The lens is too 'slow' or too 'fast'

[max_rockman]

Sorry for flooding the board with 'newbie' questions, but thank you to all who

have responded with detailed and comprehensive answers!

 

What do people mean when they say things like "personally I find the 17-85mm

f4-5.6 lens too slow"

 

thanks.

 

 

max

[tommyinca]

Slower means when set to the lens max aperture, the shutter speed is slower.

 

e.g.:

 

a. f5.6 at 85mm is consider as slow when compared to a 85mm f1.8 prime (single focal length) lens. It is 3 & 1/3 stops (times) slower.

 

b. Compared to a 24-70 f2.8 zoom, it is 1 to 2 stops slower.

[max_rockman]

Also, of the two different kit lenses offered with the Canon 30D, which is recommended more? The 17-85mm or the 18-55mm?

[jwhite3.0]

A max aperture range between f/4-5.6 is "too slow" depending on what you need to do. If you're doing action photography a larger aperture (say f/2.8) will allow you to "better freeze" movements rather than have a blurred image. You can get around this a little by increasing ISO speeds and reducing exposure time but that may come at a price in terms of image quality. Just think of it in terms of the amount of light able to reach and expose your film or sensor. With all things being equal, fast or large aperture means more light which in turn results in getting that film or sensor exposed quickly.

 

If you're using your lens for say landscape during times of good light and with a tripod then for you it may not be too slow. Good "fast lenses" come at a price, higher aperture means more high-quality glass which means less in your bank account.

[gdanmitchell]

Most people would probably think the 17-85 is "better," but it also comes at a higher price.

[max_rockman]

Thanks for the help so far. I'm now thinking of buying the 20D instead of the 30D and using the extra cash to purchase a faster lens, anyone think I'll regret choosing the 20D over the 30D in the future?

[jwhite3.0]

As for kit lenses, buy what you can comfortably afford. Sounds like you are just starting out and figuring out what this whole hype is about in terms of lenses. If anything, get the body only and buy a Canon 50mm f/1.8 lens. Play with that a little while then buy the best glass you can afford while taking advantage of the Canon double rebate. If I am wrongly assuming your level of expertise then sorry about that. Let us know what type of photography you are most interested in because we can make a lens suggestion and you will not have wasted money on a kit lens that isn't suited to your needs.

[max_rockman]

I've shot BW film for 6 or 7 years but used the same F100/50mm setup and never took the time to essentially learn photo 1 so the terms are all new to me but I understand what they mean.

 

I'll be using the camera for say 50% candid photography (friends, parties) 35% fashion photography, and 15% sports photography... roughly.

[tim_kong]

If you are a ''newbie'' to photography, there won't be much difference between the 2 cam. In fact the 2 cams are pretty much the same except a bigger LCD for the 30D. Apart from that, I don't think you will miss the other extra features from the 30D. The 20D has more than enough features to last you a long time. Its better you spend the money saved from getting the 20D on a good lens to start with. Good quality lens will give you better image quity than newer model. camera

[jwhite3.0]

Sounds like you may want a "fast" or large aperture lens that will allow you to have shallow depth of field for those candid shots of family/friends and for that 15% of the time use for action photography. One of the best zooms on the business that might allow you to accomodate many of your needs in one lens is the Canon 70-200mm f/2.8 lens (~$1100). Other less expensive options include some fast primes such as the 85mm f/1.8, 135mm f/2, or 200mm f/2.8.

[max_rockman]

I've been reading some online comparisons and have decided to definitely go with the Canon 20D. Something I need to keep in mind for my primary lens is that I need to be able to fit the camera into my bag so the lens can't be too big. Also, carrying around a large lens at a party is a hassle.

 

I'd really like to get that 17-55mm f2.8 lens, i think... But for now it's out of my range. The 20D body is roughly $1,000. I have 700 tops left to spend on a lens for it.

[david_french3]

It's totally subjective, but I've found I've ended up spending at least as much on each lens as I

have on the body, in order to get optics which do justice to it.

[alan_myers]

Hi Max,

 

"Fast" and "slow" is just as other responses have said, refers to the relative, maximum aperture size of the lens (which often varies as in a zoom lens example such as the 17-85/f4-5.6).

 

A fast lens is one that has a very large aperture and allows shooting in lower light, such as the new 50/1.2L Canon just announced. A lens that has f4.0 as a starting point is "slow". But, everything is relative. In large format, an f8.0 lens isn't uncommon and f5.6 is fast. In medium format, an f2.8 is quite fast. A fast zoom for 35mm/D-SLR is f2.8, but in a prime lens this is only moderately fast.

 

Yes, in addition to the advantages when shooting in low light, a larger apertured lens will allow a softer background, nice for portraits. In fact, most D-SLRs put a little more demand on lenses in this respect, an f2.8 lens on a full frame will render a softer background than it will on a 1.6X sensor crop camera. On the 1.6X, an f2.0 might be roughly equal in that respect.

 

Also, larger aperture lenses make for a brighter viewfinder and, due to their more shallow depth of field when wide open, can make for more accurate manual focusing.

 

Auto focus is also effected by a lens' speed. Generally speaking, larger aperture lenses offer faster and more accurate auto focus. This because the sensors have an easier time with the target. And, some AF systems are ineffective at slower (smaller) apertures . In fact, f5.6 is the point where many cameras AF starts to get slow or lose capability, and most lose AF completely at f8 or smaller apertures.

 

So, if for example you spend your hard earned money on a lens that is f5.6 at the longer end of a zoom range, and have plans to use that lens with a 2X teleconverter, you might be pretty disappointed. With the teleconverter installed, the maximum aperture is two stops less, or f11. Not only won't the AF system work, but the viewfinder is pretty dim to try to manually focus.

 

On the other hand, aperture is a ratio of the size of the opening within the lens in comparison to the focal length of the lens. So, to be an f2.8 lens, a 300mm needs to be quite large in diameter (to allow for 107mm diameter aperture!). This adds a lot to that lens' difficulty to manufacture, weight, overall bulk and cost.

 

On the other hand, there are times when "fast" might not be the best choice. Often, particularly among wide angles, very large aperture lenses are not the most critically sharp. In the case of a 17mm lens, for example, f3.5 or f4 might be closer to optimal. This is keeping in mind that most shooting with wide angle is looking for just the opposite of a portrait lens, sometimes extreme depth of field from foreground to infinity, all in reasonably sharp focus. Also, presumably, a shorter focal length is more hand-holdable at slower shutter speed, so is more tolerant of a slower lens.

 

In the end, any lens is a compromise of speed, optical design and manufacture, sharpness, color rendition, correction of aberrations, size, weight, complexity, durability, cost, ergonomics and more. There really is no such thing as a perfect lens. But, you generally get what you pay for, and IMHO, lenses are not the place to skimp with any camera system.

 

Cheers!

[yakim_peled1]

http://photonotes.org/articles/beginner-faq/lenses.html#slowfast

 

Happy shooting,

Yakim.

[mark u]

Fast lenses also allow a distracting background to be thrown more out of focus, making the subject pop from the scene. With 1.6 crop sensors, you need a faster lens than you would do with full frame to achieve the same degree of background blur.

[hash]

>> With 1.6 crop sensors, you need a faster lens than you would do with full frame to achieve the same degree of background blur.

 

This needs to be explained a bit more. A 50mm 1.8 lens will create the same image and same background blur regardless of the crop factor.

 

But to get the same picture with a cropped sensor, we would use a 30mm lens, which has less background blur at the same aperture. So to get the same blur as a 50/1.8 on full frame, one might have to use a 30/1.4 lens on a cropped sensor.

[yakim_peled1]

http://www.photo.net/learn/optics/dofdigital/index.html

 

Happy shooting,

Yakim.

[byronlawrence]

this is nit-picky on my part but "It is 3 & 1/3 stops (times) slower." this statement is just slightly off.. 3 & 1/3 stops is actually closer to 10-11 times faster (each stop is twice as much/half as much as one stop more or less)

[m_barbu1]

<p><i>Thanks for the help so far. I'm now thinking of buying the 20D instead of the 30D and using the extra cash to purchase a faster lens, anyone think I'll regret choosing the 20D over the 30D in the future?</i></p>Possibly, but I think you'll regret getting a slower lens more than you would regret getting a "less featured" body. It doesn't matter how many features your camera body has, if you can't take the shot, because you don't have enough light.

[delwyn_ching]

When a lens is rated as "slow" or "fast", people are referring to the aperture opening or f-stop (in the olden non-digital days as is was called and still called by many today). A slow lens would have a f-stop of say f/8, f/22, etc. When compared to a f/1.2, f/2.8, or f/4 which are considered faster than the f/5.6 or f/22. It's all relevant and depends which lens you have. Your sample lens is the 17-85 f/4-5.6 which is "slow" when compared to a f/2.8 but "fast" when compared to one that is f/6.3! Get yourself a good beginner's book such as "Understanding Exposure" by Petersen or other beginners books. Good Luck

[William Michael]

Whatever you decide, re read and note well what Mr Barbu said.

 

I think you'll regret getting a slower lens more than you would regret getting a "less featured" body.

 

It doesn't matter how many features your camera body has, if you can't take the shot, because you don't have enough light.

 

I completely agree: over 32 years I have never regretted paying out for a quality faster lens - all other issues being equal - in good hands a quality fast lens will give you quality results on a body even less costly than a 20D but as poorer lens will limit you tremendously on even a $50,000 body.

 

A lateral thought: you might consider prime lenses; you will be forced to learn much, more quickly.

 

Also take up the suggestions regarding good basic texts - buy one or two and read them cover to cover and then read them again.

 

M. J. Langford was standard text in Australia for 1st year students for years.

 

BASIC PHOTOGRAPHY would be a good start; he explains the technical in easy to understand and applied terms - see if you can dig up his books.

 

My next comment is with great respect to the combined knowledge and experience represented at this site and other www photography forums and information sites, (from which I have taken and absorbed much, thank you): the information on line is what it is, and a tried and tested text book is what it is, also.

 

Regards WW