http://www.bythom.com/nikon.htm

Thanks for the info

yes. a bit on the skin

Here:

http://www.photomalaysia.com/forums/showpo...&postcount=1379

But when obtaining similar field of view, 50mm on DX versus 85mm on FF.

Let's say 85mm stands 1 meter away from focus point, the 50mm would be roughly 1 meter away too right? The dof for 85m would be more shallow isn't it due to focal length.

Not necessary, for instance,

85mm f1.4 on full frame body and you are 1 metre away from the subject.
50mm f1.4 on cropped body and you are 1 metre away from the subject.

If you ignore the minor differences, you should be able to get the same field of view, but when both steps closer by half a metre

85mm f1.4 on full frame body and you are 0.5 metre away from the subject (you get OOF shot due to you went beyond the MFD)
50mm f1.4 on cropped body and you are 0.5 metre away from the subject. (you get a narrower DOF due to the nearer the subject's distance to you, the narrower the DOF except you go beyond the MFD)

Understood, but I was comparing when both lens are still within focus distance. If beyond MFD no point comparing since can't even get a lock on the focus already.

I think to help identify the problem of the picture, it doesnm't really matter if his picture have more shallow DOF than yours or vice versa. The key point here is, there is shallow DOF. For the picture that I see, I would say the DOF is shallow since its considered close up, and we're also nolt sure if he uses focus recompose technique, if yes, this further cause the problem.
Even if he did not focus and recompose, it can be he focus and lock and during framing and waiting for the moment, he move or the subject moved shifting the focus plane.
As I said, there can be many reasons, only the person knows best. From the picture, what I can say is there is shallow DOF since its close up, the rest, it depends on the technique and how the shot was taken.

No point comparing both within same distance cause everyone knows obviously the 85mm f1.4 on full frame has a shallower DOF compared to 50mm f1.4 on cropped sensor body.

The reason I highlighted that MFD does affect too cause Andy214 was saying that the picture above appeared to be taken very close, so high chances the shooter went very close to the subject considering 50mm f1.4's MFD is 0.45metre allowing the shooter to go very very close.

I see that we are tuning the same channel

I think the subject moving around, shifting the focus plane may sound reasonable, especially when you are indirectly shooting her, and she will just move her face to other photogs on and off.

This post has been edited by geekster129: Apr 25 2011, 12:26 PM

Yes and it's one of the common factor that causes you to get OOF shots

That's why proper communication is important. Sometimes, I will confirm my focus lock few times when the model looked at me. Tit tit tit few times if I got the time luxury, this will sometimes guarantee really tack sharp focus, even on my kitlens.

Some inexperienced model will move their body a tad when they pose without knowing this is bad for the photogs who just locked their focus.

PC Fair I would care less. OOF shots will go straight to the recycle bin.

But for outdoor portrait shooting where I can talk to my models, and if I want to achieve certain shots, I would tell her, "OK, look at me, I focus on your eyes... but don't move". If she moves, then I have to educate/coach her not to move much. So sometimes, it requires a few takes before I got that perfect shot with perfect focus especially if it's a complicated pose which involves movement and dynamics. It worth the effort.

This post has been edited by geekster129: Apr 25 2011, 12:39 PM

Hence effective communication is one of the key!

i dunno about the rest (comparing close up focus and 50mm vs 85mm lens)
but i thought this photo was one of those accidentally click on the camera type of photo.
terus masuk recycle bin.

if i focus on the subject's eye and then recompose the picture. the focus point will be different already?
I am asking this because, when i use my d7000 focus on any subject and then recompose it, my focus point will be at middle( I turned on "show focus point" from the menu of d7k). Btw, i am using centered weighted metering

Think in a 3D space. If you subject distance to you is the same, then F&R method still OK. If you have focused and then the subject moved to the back or front, then the area you want to focus is out of the focal plane and you get OOF.

About centered weighted metering, well, it has nothing to do with autofocus. It is for the automatic exposure calculation by your camera when you use A,S, and P modes to estimate the proper shutter speed, aperture and ISO in order to get a proper exposure.

Autofocus for Nikon usually got 3 modes: AF-S, AF-C, and AF-A

This post has been edited by geekster129: Apr 25 2011, 02:57 PM

i know about this. but i am not asking this.

when u press the preview button on the d7k. u can actually view your photo and display where is your focus point. but my problem is, the focus point on the photo always remain on the middle

You mean you can't change the AF point?