Help please with focus during busy picture..

[parkim]

Hi guys, im new to photography and this forum and hoping to learn lots here..

Iv linked a video which i need help on,

I dont understand how to just focus on the potato... Dont ask me why its a Potato.. Its all i had to practice on at the time of playing with my camera... Is it even possible to focus on just this?

As it was it was on AUTO and the lense was on AUTO focus also, Using a tripod... I was using my NIKON d5100 with 55-300 lens AF-S DX f/4.5-5.6G ED VR

Help would be appriciated as to which setting would be best, as you can see its all over the place at the minute.

Much appriciated..


focus potatoe - YouTube

 

[scorpion_tyr]

For something that small you'll probably have to use manual focus... wish I could help more, I know very little about DSLR video.

 

[rokvi]

+ 1 ^

 

[SCraig]

When focusing during video the autofocus module looks for variations in contrast (in reality that is how the D5100 always focuses, but I mentioned it since not all DSLR's use that method in still photography), and they will normally focus on the closest object. In this case it appears to me that the focus was varying between the potato and the blade of grass in front of it. When the breeze blew the grass away from the potato it appears that the autofocus module saw it but when it was right in front of the potato there wasn't enough contrast for it to differentiate it.

Autofocus is not a foolproof process. There are always going to be cases when it will not work properly. The key is in understanding when it will do what you want and when it won't.

I don't shoot video at all, but my recommendation would be to ALWAYS use manual focus when shooting video or you are at the mercy of the camera. It may decide to focus on something else when you don't want it to, something completely unrelated to the video. If you are using manual focus that will never happen.

 

[KmH]

I agree with Scott that auto focus has limitations and if you look at page 40 of your D5100 User's Manual you will see that Nikon states that auto focus will have difficulty with any scene that has many fine details.

Their example is very similar to the scene you were shooting.

 

[parkim]

Thanks Scott.. I have played around with the manual focus and i struggle to understand it to be honest.... If for example i was using manual focus on the object... How would i be able to zoom in the same, While still maintaining a good focus, i tried it on the day and it just went blurred as did everything else.

I am not sure if there is a setting i am missing on the camera, I switched the lens to manual and played around with the camera also,

 

[parkim]

I agree with Scott that auto focus has limitations and if you look at page 40 of your D5100 User's Manual you will see that Nikon states that auto focus will have difficulty with any scene that has many fine details.

Their example is very similar to the scene you were shooting.

Which manual is that? I have the expanded guide and i dont think it is in that one? Is there another available?

 

[SCraig]

I agree with Scott that auto focus has limitations and if you look at page 40 of your D5100 User's Manual you will see that Nikon states that auto focus will have difficulty with any scene that has many fine details.

Their example is very similar to the scene you were shooting.

Which manual is that? I have the expanded guide and i dont think it is in that one? Is there another available?

I found what he is referring to on page 49 of the D5100 User Manual at the bottom of the page.

 

[SCraig]

Thanks Scott.. I have played around with the manual focus and i struggle to understand it to be honest.... If for example i was using manual focus on the object... How would i be able to zoom in the same, While still maintaining a good focus, i tried it on the day and it just went blurred as did everything else.

I am not sure if there is a setting i am missing on the camera, I switched the lens to manual and played around with the camera also,

As I said, I don't shoot video so I can't really answer your question. It would be a function of the particular lens to maintain focus when zooming. I don't know whether that's common or uncommon since I've never had to worry about it shooting still images. All of my lenses do change focus when I zoom, I think. I've never really paid that much attention to it.