# Insights Digital Camera Buyer's Guide Introduction - Comments

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#### jtbell

Mentor
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,
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.

#### Andy Resnick

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.

#### Andre

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.

#### Greg Bernhardt

Just saw this now. Great work Andy!

#### Andy Resnick

Just saw this now. Great work Andy!
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).

#### turbo

Gold Member
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.
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.

#### Andre

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.

#### Borek

Mentor
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.
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?

#### Andre

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?
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.

#### Borek

Mentor
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.
That's why I asked for "reasonable"...

#### Andre

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

#### Andy Resnick

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?
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.

#### Topher925

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.

#### Andy Resnick

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.

#### Andre

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.
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.

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#### khemist

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.
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.

#### Andre

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 ISO

To Topher925, you can find unlimited discussions here about the Sony A65/77
http://forums.dpreview.com/forums/forum.asp?forum=1037

#### Andre

What is everyone's opinion of the Sony SLT A65 & 77 being released next month? .... Whichever camera I buy a lot of its time will be spent doing some lite astrophotography so high noise is a big concern.
Here are more answers, dpreview has made test shots available with the A77. So if you go to any test, like this of the Canon 60D then you can compare crops of many cameras on this page (in RAW).

In the individual drop down menus you can select available cameras (I selected Sony A77, Nikon D5100, and Canon 5D mkII) you can also select ISO and the crop to compare.

So I went to ISO 3200 and selected a grey area for better noise comparison:

I would consider the Sony A77 a bit underwhelming. The Canon 5D mk II clearly leads the pack, while the Nikon D5100 is slightly better than the three year older sensor of the Canon EOS 60D.

Maybe the Nikon D5100 should be in the very short list of least noise for the best price.

#### Topher925

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.

#### Andre

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.

#### Andre

Anyway, this is one of my favorite crops:

Notice that the K-5 is excellent for noise but moderate on resolution detail. Notice also that the Canon 600D (Rebel T3i), sharing the sensor with the 60D and 7D, is just outperforming the D5100 with half a notch on details, despite the slightly worse performance on noise.

#### khemist

Just another tip. The MP doesnt really matter. Any camera nowadays will be able to perform fine. Unless you blow up your photos to poster size, no one will be able to tell the difference.

To be honest, get nice glass over a nice body. A sharp lens can make an aging camera come back to life.

And in the end, whatever camera you buy will work. It will have the ability to take good pictures, but its really who is behind the camera that really matters.

#### Andre

Just another tip. The MP doesnt really matter. Any camera nowadays will be able to perform fine. Unless you blow up your photos to poster size, no one will be able to tell the difference.
The disadvantage of high MP is noise, but the advantage is that you can crop more, getting more effective focal lenght from your glass.

To be honest, get nice glass over a nice body. A sharp lens can make an aging camera come back to life.
Nicer bodies will still make that picture, where others can't, especially in high dynamic situations, you'll soon learn the difference.
Edit: Like these for instance. and this...

And better glass is not necesarily more expensive glass. Moreover, if you want from excellent glass to splendid glass, you pay a nice body more.

but its really who is behind the camera that really matters.
Absolutely

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#### turbo

Gold Member
To be honest, get nice glass over a nice body. A sharp lens can make an aging camera come back to life.

And in the end, whatever camera you buy will work. It will have the ability to take good pictures, but its really who is behind the camera that really matters.
All true, and as Andre said above, one should select a system, not just a camera. Once you start adding high-end lenses to your kit, and maybe another camera body, you'll have an "investment" that is hard to recoup if you decide to switch brands.

I decided that I liked the Canon brand, and liked their line-up of lenses so I started out there. Now, I have two 30D bodies and a selection of lenses, including a 100-400 L. I have not felt a driving need (or even want) to upgrade. The quality of this equipment is incredible, and the biggest limitation in the system is the "nut behind the wheel" (myself). Yes, there are shutterbugs who will try to stay on the bleeding edge, but that is expensive, even if you stay within your brand and chase body upgrades so you can keep using that expensive glass. Andre's shots have tempted me to consider a 100mm macro, but I shoot macro so infrequently that I have resisted the urge to splurge.

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