Hi Gene51. Good point (what about distance), I interpreted that to mean the zoom setting. But if she meant the actual distance from her shooting position then the close focusing spec for that lens is the obvious limit. Otherwise if the subject is still very small at maximum zoom then the resolving power of the sensor becomes the limiting factor. What is your assessment about her question?

I think the problem with using maximum aperture (with respect to sharpness) as a guide has to do with the depth of field. Portrait images don't look very appealing if the tip of the nose is in sharp focus but not the eyes.

Wow, the depth of knowledge displayed here is impressive. The ultimate sharpness of a lens is determined by the quality of the glass and the engineering compromises in it's design.

If you have a good selection of glass and you're pretty sure of your subject distance (and it's not moving), then let the hyperfocal charts be your guide.

I've read several articles on this subject which give the mathematical formulas for determining a lenses sweet spot. But the results almost always turn out like this; for prime lenses half way between the minimum and maximum aperture (which equals f8-f11 for most); for zooms, half the zoom distance at the same apertures.

It's a general rule, but if you shoot several images around those settings one of them should be right on. For the Canon mentioned in the original question, that works out to be 135mm at around f10.

Forgot to mention that the Timex and the 994A used a cassette for storage. The 994A and the PCjr took solid state program cartridges and the jr also had a 5.25" floppy drive.

I don't go quite as far back as the MITS, my first computer was a Timex-Sinclair 1000. I traded it in a year later for a TI-994A, which I still have. Wished I'd kept the Timex too. Moved on to a PCjr. Really considered getting a Mac at the time but the PCjr did color and the Mac was only B&W. Plus the jr was expandable and had a larger software selection including Lotus 123. Moved on to an IBM 55sx and started building my own machines in 2003.

The jury is still out on the longevity of SSD's. They appear to be at least as reliable as mechanical drives and are not as susceptible to physical damage. Most SSD failures involve losing the ability to write new data, but they can still be read. However the electronics can fail and like with HD's when that happens you are out of luck.

Wow, interesting to hear from so many photographers who also roll their own PC's. My experience doesn't go back as far as some here, but as a teenager I was privy to see one of the first supercomputers, an IBM 7090 (I think only three were built at the time). I've used every version of DOS starting with 2.0 and every version of Windows (including the crappy ones)since version 3.0.

My current build uses a hexcore Intel I7 overclocked to 4 GHZ, 32GB RAM and 6TB of storage in a RAID 10 (4 3TB HD's). While not as fast as using SSD's, my boot time is 45 sec. and I don't wait on much of anything. I edit my RAW images in Lightroom and Photoshop. I also use Picasa for quick and dirty jpeg edits.

For photography purposes a mid-range video card works fine, but if your investing in a new system then I recommend a 24" monitor capable of producing the full RGB color gamut. To my knowledge only four models are currently out there and they are kinda pricey but worth it if your doing serious work.

First it is great to be amongst such knowledgeable photographers. 2nd, I apologize for being so full of myself and not checking my facts before writing off the top of my head. I did not intend to sound snippy by suggesting that you all should check the books. But some of you did check and I stand totally corrected.

So to answer the original question, "what is the difference between a prime and a telephoto?" Lets see if I got it right.

Any fixed focal length lens is a prime lens.
A focal length less than 35 (or 50 on full frame)is a wide angle.
Traditionally any lens that is longer than that is a telephoto.
A normal lens is equivalent to a 50 on a 35mm film camera.

I think it is also correct to say that the maximum aperture of a lens does not determine it's sharpness but they often go hand in hand (and so does the cost).

With zoom lenses a constant aperture (say f4) is usually sharper than one with a variable (f3.5-6.3).

Thanks Nikonian72, you are correct about the term "normal," which had slipped my mind in this conversation. I sort of mixed the two together. Normal is the more proper term for a lens that matches the film or sensor size and prime does refer to a fixed lens of any focal length.

Thanks oldtigger, I think Nikon's definition speaks to how much the relationship between camera's, lenses and image size has changed since film days. The 35mm film image was not the only one available, so what would be considered a prime lens for one would be different for another.

A prime for a digital point and shoot might be around 12mm, while for my Nikon it would be about a 24 and for a full frame it would still be a 35.

Today it's either a zoom or not. It just seems easier to say prime instead of fixed focus. But to say you have a 50mm prime lens is sort of redundant, what else would it be?

The question was "what was the sharpest lens you have used?." For me it's my 35 f1.8. No argument with the other lenses suggested here (can't afford the Zeiss ones on a retired man's budget). But at it's price point (and confirmed by lab tests) the Nikor 35 is one of the sharpest lenses out there.

As far as what constitutes a "prime" lens. I stand by the historic definition of the term (check any photography book on the subject). But if you want to call a 300mm lens a prime telephoto, that's OK too.

Hi BigDJim, From your problem description I think that there are two possible issues. 1) Your card reader is flaking out. My experience is that they last only three or four years before the electronics croak, sometimes less. 2) You have one or more corrupted images on the card or the card itself may be failing.

Follow dirtpusher's suggestions or put the card back in the camera and scroll through the pics, look for images that only half display or have a rainbow pattern, delete them and try again.

My sharpest lens is the Nikor 35mm f1.8, followed by my Tamron 60mm f2.0 Macro. The concept of prime lenses vs. telephoto comes from the days of film, a 35mm film camera had a fixed 35mm lens which exactly matched the film image.
Anything with a longer focal length was considered to be a telephoto. In those days zoom lenses were considered to be junk and were only used by amatures.

Today in the world of digital any fixed focal length lens between 35 and 90 is considered to be a prime. Below 35 is considered to be a wide angle and above 90 is a telephoto. Zoom lenses are no longer junk and are usually as sharp as a prime at their middle focal length

Hello to "Like Tulip," you have raised a question that many photographers have faced, it's time to upgrade, but how far do you go? First item, DVD burners are disappearing from most current laptop lines so if a laptop is your choice buy now, optical drives will be gone from them by xmas time.

2nd item, there are no laptop displays that are suitable for serious photo editing, not even Retina displays support the Adobe RGB color gamut. So the question comes down to your level of photography (and how far you intend to pursue it). If your main camera is a point and shoot or the one in your phone or tablet, then any quality laptop or desktop that you can afford will do.

If your using a DSLR and shooting RAW, then buy as much computer power and storage as you can afford. The display you get is critical to good photo editing, a 24" that supports full RGB is recommended. If that is your situation then I suggest that you read David Brooks column in Shutterbug magazine, he has lots of good advice on choosing the monitor (and scanners and printers) for photography.