# Digital Camera Buyer’s Guide: Introduction

First, congratulations! Camera technology has advanced to the point where a complete novice, using an entry-level camera right out of the box, can take photos that (under certain circumstances) appear identical to professional photos. Regardless if you only use your camera on the ‘automatic’ setting or if you explore the art of photography, the most important part of any photograph is *you*- your brain and your eyes. To paraphrase, cameras don’t take good pictures, people do. So, to the question at hand-

It depends. The best camera for you is the camera that meets your needs. While PF cannot recommend a specific camera (for various reasons), we can provide technical information that will help you better understand the specific product reviews contained in other review sites. This sticky is organized in terms of expertise- starting with zero and working up to expert. You will see that certain topics are re-visited because imaging involves certain technical trade-offs inherent in the relevant physics. PF has a dedicated group of enthusiasts who are happy to help you take better pictures!

A couple preliminaries and definitions: ‘lens’ refers to the hunk of glass/plastic on the front of a camera that may be made up of multiple elements, and is rotationally symmetric about the ‘optical axis’. ‘Sensor’ refers to the light-detecting chip. ‘Imaging’ means the same thing as ‘taking a picture’. ’35mm format’ refers to the standard (135 film) camera format. It can be helpful to be aware of the 35mm format, because much of the nomenclature is derived from 35mm film cameras. The phrase ’35mm film format’ is associated with the Kodak 135 film frame size (ISO 1007). This image frame size is 36mm x 24 mm, with a diagonal dimension of 43 mm.

Table of contents: Each section represents a general class of photographer (i.e. you), and the associated lists of topics are organized based on what you need to know to make a rational choice when purchasing a camera.

I’ve never owned a camera (besides what is in my cell phone and laptop). I want to take pictures at parties and post them online or email them to my friends.

Basic Definitions
What’s so special about digital cameras?
Half-press
Bayer filter
Flash
Gain
Dynamic Range
Optical v. digital zoom
White balance
Live preview
Image stabilization
Shooting modes
Video

I’ve never owned a camera, but I want to get a ‘real’ camera (that doesn’t cost too much).
I’ve owned an entry-level camera already and I want to take the next step.

Focal length
f-stop
Exposure time
Resolution
Crop Factor
Depth of field
ISO
Exposure bracketing
Frame rate
Histogram
Post-processing
Pixel size
Macro imaging
Autofocus
Sharpness
Memory cards

Lens classifications
Lens aberrations
Falloff
Flare
Bokeh
Image stabilization
Filters
Rule of 16
Hyperfocal distance
Focal/principal/nodal points
Miscellany

Look for Part 2 coming in the next few days!

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75 replies
1. Andre says:

As I said earlier, buying an SLR is like marrying to that particular brand. Sooner or later more lenses are added in the inventory and then it's getting real tough to switch brands. Therefore looking at possible future desired lenses could assist, taking decisions.

2. Topher925 says:

I spent at least a good hour the other day checking out the A77 photos on dpreview and comparing to other camera's I'm looking at. While the JPEGs are questionable, the RAW files definitely bring out the shortcomings of the Sony 24MP sensor. I think I can cross that one off the list given the type of photos I want to take. I've been looking closely at the d5100 for a long time now, it truly is a fantastic camera for money. The fit and finish could be a bit nicer but for the price its acceptable. If I end up not getting the k-5 I'll most likely pick up the d5100.

3. Andre says:

Yes the D700 is very good at high ISO and outperforms the 5D MKII on some other things as well, except image detail/resolution due to only 12.1 MP versus 21.1MP. If you reduce the image size to the same 12.1 MP, you also reduce noise, while maintaining detail. I also should add that Andy's Sony A900 has the best resolution/detail but cannot keep up at higher ISOTo Topher925, you can find unlimited discussions here about the Sony A65/77http://forums.dpreview.com/forums/forum.asp?forum=1037

4. khemist says:

[quote="Andre, post: 3523795"]yes you are right noise is an issue with the new Sony's. Obviously with a fixed translucent mirror you lose some light going to the main sensor. So it's plain physics that signal to noise ratio is worse. However the 25 mp of the A77 reduces that problem somewhat if you reduce the output to 16MP. Another issue would be hot pixels, that emerge at long shutter speeds and high ISO, same problem there.The best signal to noise ration in relation to its price in DSLR's comes from the Canon 5D mkII (21 mp) especially at high ISO. The best absolute high ISO S/N ratio comes form the Nikon D3S (12mp) but at about double the price.[/QUOTE]The Nikon D700 has much better noise reduction for the same price point as a mark 2. However, they are both outstanding cameras.Interestingly enough, the higher MP the mark 2 has contributes to the increased noise. My friend will shoot at ISO 6000 with the mark 2 and still get relatively noise free shots, but in comparison tests I have seen the d700 has less noise at almost all ISO levels.

5. Andre says:

[quote="Topher925, post: 3522550"]What is everyone's opinion of the Sony SLT A65 & 77 being released next month? I'm in the market for a new camera and so far have been looking at the Pentax k-5 for its low light performance and star tracker GPS thing. But with the A65 having such impressive specs for such a low price I'm really considering it instead.My only concern is low light performance. Given that its an SLT with ~2/3 of the light actually hitting the sensor coupled with the sensor having a very small pixel pitch makes me think that low light performance/noise will be rather poor compared to the k-5. Sony also limits the ISO to 16000. Whichever camera I buy a lot of its time will be spent doing some lite astrophotography so high noise is a big concern.[/QUOTE]yes you are right noise is an issue with the new Sony's. Obviously with a fixed translucent mirror you lose some light going to the main sensor. So it's plain physics that signal to noise ratio is worse. However the 25 mp of the A77 reduces that problem somewhat if you reduce the output to 16MP. Another issue would be hot pixels, that emerge at long shutter speeds and high ISO, same problem there.The best signal to noise ration in relation to its price in DSLR's comes from the Canon 5D mkII (21 mp) especially at high ISO. The best absolute high ISO S/N ratio comes form the Nikon D3S (12mp) but at about double the price.

6. Andy Resnick says:

I don't recommend specific products- nobody pays me or provides equipment to use- but if your highest priority is low-light-level imaging, then you are right to carefully examine that spec.

7. Topher925 says:

What is everyone's opinion of the Sony SLT A65 & 77 being released next month? I'm in the market for a new camera and so far have been looking at the Pentax k-5 for its low light performance and star tracker GPS thing. But with the A65 having such impressive specs for such a low price I'm really considering it instead.My only concern is low light performance. Given that its an SLT with ~2/3 of the light actually hitting the sensor coupled with the sensor having a very small pixel pitch makes me think that low light performance/noise will be rather poor compared to the k-5. Sony also limits the ISO to 16000. Whichever camera I buy a lot of its time will be spent doing some lite astrophotography so high noise is a big concern.

8. Andy Resnick says:

[quote="Borek, post: 3257580"]I understand value of 1.6m for 28/8 can be calculated assuming circle of confusion of 0.03 mm and the 'real' focal length. Thats for a full frame camera. What values would be reasonable for APS-C?[/QUOTE]Sorry- I didn't see this when you posted it.  Varying the image size means the circle of confusion must be scaled (just as the focal length must be scaled). If the APS-C has a crop factor of say, 1.5x, the CoC is also divided by 1.5x so it would be 0.02 mm.The CoC specification was originally determined by using a standard enlargement of 8x viewed at 25cm; the reality is that viewing conditions and acuity affect the result.One counter-intuitive result (for me, anyways) is that larger format images (4" x 5" or even 8" x 10") appear sharper and have a more narrow depth of field than 35mm images.

9. Andre says:

I think that is worth some empirical trial and error [strike]work[/strike] fun.

10. Borek says:

[quote="Andre, post: 3257622"]So it seems that you get the oxymoron that the better the camera resolution, the less the depth of field and the farther away the hyperfocal distance.[/QUOTE]That's why I asked for "reasonable"…

11. Andre says:

[quote="Borek, post: 3257580"]I understand value of 1.6m for 28/8 can be calculated assuming circle of confusion of 0.03 mm and the 'real' focal length. Thats for a full frame camera. What values would be reasonable for APS-C?[/QUOTE]I guess if you don't change other facters that the crop factor 1.6 for Canon applies, hence 0.02 (0.01875).Mind that a CoC of 0.03 mm on a 24mm height compares to a resolution of 800 LPH (lines per height). However modern full frames easily get to 2500 LPH. So it seems that you get the oxymoron that the better the camera resolution, the less the depth of field and the farther away the hyperfocal distance.

12. Borek says:

[quote="Andy Resnick, post: 3091602"]Hyperfocal distance: The hyperfocal distance is calculated by maximizing the depth of field: when a lens is focused at the hyperfocal distance, objects from infinity to half the hyperfocal distance are rendered in focus.   The analytic result is: $$H = f( frac{f}{Fc}+1)$$,where H is the hyperfocal distance, f the focal length, F the f-number, and c the diameter of the circle of confusion. The hyperfocal distance also forms a series solution: focusing the lens at 1/2 the hyperfocal distance renders objects from the hyperfocal distance to 1/3 the hyperfocal distance in focus; focusing at 1/3 the hyperfocal distance covers objects from 1/2 to 1/4 the hyperfocal distance, etc.  For example, the hyperfocal distance for a 28mm lens set to f/16 on a 35mm camera is about 1.6m. Everything from 0.8m to infinity will be sharp in a photograph taken with this lens focused at an object 1.6m away.[/QUOTE]I understand value of 1.6m for 28/8 can be calculated assuming circle of confusion of 0.03 mm and the 'real' focal length. Thats for a full frame camera. What values would be reasonable for APS-C?

13. Andre says:

Just wanted to tell that the new micro four thirds system (cropfactor 2) is maturing. A big leap ahead is made with the Panasonic GH2, from preliminary results I see that the image quality is excellent, on par or better than most of the APC-C format cameras (crop factor 1.5 / 1.6)  like the CANON EOS7D or the Nikon D7000, that is on low ISO's. On higher ISO's -as expected- the image noise is clearly worse albeit that the image remains tack sharp.Micro four third cameras are hybrids half way between upper end point and shoot cameras and DSLR. The lens is exchangable but there is no mirror.It's not cheap though.

14. turbo says:

[quote="jtbell, post: 3091637"]Prior to the digital era, most film SLRs had automatic light-metering and many had autofocusing. When I bought a Pentax K1000 around 1990, it was one of only a few completely-manual SLRs still available, if I remember correctly.[/QUOTE]I had a large stable of Olympus OM-1s and a single OM-4 with Zuicko prime lenses.  I had two OM-1s that were dedicated to astrophotography.  They were both dirt cheap at pawn shops because the meters didn't work.  I think I paid \$20 each for them.  Still, they had manual shutters, mirror lock-up, interchangeable focus screens, and other features that made them perfect for astro-imaging.  Plus, the OM series was smaller and lighter than about any other pro-grade SLR.

15. Andy Resnick says:

[quote="Greg Bernhardt, post: 3143917"]Just saw this now.  Great work Andy![/QUOTE]Thanks, but I can't take all the credit- call me the 'lead author'. It was a collaborative effort from 3 or 4 of us (who can choose to identify themselves if they wish).

16. Andre says:

I still have my Minolta XD7 and some lenses. So when I decided to go serious on photography again, selecting a DSLR, I first considered Sony/Minolta because my lenses may still be useable.But nope. Also lenses seem to age. Nothing automatic in there. I finally went for the Canon EOS 450D back in April 2008 because of superior image quality at that time.

17. Andy Resnick says:

I had a Nikon FG; no autofocus, but it did have metering (no autoexposure- I had to set the shutter speed and/or aperture manually). In addition, it had a full manual mode- if the battery was dead, for example- that provided a fixed 1/90 s shutter speed.

18. jtbell says:

[quote="Andy Resnick, post: 3091595"]What makes a digital camera special? […]  A second key difference is what happens when you press the button to take a picture.  In manual cameras, not much happens- a mechanical shutter opens for a set amount of time, exposing the film, and then closes.  Digital cameras do a lot of things when that button is depressed, including light metering and focusing,[/QUOTE]Prior to the digital era, most film SLRs had automatic light-metering and many had autofocusing. When I bought a Pentax K1000 around 1990, it was one of only a few completely-manual SLRs still available, if I remember correctly.