problems with D90

[Roadrunner]

Hi,

just got my new toy a D90. Hooked up my old Sigma 20-70 2.8 and started shooting. First thing I've seen is that a lot of the shots seem to be out of focus and some have a white/grey layer like fog.

Even if I shoot at f22 the depth of focus id not that much. Did a birthday photo and candles are sharp but the little girl 30cm behind is not.
Did this shot of the bus today and the big version is very unsharp the focus points are the front of the bus and f20 1/100s. The bus is not really sharp and with f20 everything a few meters in front and behind the bus is very unsharp.
I can't recall that this happened when the Sigma was setup with my old 801s.
https://www.aulro.com/afvb/images/imported/2010/01/426.jpg

Matt

[dullbird]

have you looked at your focal points in the camera?? you can set them up to centre or off centre I think my camera has something like 8 differing spots I can set focal point too.... might be worth checking..

The only other thing I can think of is your lense and contacts may be dirty

[dmdigital]

I've heard of similar issues with older model Sigma 150 f/2.8 Macro that they won't focus lock. The solution was a firmware upgrade (or it might have been a rechip) by Sigma.

I suspect this may be what you are encountering.

[Roadrunner]

It shows the focal points when you take the picture. They have been on th front corner of the bus.

1/60s f8 and only the front of the cherry is sharp although it was tasty.
https://www.aulro.com/afvb/images/imported/2010/01/424.jpg

1/200s f11 one of the first shots. f11 and really only the center is sharp.
https://www.aulro.com/afvb/images/imported/2010/01/425.jpg

[Roadrunner]

another one. 1/640 f4
focus point was next to the ear. Not even the nose is sharp and the whiskers blur somehow.

https://www.aulro.com/afvb/images/imported/2010/01/423.jpg

[dmdigital]

OK, misunderstood. The lens has an aperture ring if it's the same as the Nikkor "D" lenses then it should be set to the highest f-stop (22) and if possible locked in position. Although the camera should give an Error if the lens' aperture isn't in auto mode.

[Roadrunner]

I've done that. Set to f22 and I shoot in A mode most of the time. The thing I don't get is that it seems I only get a few cm in depht that are sharp.
Take this one.
1/200s F18 focus point is nose of the kid. The kid behind her is maybe 30cm behind her and not sharp at all and that's with F18.
https://www.aulro.com/afvb/images/imported/2010/01/420.jpg

[dullbird]

do you have any other lenses you can try?

[dmdigital]

Just looking at the EXIF data and it knows the lens, aperture (F/18), focal length used etc. All looks good, except the image. It's like the lens isn't closing down the aperture blades correctly. Have you tried using the DOF preview on each f-stop and see what the lens does?

[Roadrunner]

Any suggestions on a lens in the $500 range ?
Maybe 18-50 or 70

Matt

[Roadrunner]

Also have a Soligor 70-210 2.8-4
F22 and background not sharp.
https://www.aulro.com/afvb/images/imported/2010/01/365.jpg

[dmdigital]

Given up Matt or have you confirmed the aperture is not actually working as per what it's telling you?

Not much around $500. The 18-50 is a kit lens, very plasticy.

[Roadrunner]

I just don't understand it. If I choose f22 shouldn't that give me the max focus depth ? So in my past shots with 2 different lenses and f22 objects 30cm behind the focus object are not sharp. Does that make sense ?

Thanks for your help.

Matt

[dmdigital]

It depends on the hyperfocal distance.

Also I just realised something, this is a DX camera and so you are effectively shooting f/16 when at f/22 from the point of view of hyperfocal distance. This is because the you are effectively looking at a smaller circle of confusion or in simple terms a magnified image (remember the 1.5x crop factor of DX).

Am I making sense?

[Roadrunner]

Might be making sense but you're pushing my limits :)

So what is a good lense for the D90 ? The whole point was that I could use my old lenses.
Just seen this one Tamron 17-50mm f/2.8 XR Di II Lens is around $700 imported. I think 17-70 would be good as it covers a lot.

Matt

[dmdigital]

OK, glad I didn't just add to the confusion.

The Tamron lens is a Di which means it is designed for the DX size sensor, just like the DX lenses from Nikon.

Basically any lens designed for digital cameras is going to be OK, some will be better lenses than others. A lot has to do with the ability to focus the light straight to the sensor which was something that wasn't as important on film. This is to do with the photosites on the sensor and the microlens technology employed to direct the light on to them.

[Bushie]

Plug some figures into this and see what it gives you, as a comparison

Depth of field calculator (http://www.dofmaster.com/dofjs.html)


Martyn

[miky]

Might be making sense but you're pushing my limits :)

So what is a good lense for the D90 ? The whole point was that I could use my old lenses.
Just seen this one Tamron 17-50mm f/2.8 XR Di II Lens is around $700 imported. I think 17-70 would be good as it covers a lot.

Matt

It's the old story Roadrunner - it depends.

I find the 18 - 200 (http://www.digitalcamerawarehouse.com.au/prod6290.htm) a good all round lens.
Edit: Disclaimer - The page is just to show the lens. Not advertising the company.

Mike

[Roadrunner]

So when I type in 52mm f22 also I will only get f16 with f22 :) and distance 1.5m I get total depth 77cm :eek:

So how do you take a picture where the person in the front is sharp and everything behind that person ?? f64 will give me 3.8m

When I take my little point and shoot Canon and have F8 everything gets focused.

Matt

[Taz]

So when I type in 52mm f22 also I will only get f16 with f22 :) and distance 1.5m I get total depth 77cm :eek:

There maybe some confusion here. Smaller sensors have greater depth of field for the same aperture. So if we take a 'full frame' (ie 35mm) sensor as the reference, your APS-C sized sensor (1.5 or 1.6 crop factor) will have greater depth of field at the same aperture. So, in order to match F16 on your camera, a full frame camera would need F22 to achieve the same depth of field (everything else being equal).


So how do you take a picture where the person in the front is sharp and everything behind that person ?? f64 will give me 3.8m

Get a wide angle lens or stand further away with your existing lens on its smallest aperture setting (F22) and use hyperfocal focus. For example, I know that I can get everything tack sharp from 2-3ft to infinity using my 24mm lens set to F22 on my 35mm camera.

I think you may be expecting a little too much from F22 on your camera with the apparent close range of some of your shots.



When I take my little point and shoot Canon and have F8 everything gets focused.

These point-n-shoots have tiny sensors. Tiny sensors = huge depth of field. Hence the reason why you dont see focusing on mobile phone cameras - they dont need it :)

Perhaps if I can also add... when it comes to portraits, the ones I like the best are the ones where the subject is seperated from their background using very short depths of field.

[Taz]

Basically any lens designed for digital cameras is going to be OK, some will be better lenses than others. A lot has to do with the ability to focus the light straight to the sensor which was something that wasn't as important on film. This is to do with the photosites on the sensor and the microlens technology employed to direct the light on to them.

These are called telecentric lenses. Because the surface of a digital camera sensor is shiny, they reflect a lot of light, particularly light that strikes the surface of the sensor from off axis (not perpendicular to the surface). This is also the reason why lenses designed for digital cameras have anti-reflection coatings on the rear element; this tries to stop light reflecting off the sensor, then hitting the rear element, then reflecting back onto the sensor etc etc, generating a kind of ghosting effect. This is not so much of an issue with film as film does not reflect as much light and can absorb it evenly from off axis directions.

[dmdigital]

Thanks Taz, my explanations were loosing something and need someone else's input. I'd forgotten about the reflection issue.

[Roadrunner]

Thanks Taz. So it looks like the lens is doing what it should do and that "F" settings are not the same on different cameras. I was under the impression that f22 should make everything sharp from front to back. Seems like a lot to do with sensor size.
So If I get a new lens I might have the benefit of the anti reflection coat on the glass. I agree that it looks nice if the background looks blure but I was testing a few things and thought f22 will give me heaps of depth. And it seems to be very extreme that sometimes the nose is sharp and the ears are not. Will be a good thing if you can control it although you do not always get f16 or f22 depending on light.

Looks like I need another few thousand test shots ;)

Matt