Focusing Issue....

[ErikJonas]

I was not sure what heading this went under so i chose this one.

I'm not sure if this is a issue with Nikon or other camera lines but i know its one with Pentax.

In low light situations the auto focus does not respond well.Yesterday during a shoot we went to the water front to shoot some shots with the sun setting behind her.At the water front there was a Sealion on a log that was not far from the dock.I set my tripod up but the auto focus would not lock on to anything and focus so i switched to manual focus but that as well in low light can be a challenge.

So here i had a shot of a Sealion,beautiful sunset in the back ground and i cant get my camera focused.To add insult to injury a young Sealion pup joined the adult one on the log,so cute,sunset in the back ground and I cant get a thing.There was still enough light out for a long exsposure....

I know this can be done i have seen a number of night images that are tack sharp.Are there some cameras that have a auto focus that does really well at night?Maybe film cameras focus better at night the digital ones?

 

[Bart_van_der_Wolf]

So here i had a shot of a Sealion,beautiful sunset in the back ground and i cant get my camera focused.To add insult to injury a young Sealion pup joined the adult one on the log,so cute,sunset in the back ground and I cant get a thing.There was still enough light out for a long exsposure....

I know this can be done i have seen a number of night images that are tack sharp.Are there some cameras that have a auto focus that does really well at night?Maybe film cameras focus better at night the digital ones?

The camera specs should tell what the lower threshold (in EV) for AF is for your camera. Different cameras have different boundaries, but they all become a bit slower towards the dark, till they fail to focus. Then it's time to switch to manual focusing. You can calculate the EV from your ISO, Aperture, and Shutter speed.

Cheers,
Bart

 

[ErikJonas]

????

So is there a camera known to do better for focusing in lower light conditions?One that performs better then others?....I'd be some what inclined to think the camera sensor ties in a bit to the focusing abilities....Full frame i know you can just go crazy with the ISO and get next to no noise.but what about the focusing abilities does that help at all there?

 

[Bart_van_der_Wolf]

So is there a camera known to do better for focusing in lower light conditions?One that performs better then others?....I'd be some what inclined to think the camera sensor ties in a bit to the focusing abilities....Full frame i know you can just go crazy with the ISO and get next to no noise.but what about the focusing abilities does that help at all there?

The more expensive DSLRs often do better under extreme circumstances. The PENTAX K-x has a useful AF range of 1-21.5 EV @ ISO 200. I don't know the AF specifications of your Pentax.

I'm a Canon shooter, and my EOS-1Ds Mark III is specified to allow AF between -1 EV and +18 EV (at 23 degrees C, ISO 100). So when the required exposure at the focus position is e.g. 15 seconds at f/2.8 (@ISO 100), that's on the border of what AF can do with that camera (pretty dim light, 3 stops dimmer than the above mentioned Pentax model). It is assumed that there is some structure to focus on, obviously. When the lens opening is wider than f/2.8, then that's what is used to focus with. In practice, my camera stops achieving AF at approx. 2-3 seconds at f/2.8 @ISO 100, so not quite the level as advertized ...

Cheers,
Bart

 

[Asher Kelman]

Erik,

Several tricks I use. First use the flash on your camera set to a low setting but with a assist light so it will figure the focus for you. Next the spoon trick. Have a little tea spoon and put that in the plane of the picture you want to shoot. focus on that and then recompose. Won't be perfect at the widest f stops when you are very close but generally will do well.

Combine the two methods!

Asher

 

[ErikJonas]

...........

Asher....Never in my wildest dreams did i think coming to this forum i'd be told to spoon... =P
Great idea though thanks.

Bart...I've not heard of the Pentax K-x is that new?

 

[Bart_van_der_Wolf]

Bart...I've not heard of the Pentax K-x is that new?

http://www.pentax.jp/english/news/2009/200918.html

The last Pentax I used was a film based model in the '70s. I'm not familiar with the current Pentax product line, so there may well be other models with better performance, I just used the one in the link as an example.

Cheers,
Bart

 

[ErikJonas]

....................

Bart thanks so much....I did go to that link and what caught my eye other then the red camera body was the 55-300mmF4-5.8ED lens....I have a Sigma APO 70-300 that i use now but like the idea of the 55-300 much better.

Thanks though for the help......Erik....