Shooting with high apertures ,makes focussing hard ?

311

I have a 1.4 prime lens that I use all the time indoors. I find it almost impossible to manually focus for candids with the lens set at 1.4 because the DOF is so small.

Has anyone come across this and am I on the right track thinking the way I am.

Borderfox

I was reading a piece on autofocus and they say to put the box you set for focusing at the edge of the face to get a difference in contrast and you should get a lock. I have a 50mm f1.8 and have no problem with focus.

Zillah

Yup, tiny DOF leaves you very little margin for error with focusing. Just gotta be careful.

311

Nice one ,sometimes I try and use manual focus for portraits indoors and they come out like paste. wasn't sure if it was the lens or not.
I think i'll bang the aperture up to 2 or more and increase the ISO. Can be a headwrecker when I think the lens is faulty.

Thanks.

masteroftherealm

Yup thats the beauty of a nice fast lens.
The results wide open will be beautilful if u can priactice the manual foccusing.
Trust me.
Its a skill youll love eventually.

JMcL

_Brian_ wrote:

I have a 1.4 prime lens that I use all the time indoors. I find it almost impossible to manually focus for candids with the lens set at 1.4 because the DOF is so small.

Any reason why you don't use AF? A fast prime like that should have fast and accurate AF even in low light given that the camera focuses wide open and only stops down the lens when the shot is taken

Borderfox wrote:

I was reading a piece on autofocus and they say to put the box you set for focusing at the edge of the face to get a difference in contrast and you should get a lock. I have a 50mm f1.8 and have no problem with focus.

Hmmm, that could be a problem with a 1.4 lens, the DOF will be razor thin (using the calculator here it's +/- 4cm at a distance of 2m on a 1.6x sensor), and with portraits it's vital to have the eyes in focus. Focusing on the side of the face you'd quite possibly not have that.

John

elven

It might also be worth switching to using one AF point rather than letting the camera choose them. Then you can point it at the eyes and it probably would pick up the details there enough to focus.

It is also a consideration, to switch to MF. Sometimes it's quicker and easier. I just wish my eyes were a bit better at telling what's in focus, in the viewfinder

JMcL

elven wrote:

It might also be worth switching to using one AF point rather than letting the camera choose them. Then you can point it at the eyes and it probably would pick up the details there enough to focus.

Good point. On Canons at any rate, the centre focus point is larger and will detect focus in both horizontal and vertical planes. The other points only work in one plane.

The other thing you can do, which has just occurred to me, is to leverage the cameras AF system in manual mode. When in MF mode, and with the shutter button half depressed, the AF points light up when the camera detects focus. With a fast lens, it should work quite well in low light.

311

Thanks for the comments ,Elven I think i'll stick to what you said and use autofocus on one point.
Jmcl the focus light comes on alright in Manual focus ,but it's only on in about a 1/4 inch . So if I move either in or out slightly the focus is gone.

The 1.4 is great for stills and product shots ,the DOF is amazing .The lens is the sigma 30mm 1.4 HSM.

Cheers

Redundo

The type of camera you have also has a huge bearing on how easy it is (or isn't) to focus manually.

Modern Digital SLR's are actually the toughest camera to try and successfully focus a lens manually. This is because with the crop factors, the viewfinder is smaller and dimmer then you would expect from another camera. Also modern Digital SLR's don't exactly use the best focusing screens anyway. One trick you can do to focus manually is to rapidly rotate the focusing ring from near to infinity and watch the zone of sharp focus move in and out. But really you are best off using autofocus.

Film SLR's are easier to focus manually mostly because of a larger and brighter viewfinder, but newer Film SLRs still have crappy focusing screens. Some older model SLR's use split focusing screens, where almost like a rangefinder, you focus by lining up vertical lines. It's very quick, very accurate and a joy to use. Best of all are medium format cameras due to the even larger viewfinder, split focusing and often built-in magnifiers to really get a close look at your subject.

I would be really surprised if there was anything wrong with your lens. Really surprised. The type of camera used however can have a big effect on your ability to manually focus.

:cool:

masteroftherealm

Redundo wrote:

The type of camera you have also has a huge bearing on how easy it is (or isn't) to focus manually.

Modern Digital SLR's are actually the toughest camera to try and successfully focus a lens manually. This is because with the crop factors, the viewfinder is smaller and dimmer then you would expect from another camera. Also modern Digital SLR's don't exactly use the best focusing screens anyway. One trick you can do to focus manually is to rapidly rotate the focusing ring from near to infinity and watch the zone of sharp focus move in and out. But really you are best off using autofocus.

Film SLR's are easier to focus manually mostly because of a larger and brighter viewfinder, but newer Film SLRs still have crappy focusing screens. Some older model SLR's use split focusing screens, where almost like a rangefinder, you focus by lining up vertical lines. It's very quick, very accurate and a joy to use. Best of all are medium format cameras due to the even larger viewfinder, split focusing and often built-in magnifiers to really get a close look at your subject.

I would be really surprised if there was anything wrong with your lens. Really surprised. The type of camera used however can have a big effect on your ability to manually focus.

:cool:

Here here to that!
I love my old SLR foccusing screen. Mmm matt splitfocus.
Saw one for my old 350d never got around to getting it tho.

Dunno bout Nikon Screens yet havent had a chance to look into it.
Would be something Id definitly replace givent the chance tho.

311

thanks redundo ,I've got an old 50E I bought a while back and I love using it because of the clarity of view .
I do find myself that looking through a standard lens on a small sensor camera sometimes is pointless . It's like looking through a straw taking a shot.

It's not as much of a battle for me anymore to decide what to buy ,the 30mm 1.4 and 10-20 4-5.6 lenses are all I'll ever buy solely for the 350D.

Roen

You can install the older style split focusing screens on your new DSLR's. They cost extra of course and are probably a pain in the ass to fit, but on the plus side you only gotta do it once. Here's an example.

311

Thanks for that link roen ,I looked up a few things and I think that my camera has only third party options for this.

Heres a link I found http://www.camerahacker.com/Tools/Installing_Haoda_Screen.shtml

It doesn't look mind boggling ,but I don't have access to an area clean enough to try it ,so I think I'll leave it.

Thanks

Brian.