Simple f-stop question I can't find an answer to

[jrh312]

I'm looking into buying my first dslr and one of my priorities is that I want to be able to go with a smaller aperture than my current camera (f/8.0). Is that determined by the lens or by the camera?

The reason I'm asking is that I'm seeing it on specs for some cameras but not others.

Thanks

[JeffreyG]

The aperture in a dSLR is a function of the lens. In most cases, we are interested in the maximum aperture (lowest number) which gives shallow depth of field and lets in more light.

There are also limits to smallest aperture (highest number), but most photpgraphers prefer not to shoot against the equipment limits in this direction. Using very small apertures (like f/22 and higher) will require very long shutter times, will deliver very great depth of field and will soften the image because of diffraction effects.

What constitutes a 'very small' aperture is also dependent on the sensor size. An aperture like f/8 is a really small one for a P&S camera while it is middle of the road for a 35mm dSLR.

To understand apertures look at how to read them. Some common Canon lenses:

EF 35 1:1.4L USM = 35mm prime (non-zooming) lens with a maximum aperture of f/1.4. This lens can be used between f/1.4 and some upper limit that is typically published in a spec sheet. For a fast lens like the 35/1.4, the upper limit is usually f/16 to f/22.

EF 70-200 1:4 USM = 70mm to 200mm prime lens that has a maximum aperture of f/4 across the whole zoom range. The lens can be used between f/4 and f/32.

EF 70-300 1:4-5.6 IS USM = 70mm to 300mm zoom lens with a variable maximum aperture. Do not be fooled by that f/4-f/5.6 range, f/5.6 is not the smallest aperture this lens can reach. It is the maximum aperture that can be used at the long end of the zoom range. So the lens is an f/4 max at 70mm and f/5.6 max at 300mm.

[Dchemist]

The Lens. If you are buying a camera with an attached lens then the camera specs may mention the aperture range or the printing on the lens may show it. If you buy a DSLR and lens seperately the lens specs will show what aperture it offers.

[jrh312]

hmm... maybe I will stick with a P&S again then. I'm not really in the best spot financially to buy a camera and another big lens right now. I kinda feel like I've outgrown my camera, but part of that is the resolution I'm sure (it's a 2.something megapixel). I know pixels aren't everything, and there's a lot I like about my camera (Panasonic DMC-FZ3), but I feel limited....

[JeffreyG]

hmm... maybe I will stick with a P&S again then. I'm not really in the best spot financially to buy a camera and another big lens right now. I kinda feel like I've outgrown my camera, but part of that is the resolution I'm sure (it's a 2.something megapixel). I know pixels aren't everything, and there's a lot I like about my camera (Panasonic DMC-FZ3), but I feel limited....

1) I'll go look up your Panasonic's specs, but in the meanwhile...

2) When you say you want a camera capable of more than f/8, what are you specifically trying to accomplish? Low light shooting? Shallow depth of field? Deep depth of field?

Give us some specifics and we can recommend either how to do it with what you have, or what else might work.

[jrh312]

It's the Panasonic DMC-FZ3 I mentioned above. I'd like to have a deeper depth of field.... my camera ranges from f/2.8 to f/8 and I'm actually really surprised that it's the wider end of the range that's more sought after. I can't think of a time when I've wanted to go shallower than that.

[JeffreyG]

It's the Panasonic DMC-FZ3 I mentioned above. I'd like to have a deeper depth of field.... my camera ranges from f/2.8 to f/8 and I'm actually really surprised that it's the wider end of the range that's more sought after. I can't think of a time when I've wanted to go shallower than that.

Are you shooting macros?

Your Panasonic has a very tiny little sensor, which means that the actual lens range for the camera uses very short focal lengths. There are two reasons Panasonic limited your lens to f/8.

1) Because your focal lengths are very short, f/8 gives functionally massive depth of field. You might find that f/8 on your little Panny delivers DOF like f/22 or even more might on a dSLR.
2) Again with the small sensor, you are physically enlarging the image from sensor to print a lot more for a given print size on the Panny than you would with a much larger dSLR sensor. This all means that diffraction will soften your image at a larger aperture than it will on a dSLR. You really probably don't want to be using apertures much smaller than f/8 as the whole picture will start to get soft.

Do you have any examples of shots where you want more DOF?

[jrh312]

Are you shooting macros?

Your Panasonic has a very tiny little sensor, which means that the actual lens range for the camera uses very short focal lengths. There are two reasons Panasonic limited your lens to f/8.

1) Because your focal lengths are very short, f/8 gives functionally massive depth of field. You might find that f/8 on your little Panny delivers DOF like f/22 or even more might on a dSLR.
2) Again with the small sensor, you are physically enlarging the image from sensor to print a lot more for a given print size on the Panny than you would with a much larger dSLR sensor. This all means that diffraction will soften your image at a larger aperture than it will on a dSLR. You really probably don't want to be using apertures much smaller than f/8 as the whole picture will start to get soft.

Do you have any examples of shots where you want more DOF?

That's a good point... see it's these things about the differences between dSLRs and P&S cameras that I don't know. I would have assumed they were the same because both were digital.

Here's an old example of something I'd like to see with more DOF. I know it's not terrible, but it still seems soft in parts I'd like to see in focus.

http://i6.photobucket.com/albums/y215/jrh312/Outdoor/Waterfalls/July262005031crop-resize.jpg

The more I think about it, and with your comments above, I wonder how much of what I'm seeing as soft because of DOF is actually soft because of zoom and sensor size. As it stands now, if I zoom all the way in to 12x optical, the whole thing is soft even with no wind and a sturdy tripod. I can't hook a shutter cable to this camera, so I use the timer for stuff like that.

This might be a huge question with a longwinded answer (and if so, feel free to point me in the direction of a website that explains it), but how does sensor size affect image quality? Obviously bigger is better, but how much of a difference in quality would I expect to see for a given difference in sensor size? This aspect of photography is totally new to me...

[JeffreyG]

Sensor size has a strong effect on image quality. The main reason for this is because the larger the sensor, the less you are enlarging the physical image captured from sensor to print. This in turn means you are physically enlarging the tiny details resolved by the lens more. This (sensor size) is one of the main reasons that dSLRs can create better large prints.

Let me see if I can find you a few links for in depth reading. I think a cheap dSLR like an older XSi or even XTi with some competent affordable lenses like the EF-S 18-55 IS and the EF-S 55-250 IS might be very nice for you.

[JeffreyG]

Here's a few. These are all a few years old, but really nothing has actually changed in cameras in the last 5-8 years except they are all better now.

http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

http://www.luminous-landscape.com/essays/sensor-design.shtml

http://photo.net/equipment/digital/sensorsize/

[jrh312]

Thanks, I'll check these out. I've been putting off grading papers all night and i should probably get on that, but I'll take a look late tonight or tomorrow...lol

[jrh312]

Here's a few. These are all a few years old, but really nothing has actually changed in cameras in the last 5-8 years except they are all better now.

http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

http://www.luminous-landscape.com/essays/sensor-design.shtml

http://photo.net/equipment/digital/sensorsize/


I've read the articles, and have been researching a few other cameras over the past couple of days and I found another interesting one. What you've said about sensor size has definitely persuaded me to look more at that and less at aperture size, which was my original priority for a new camera.

For cost reasons, I do think I might stick with a P&S camera, but I did find one with a ~22mm x 14mm CMOS sensor that is (according to Sony) apparently only slightly smaller than their entry model dSLRs.

The one I'm looking at now is the Cybershot DSC-R1 (http://www.dpreview.com/reviews/sonydscr1/) . It inched out Canon's G10 once I saw the size of the sensors in each. As a bonus, the Sony goes to f/16, which might be fun even though it's not really a priority anymore. I'm not a huge fan of the LCD being on top of the camera, but I think I could get over that.

I won't get a camera for a month or two, so I'm going to try to do some comparisons against the Sony and I'm not ruling out dSLRs completely yet.

Any thoughts on this one?

[gonzogolf]

I've read the articles, and have been researching a few other cameras over the past couple of days and I found another interesting one. What you've said about sensor size has definitely persuaded me to look more at that and less at aperture size, which was my original priority for a new camera.

For cost reasons, I do think I might stick with a P&S camera, but I did find one with a ~22mm x 14mm CMOS sensor that is (according to Sony) apparently only slightly smaller than their entry model dSLRs.

The one I'm looking at now is the Cybershot DSC-R1 (http://www.dpreview.com/reviews/sonydscr1/) . It inched out Canon's G10 once I saw the size of the sensors in each. As a bonus, the Sony goes to f/16, which might be fun even though it's not really a priority anymore. I'm not a huge fan of the LCD being on top of the camera, but I think I could get over that.

I won't get a camera for a month or two, so I'm going to try to do some comparisons against the Sony and I'm not ruling out dSLRs completely yet.

Any thoughts on this one?
I think if you ever got your hands wrapped around a dslr and looked into the image rather than at it on a shiny screen you would be hooked. That and the ability to change lenses to fit the appropriate task make all the difference in the world.

[jrh312]

Maybe, but isn't even an entry level dSLR and a basic lens ~$1000. That's two weeks' pay for me (who says being a teacher isn't fulfilling? lol)

Do you have any suggestions for a decent dSLR that won't break the bank?

[k_wakasugi]

Used 20D and 18-55 IS kit lens could be had for under $400 here on this forum in the buy and sell section. That's a decent setup that won't break the bank.

[gonzogolf]

Maybe, but isn't even an entry level dSLR and a basic lens ~$1000. That's two weeks' pay for me (who says being a teacher isn't fulfilling? lol)

Do you have any suggestions for a decent dSLR that won't break the bank? You can get a entry level dslr (canon xs) for right at $550 or so. That includes an image stabilized lens 18-55 is. If I were guiding you I would look for a used 30D ($350 or so) or 40D ($500ish) and pick up that same lens used for another hundred. I'm not sure what your sony is priced at, but the joy of a dslr is you are buying into a system where you can swap out obsolete bodies and still retain functionality with the lenses and flashes. When the sony gets old, you start over from scratch.

[jrh312]

That's true... those aren't too pricey either. The Sony started out at ~$1000 when it was new, but is going for about 300 now.

I'll look into those and do some comparisons.

[JeffreyG]

The best IQ vs. value right now is in the entry level dSLRs, especially if you do not need high speed performance in AF and frame rate for sports etc.