A couple more pix from the A900

[Dr. Harout]

These problems are common enough in Canon 1Ds models so it would not be surprising to see it happen in an A900 - though so far, they seem better made.

David

How I love to hear things like this

[InTheSky]

Thanks a lot David, i will tried this tonight.

I have found that with the 28mm F/2.0, it looks like that the corner looks better. But it is true that the right end looks all the time a little bit worse ...

Regards,

Frank

[David Kilpatrick]

It was also the right hand end which looks worse with the A900 I tried in Edinburgh. Sensors are mounted in a certain way, and a consistent tendency for the right hand end to be a few angstroms closer to the lens than the left side could happen.

To check this, find some patterned carpet or floorboards or paving stones then angle the camera down a bit and take a view of them, vertical, centre of frame focused on 2m from standing eyelevel position at f2.8, with the camera held one way up. Now repeat the shot exactly with the camera held the other way up. If you see a clear difference in the way the depth of field extends in front of the focus position, the sensor/lens alignment is out of parallel.

David

[bakubo]

My first KM 7D bought in March 2005 turned out to have a sensor that was not perfectly perpendicular to the lens. At first I thought it was having focusing problems, but then I mounted it on a tripod and carefully did the brick wall test with multiple lenses. All of them had the top half out of focus, but the bottom half in focus (or maybe it was the other way around). KM, with the kind help of Phil Bradon at KM New Jersey, replaced it with another 7D.

[shadowfax]

Nice view, but I would like to some pics that actually highlight the A900.

I have put the full resolution version of this shot on pBase, downloadable:


http://www.pbase.com/davidkilpatrick/image/104521336
with no black border or size reduction as the previous one. I have printed this tonight at 20 x 16 size and there's no way you could get this quality, short of using 6 x 9cm rollfilm, in the darkroom. I wish I could show you the print, but if you download the image, and have an Epson 3880 or similar large printer, try it.

Also, a driftwood shot - what superb driftwood - this is the kind of wood I would harvest if I was making musical instruments or carving ornaments!


http://www.pbase.com/davidkilpatrick/image/104521554
Also downloadable at full resolution. f/16 at 50mm on the 28-75mm.

Here are some thoughts - the 17-35 and 28-75mm need stopping down for best results. The A900 needs stopping down to get adequate depth of field for many shots. So, owning a 24-70mm CZ which is more useful wide open is not so valuable; at apertures like f4 or f8, or even f11, there is often just not enough depth of field. But - if you want fantastic differential focus effects, nothing works better than primes like the 50mm f1.4 or 100mm macro f2.8 (or indeed, 80-200mm f2.8 and 70-200mm f2.. So, I am not missing the 24-70mm.

Warning - the A900 is not necessarily a step up from the A700. To get the same depth of field at the same angle of view (i.e. 28mm instead of 17mm etc) you need 1.5 stops smaller aperture. That means using ISO 200-400 instead of 100, or ISO 400-800 instead of 200. And, it means that you need to change your habits. Program setting works fine on the A700, usually there is enough depth of field. On the A900, Program generally uses too wide an aperture. So does flash, where you have no choice over aperture unless you boost the ISO. I love the A900 but I am not blind to the reasons why it is NOT the right solution for everyday shooting!

David

[picman]

Here are some thoughts - the 17-35 and 28-75mm need stopping down for best results. The A900 needs stopping down to get adequate depth of field for many shots. So, owning a 24-70mm CZ which is more useful wide open is not so valuable; at apertures like f4 or f8, or even f11, there is often just not enough depth of field. But - if you want fantastic differential focus effects, nothing works better than primes like the 50mm f1.4 or 100mm macro f2.8 (or indeed, 80-200mm f2.8 and 70-200mm f2.. So, I am not missing the 24-70mm.

Warning - the A900 is not necessarily a step up from the A700. To get the same depth of field at the same angle of view (i.e. 28mm instead of 17mm etc) you need 1.5 stops smaller aperture. That means using ISO 200-400 instead of 100, or ISO 400-800 instead of 200. And, it means that you need to change your habits. Program setting works fine on the A700, usually there is enough depth of field. On the A900, Program generally uses too wide an aperture. So does flash, where you have no choice over aperture unless you boost the ISO. I love the A900 but I am not blind to the reasons why it is NOT the right solution for everyday shooting!

David

I don't get this. I have been using large aperture Zeiss lenses on my Contax system for years with great results. Why all of a sudden is the CZ 24-70, which apparently was made for full frame no longer so useful? Reduced depth of field can be very artistic, and if you want more depth of field you stop down. So what is the problem?

[David Kilpatrick]

I don't get this. I have been using large aperture Zeiss lenses on my Contax system for years with great results. Why all of a sudden is the CZ 24-70, which apparently was made for full frame no longer so useful? Reduced depth of field can be very artistic, and if you want more depth of field you stop down. So what is the problem?

A good example is that I attended some photographic awards yesterday. To get photos of the presentations, it was necessary to work at f5.6 and ISO 400 with flash. When you have two or three people in a small group, not all lined up in a straight row, you need enough depth of field for the faces to all be sharp. I took the A700, not the A900, because for the same crop/angle of view, f5.6 and the shorter focal length involved is as good as using f9.5 on the A900 - and flash photos at 400 on the A700 look fine, they are not so wonderful at ISO 1000 on the A900. Reduced depth if field can be very artistic as you say, but it can also render a commercially shot image unsatisfactory for the intended use.

There is no 'problem', it's just there are different solutions to get the required results - one of those solutions is to use APS-C for certain types of photography where an extra 1.5 stops of effective depth of field is valuable with all other setting being equal (ISO, flash power, shutter speed, lens angle of view, and composition).

David

[picman]

I don't get this. I have been using large aperture Zeiss lenses on my Contax system for years with great results. Why all of a sudden is the CZ 24-70, which apparently was made for full frame no longer so useful? Reduced depth of field can be very artistic, and if you want more depth of field you stop down. So what is the problem?

A good example is that I attended some photographic awards yesterday. To get photos of the presentations, it was necessary to work at f5.6 and ISO 400 with flash. When you have two or three people in a small group, not all lined up in a straight row, you need enough depth of field for the faces to all be sharp. I took the A700, not the A900, because for the same crop/angle of view, f5.6 and the shorter focal length involved is as good as using f9.5 on the A900 - and flash photos at 400 on the A700 look fine, they are not so wonderful at ISO 1000 on the A900. Reduced depth if field can be very artistic as you say, but it can also render a commercially shot image unsatisfactory for the intended use.

There is no 'problem', it's just there are different solutions to get the required results - one of those solutions is to use APS-C for certain types of photography where an extra 1.5 stops of effective depth of field is valuable with all other setting being equal (ISO, flash power, shutter speed, lens angle of view, and composition).

David

I see what you mean. For a moment there I was thinking that you were implying that the depth of field on a digital full frame was less - or seemed less - than e.g. on a film 24-36 camera given the exact same lenses.

There is something else that puzzles me. Isn't depth of field entirely determined by the lens and its f-stop? If you put the same lens on the 700 and on the 900, shoot in exactly the same direction from exactly the same spot and afterwards crop the 900 picture to get the frame of the 700 picture, you get exactly the same picture with exactly the same depth of field, or am I wrong?

Cheers, Bob.

[braeside]

There is something else that puzzles me. Isn't depth of field entirely determined by the lens and its f-stop? If you put the same lens on the 700 and on the 900, shoot in exactly the same direction from exactly the same spot and afterwards crop the 900 picture to get the frame of the 700 picture, you get exactly the same picture with exactly the same depth of field, or am I wrong?

Cheers, Bob.

You are correct, however if you were to zoom in on the A900 to get the same coverage as you got with the A700 from the same spot, then you will get less depth of field, I think that is the point that David is making.

[picman]

There is something else that puzzles me. Isn't depth of field entirely determined by the lens and its f-stop? If you put the same lens on the 700 and on the 900, shoot in exactly the same direction from exactly the same spot and afterwards crop the 900 picture to get the frame of the 700 picture, you get exactly the same picture with exactly the same depth of field, or am I wrong?

Cheers, Bob.

You are correct, however if you were to zoom in on the A900 to get the same coverage as you got with the A700 from the same spot, then you will get less depth of field, I think that is the point that David is making.

Right, that clarifies things completely. Thanks, cheers, Bob.

[Vivec]

Warning - the A900 is not necessarily a step up from the A700. To get the same depth of field at the same angle of view (i.e. 28mm instead of 17mm etc) you need 1.5 stops smaller aperture. That means using ISO 200-400 instead of 100, or ISO 400-800 instead of 200. And, it means that you need to change your habits. Program setting works fine on the A700, usually there is enough depth of field. On the A900, Program generally uses too wide an aperture. So does flash, where you have no choice over aperture unless you boost the ISO. I love the A900 but I am not blind to the reasons why it is NOT the right solution for everyday shooting!

Hi all, this is my first post here although I have been visiting this site and forum a lot -- thanks David for all your excellent articles and advice!

However, I somewhat disagree with your above statement. Basically, the a900 is just like an a700 with a bigger sensor and similar sensor technology and pixel density. Therefore, the a900 is a strict superset of the a700 and always "better" (except for price and popup flash).

One could say, that to get the same depth of field at the same angle of view as an a700 one can *either* use a 1.5 stop smaller aperture (with a higher focal length and higher ISO), *or* crop the image from the a900 (and use the same ISO, aperture and focal length). Admittedly, framing as you are using a crop sensor is less convient than using an a700 in first place

(And because it is my first post, I'll add a recent grizzly picture I made with my a700 in Canada:

[Vivec]

I agree with your points -- the a700 has indeed some sweet advantages
- price
- popup flash as controller (I use this all the time when doing realestate shoots)
- uses the sweet spot of FF lenses

but the increased DOF is only semi-true since you can always crop the image of the a900 (but of course, why would you buy an a900 in that case )

Sometimes people argue that you get more crop capability on the a900 but in practice I only seem to crop on images that I already took with my longest lens (ie. when I couldn't get any closer in practice), and in that case the a900 does not help.

The big consideration is therefore in how far the image quality in prints of the a900 would be better compared to the a700. At this point in time I have not seen any on-screen image that could not have been taken with an a700 just as well. In print, I can make excellent prints at 8x10"; since I hardly print any larger, I wonder often if the 24 MP of the a900 would give an even crisper or more detailed print at that size than the a700. Any opinons?

[KevinBarrett]

I'd just like to say "welcome" to Vivec! Going to post any pictures of the cliffracers in your neck of the woods? I'm assuming your avatar is an Elder Scrolls reference. Also, to Sonolta, well said.

[caporip]

Sonolta said

"BTW, the a700 popup flash is also a wireless flash controller, and this is a major built in feature that many a700 shooters live and swear by, it will indeed be missed by many on the 900."

You've hit the nail on the head there it is wierd not having that to rely on. I am dissapointed that the new 58 flash is limited to remotely controlling one 56 flash but i spose you can't have everything........

[David Kilpatrick]

However, I somewhat disagree with your above statement. Basically, the a900 is just like an a700 with a bigger sensor and similar sensor technology and pixel density. Therefore, the a900 is a strict superset of the a700 and always "better" (except for price and popup flash).

The A900 is actually a little lower in resolution than the A700, it's midway between the A200 and A700 at 11 megapixels. Although you can just turn on the crop mode permanently, and use it as a 1.5X camera with exactly the same angle of view/aperture/depth of field results as the A700, it lacks the greyed-out viewfinder surround which the D3/D700 offers and the crop-frame corner markings are very fine so as not to interfere with your normal viewing. It is possible to compose with them, but not in an action/fast thinking situation.

Of course, the really big difference is with wider angle views. You can get a depth of field with the 11-18mm at 11mm and an optimum aperture like f9, on the A700, which is greater than you get with the 17-35mm at 17mm and an 'optimum' setting on the A900 (I'd say that f11 is probably a reasonable optimum in this case). What makes the A900 work for me is that the 17-35mm seems much less prone to diffraction sharpness loss when you stop down to the f16 or f22 needed for many deep foreground-background views.

The Nikon 12 megapixel format is even more tolerant of small apertures due to the very large pixels, but in practice I'm still getting more detail from the A900.

Have you checked my full size pBase gallery images? They are very large to view or download, and you can also find some Alpha 700 pix too, and Nikon etc - www.pbase.com/davidkilpatrick. Nothing I have used so far matches the enlargement potential of the A900 images, as expected. You probably don't see much difference at 8x10" and there is little point in the A900 except for better shallow depth of field effects, for that size print or screen viewing. But at 16x20" size, you do see a difference and it is for this 'salon size' print the A900 comes into its own.

David