are not as necessary now that sensor performance has improved at the high ISO levels: the take home is with a reasonable amount of skill, knowledge and experience, a Mum or Dad can indeed often get reasonably good, sharp shots of their kids at a night-time Football; Indoor B.Ball; Gymnastics; Swimming etc, with a recent release APS-C DSLR Camera and the pair of Kit Lenses.
WW
I think that it is good that you want to experiment with different approaches to Portraiture. It stifles creativity to adapt the approach that any one particular lens is dedicated to any one particular Genre of Photography. Portraits can be made with many different Lenses, as can Landscapes.
Below is selection of Portraits all of which are made with an EOS 5D, using Available Light and the various different Lenses, as mentioned below each image:
15 F/2.8 Fisheye
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16~35 F/2.8
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24 F/1.4
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35 F/1.4
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50 F/1.4
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85 F/1.8
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100 F/2.8 Macro
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24~105 F/4
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135 F/2
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70 to 200 F/2.8
WW
All Images ŠAJ Group Pty Ltd Aust 1996~2015, WMW 1965~1996
A wide angle lens can be quite effective in environmental portraiture by including the environment around your subject...
However, for traditional portraiture, I prefer longer focal lengths because of the lack of distortion when shooting from a distance. I think that longer focal lengths are more flattering, especially for female subjects. I looked at many of my portraits and most of them are shot with 100 mm or longer focal lengths on a 1.6x crop camera (160 mm equivalent). OTOH quite a few of my portraits have been shot at 200 mm (320 mm equivalent, such as this portrait...
I use small apertures on good lenses for depth of field. I know there is some loss of sharpness, so far this has not bothered me as a problem. I would have to check, but I suspect most of my stuff is shot at f16 or smaller
70-200mm f2.8 at f22
Micro Nikkor 200mm f4 at f29
16-35 mm f4 at f18
70-200mm f2.8 at f22
50 mm f1.8 at f16
Last edited by tbob; 2nd June 2015 at 02:31 PM.
A couple people have mentioned the lack of sharpness when shooting at a very small aperture. The CiC tutorial explaining diffraction puts the concern in context by explaining the following: "Even when a camera system is near or just past its diffraction limit, other factors such as focus accuracy, motion blur and imperfect lenses are likely to be more significant. Diffraction therefore limits total sharpness only when using a sturdy tripod, mirror lock-up and a very high quality lens." I would add when making a relatively large print to that list.
I second Mike's point.
I am a bit obsessive about sharpness in my images as the wood grain detail in the old buildings is a crucial component. So I shoot Mirror Up on a sturdy tripod. And I print at 20 by 30 inches (50 by 75 cm). So far any loss of detail due to diffraction has been an utter non issue.
Last edited by tbob; 2nd June 2015 at 08:25 PM.
Me too.
Knowing what Shutter Speed is necessary; Using a Tripod/Monopod and Head correctly, Using MU Technique, Correct Camera Holding Technique; Correct Shutter Release Technique; understanding how the AF works; Best Practice Post Production Sharpening - should all be on many Photographer's hit list, well before their concerns about diffraction.
WW
Trevor - I love the Cloudscape. Bravo.
^^^ . . .ta Mike,
but it was you who got the fire stoked under me: one of my hobby-horses.
I actually love theory; and detail; and mathematics; and pedantry - but like them all to "add to", and not to "distract and detract from"
WW