A bit of revision, since I was asked this three times in the last few days. “Why are F-stops important?” Yes – repeat answer, but important enough to repeat, I think. So here goes.

F-stops (the clicks on the aperture adjustment ring on old cameras, hence “stops”) are important. You know: f/5.6, f/8, f/11, that sort of thing. Or on a good lens, maybe f/2.8, or for a prime (non-adjustable) lens, even lower. The lower a lens can go, the better.

Why?

• The lower the f-stop (it is “f divided by that number”), the larger the diameter of the lens opening while the picture is being taken.
• In other words, “lower f-number” equals “larger lens opening”.
• The main f-numbers (16, 11, 8, 5.6, 4, 2.8, 2, 1,4…) mean twice as much light each time you go to a smaller number.
• (That is why the ratio between these numbers is the square root of 2: after all, since the area of a circle equals pi x r squared, to halve the light that comes in you must reduce the diameter of a circle by the square root of 2)

This means two things:

• That lower f-number means that more light gets in. Hence, you get the ability to take pictures in lower-light conditions at the same ISO. See yesterday’s post for why that is important.
• The low f-number also means blurrier backgrounds. The wider the lens, the more paths an out-of-focus part of the picture can follow to reach the sensor; hence, the blurrier that out-of-focus element becomes.

Blurry backgrounds and low-light pictures are good things. So look at the front or top of your lens. If the lens says “1:3.5-5.6″ it is a kit lens that can open to f/3.5 at wide angle and f/5.6 when zoomed in. A pro zoom lens will just say 1:2.8”.

And the new 50mm prime lens I am buying, used, tomorrow says 1:1.2, meaning f/1.2 – meaning it is faster (more light gets in) than the 1.4 lens I now have.

Alas, more light means more glass, and hence more dollars. But you will see why this is worth it.

In general, get the fastest lens you can get, if you can afford it.

A reader asks this, and I thought I would make this today’s post:

I read your wonderful blog everyday, and I learned many thing about flash photography.

I am 53 y. old and I ‘d like to get a 1D camera once in my life. I am debating if I need to change my camera, a canon 50D, with the new 1D Mk IV.

I am not a pro; I own many crop lenses ( 17-55mm f2.8 is – 15-85mm is – 10-22mm 60mm macro).

My other camera is a full frame 5D old with 17-40mm, 70-200mm f4 is, 24-105mm f4 is, plus 2 canon flash 430 and 580 II. I am selling some stuff and I have now 2200€= than I could sell all my crop material and finally buy my dream with some more new lens.

What I am asking, in your opinion ..WORTH IT ? or is better to sell the old 5D and buy a less expensive new 5D mk II…?

Thank you!
Regards from Italy – Adalberto

Adalberto: great question.

Always great to hear from Italy: I lived in Rome for about a year in the 1980s, e mi manca l’Italia – tanto. La cucina Italiana; Roma; le donne; il vino; le macchine; mi mancano queste cose.

Anyway, back to cameras. This is a question we all wrestle with: Do we buy a better camera, or spend our money on lenses and so on? Which camera? I have a 1Ds Mark III, a 1D Mk IV, and a 7D, and I used to own a 5D, so I can probably say some sensible things about this choice.

First, there is the choice “crop or not crop”? A crop camera is a camera with a smaller sensor. Crop is cheaper, and can use cheaper lenses; but “full frame” (like a 5D or 1Ds) or “almost full frame” (like a 1D, which has a 1.3 crop) is better than the usual 1.6 (or for Nikon, 1.5) crop:

1. Wide angle is wider!
2. Lower noise, so easier to use at high ISO values.
3. Narrower depth of field (“Blurrier backgrounds”).
4. Bigger, brighter viewfinder.

So yes, full frame or near full frame is better.

Then there is the choice of body type: an amateur body (50D), a lower-end pro body (5D), or a pro body (1Dx)? A pro body does not take better pictures. But it is more waterproof; it has more settings; it can write to two memory cards at once; it will last 300,000 shutter releases instead of 150,000 shutter releases: all great things.

In your case, I would ask:

1. Do I need a full frame or near full frame body?
2. Do I need a pro 1-series body?

As for question one: yes, if I were you, I would go all full (or almost full) frame, and sell your crop lenses, if I had that budget. Sell the crop lenses, would be my advice, and sell the 50D while it has value.

As for question two:

• a 5D MkII is a great camera.
• A 1D Mk IV, an “almost full frame” camera, is great also.
• A 1Ds is greater still, being full frame, but it is getting old and will be replaced soon by a 1Ds Mk IV.

In general,

Lenses are more important than the camera

…so perhaps a 5D and some f/2.8 lenses, and maybe a prime or two, would be a good way to go?

On the other hand.. I know the excitement that a really great body gives. If you really want a 1-body, get one. A 1D Mark IV.

Ask yourself:

• Do I shoot sports a lot?
• Do I shoot in bad weather, like rain?
• Do I need fast performance?
• Do I take a lot of pictures?
• Do I shoot ultra-important things like weddings?
• Do I charge for my work, so I need to look the part?

If you answer “yes” to even a few of those, get a 1D and a 50mm f/1.4 lens. If not, you can get a 5D Mark II and some more lenses. That is my advice.

But you cannot go wrong: all the equipment and cameras you are looking for are great. So whatever you do, you will do well. And DO get a 50mm f/1.4 lens, or even the 50mm f/1.8!