I am sure that there are others who are computer professionals. But the way that an MIS department in a large corporation solves a problem like the one described by the OP is different from the way that a private party should handle it. After all, a large corporation would own the hardware and software on the computer and have backups and images that could be easily reinstalled. Backing up the data and reimaging would be trivial for an MIS technician.

We need to empathize with the computer amature. The real reason that they justifiably dread reinstalling is that they have no clue what they would be getting themselves into since they have probably never done it before.

I don’t recall whether the OP ever identified the version of Windows he was running. Unless he is running Windows 7, he may even be better off simply buying a new computer .

You and I may follow safe computer practices but the vast majority of home users do not. Getting some good advice from a local professional, face to face, is the best approach.

Would you go to a PC forum to ask for advice on photography? Would you attempt to take apart one of your own cameras or lenses to repair a malfunction? I certainly would not! Neither should you.

Some of the "advice" I have seen in response to your question is, at best, uninformed and much of it is simply wrong and is likely to cost you a lot of money and time.

I have earned my living as a consultant in the software industry for over 40 years. I have reformatted hard drives, installed operating systems (Microsoft and Linux but not Apple) and written software for mainframe and PC computers.

I can assure you that the last thing you want to do is reformat your hard drive and reinstall your operating system and all of your software. Not only will this take several miserable days out of your life, tracking down the licenses an serial numbers may drive you nuts and you might end up having to re-purchase some of your applications.

First, I assume your time is worth something. Get professional help. Take your computer to your local Staples in East Greenwich or ask around for a reputable computer repair/service company. They should be able to get you going again for a reasonable charge without the trouble and expense of reinstalling everything.

Once they have your computer running properly, ask them for recommendations on PC software to keep your computer safe and running properly. Norton or McAfee (either but not both) are worth the investment (about $70/year for up to three PCs) to protect your computer from malware and viruses.

There are reputable registry cleaners available (for about $30 per year) that can help you keep your computer running properly. Get the expert’s advice.

Don't try to fix it yourself! If you were an expert you would not have asked the question. I assume you are not, so don't get in over your head.

Wikipedia: "Bokeh occurs for parts of the scene that lie outside the depth of field." Anyone unfamiliar with the term would look it up. As the depth of field gets shallower, more of the image appears as bokeh, outside of the depth of field, hence, more bokeh.

And the conventional wisdom for FX and 35mm film is that 85mm and up is appropriate as a portrait lens. A Canon 60D has a 1.6 crop factor, so 85mm would equate to 136mm in FX/35mm terms, much longer than the conventional recommendation. For a 1.6 crop factor that equates to about 55mm and up.

The whole point of my post is that the distance to the subject determines whether the features are distorted, not the focal length of the lens.

For what sensor size? FX, DX or smaller? How about MF, 4x5 or 8x10?

As for bokeh, you know what I meant.

As has already been mentioned, this has been discussed many times before. Unfortunately, most of the discussions revolve around which focal length should be used and miss the one significant factor that all formats have in common.

What is most important is not the focal length but the shooting distance. It is the camera to subject distance that renders the correct perspective of a portrait - 10-15 feet is about right. Any closer and the nose becomes larger and the ears smaller. Much further and the features begin to appear flat.

The selection of focal length then determines how much else will be in the picture besides the head. It is OK to use a wide angle lens for a portrait if you want to include more of the environment or a telephoto if what you want is just a head or head and shoulder picture. Something else to consider, a wide angle lens is more likely to keep the background in focus and a telephoto is more likely to give you more bokeh.

There is no right answer. It depends on what you want to show.

Actually, diffraction begins at wide open but the ratio of diffracted light to un-diffracted light only becomes a problem as you reach the diffraction limit. The calculator on that link clearly illustrates this.

For a full-frame 35mm SLR/DSLR the diffraction limit is somewhere between f/16 and f/22. It is lower for a crop sensor DSLR and higher for larger formats, as high as f/90 for 8x10.

For some reason, the link above may not work. Try instead: http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm#calculator This link shows a diffraction limit between f/22 and f/32 for 35mm.

However, as with everything else in photography, it is a matter of degree. The diffraction limit is the point at which the Diameter of Airy Disk exceeds the diameter of the Maximum Circle of Confusion. So, if you assume a larger circle of confusion, you end up with a higher f-stop for the diffraction limit.

There are, of course, a lot of other assumptions you need to consider such as print dimension, viewing distance, your eyesight and camera resolution. Click on advanced to see all of these in the calculator.

A very interesting link! Thanks Jerry.

It is worth spending some time on it and comparing lenses.

I have looked at it for some time and it supports the conventional wisdom that, given the same focal length and aperture:

1. Canon, Nikon and Zeiss lenses appear to have better contrast and edge-to-edge sharpness than the lens-only manufacturers.
2. Fixed focal length lenses are better than zooms.

But what is surprising is how close all of the lenses are between f/5.6 and f/11. Anyone that stays in that range should have no reason to apologize for the amount of money they spent on their lens.

If you agree with the focus point that the camera selects for you, autofocus is fine. If you select the focus point, also OK. But if you hear the focus motor going back and forth (and the subject is not moving), the camera is confused and you should switch to manual focus.

For a stationary object (I assume the camera is also stationary, i.e., on a tripod) you have time to focus manually so you might as well do so.

Good observation. Like everything else in photography, there is a tradeoff between depth of field and diffraction.

Diffraction will begin to show up at about F/22 for a 35mm full-frame image, see http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm. This link contains a handy calculator that shows that it is actually a problem at f/16 for a sensor with a crop factor of 1.5.

Diffraction does not appear suddenly at a specific aperture. The calculator shows that it is independent of focal length but depends on the film format or sensor size.

Norman Koren also gives a thorough mathematical explanation of this in http://www.normankoren.com/Tutorials/MTF6.html although the math may a bit tough to slog through.

He states that "The sweet spot— the range of apertures with excellent sharpness, tends to be between f/5.6 and the aperture corresponding f/11 for the 35mm [full frame] format..." so your selection of f/8 is consistent with his recommendation.

Don't blame the camera. It did not have any trouble with focus on the third shot.

For the first two shots, there are too many possible distances where focus chould have been placed. Any autofocus camera would have had trouble with those shots. And if you were focusing manually, you might also have had trouble deciding.

But not with a rangefinder.

Sounds like you are more than 90% of the way there. You need more understanding of geometry and spatial relationships than you need algebra.

As for algebra, the most complicated thing you need to understand is the inverse square law (don’t let the term intimidate you) that explains how light falls off the further a flash is moved from the subject. Get a grasp of that (and flash guide numbers) and everything else will be straightforward. If the first text does not make it clear, try another one.

The remaining relationships are easier.

This comment comes closer to explaining why the shot looks odd, other than having used a wide angle lens for a "portrait" shot. The problem is not the geometry of the picture, some of which can be fixed with leveling or cropping.

The issue with the lighting is the color temperature of the flash (daylight) compared to the sunset. They are so different that they do not seem to belong together. Also, having the sun right behind her head emphasizes the difference.

I know that some of you may not like some of Ken Rockwell's views on equipment, but he makes many valid points in his November 2012 article: http://www.kenrockwell.com/tech/why-we-love-film.htm

It's a long article worth reading - he seems to have checked all of the boxes.

Your priorities are different from mine. I do my own B&W processing for 35mm, 120 and 4x5 and then scan it myself. I can afford to have my color developed in a lab because I don't need to update my digital equiment very often.

When I need to take hundreds of snapshots I used my D70 or a D7000 and for convenience I can use my smart phone or Coolpix.

It's good to have a choice.