Macro focus problem.

GlasgowGunner

GlasgowGunner

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Kevin
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HI all i am trying some macro with a Sigma 70mm 2.8 lens. The thing is when i focus on a subject only a very small part seems to be in focus and everything round about it seems to have a white cloud look round it.

Any idea's????
 
If you're shooting wide-open, it's probably just the limited depth of field you'll get while doing macro? Sorry if I've misunderstood and am insulting you! Stop down to f/11 and see if it helps!

Chris
 
I thought of that after i formated my sd card(doh).
Ok, about the F11 what is the point of the F2.8 then?

This could be the problem but i thought i would be better of at 2.8.
 
Well at f/2.8 more light will be let in, but at the expense of depth of field. In everyday situations (portraits, sports etc) the bigger aperture (smaller f-number) is great, as it can separate the subject from the background. At macro levels though, f/2.8 gives such a small depth of field that you'll be hard pressed to get the whole of the subject in focus.

Reducing the aperture to something like f/11 will increase the amount of your subject that's in focus, but reduce the amount of light hitting the sensor. For this reason, to get properly exposed, and well-focused macro shots, a flash is pretty important, or it'll be under-exposed. If you take a few more shots demonstrating the problem then someone will be able to confirm if this is the case!

Chris

Edit: Again, sorry if I'm speaking down to you, I've only just started understanding all of these things and I'm just writing down my thought process!
 
chris321 said:
Well at f/2.8 more light will be let in, but at the expense of depth of field. In everyday situations (portraits, sports etc) the bigger aperture (smaller f-number) is great, as it can separate the subject from the background. At macro levels though, f/2.8 gives such a small depth of field that you'll be hard pressed to get the whole of the subject in focus.

Reducing the aperture to something like f/11 will increase the amount of your subject that's in focus, but reduce the amount of light hitting the sensor. For this reason, to get properly exposed, and well-focused macro shots, a flash is pretty important, or it'll be under-exposed. If you take a few more shots demonstrating the problem then someone will be able to confirm if this is the case!

Chris

Edit: Again, sorry if I'm speaking down to you, I've only just started understanding all of these things and I'm just writing down my thought process!
Click to expand...

Trust me your not speaking down im a bit of a dumb a*s when it comes to all this kind of stuff.
I will try the F11 later and see what happens. The other thing is on the barrel i have macro marks(i would call them) going all the way to 1.1(which i gather is true macro) but do i have to extend my lens out this far to get the true 1.1.

I see a lot of shots on here of spiders and the likes but i cant seem to get them this size in my shots.


Thanks, Kev
 
Kev,

Not sure what lens you are using, but the principle is the same for them all. I didn't realise how to use mine until about 6 months after I got it and someone explained it to me!! I kept looking at other peoples shots and wondered why mine would never come out as well.

Here's my learnings!!

1) Set the scale to 1:1 on the lens barrel
2) Take off AF, you must use manual focus for macro
3) Get the focus purely by moving the camera - don't change the lens or try to focus with it. If you do, all you'll do is change the 1:1 ratio and not end up with macro.
4) Try it at f11 - This will give you a more workable DoF, although it's never that great to be honest.

Hope that helps - I certainly wish I'd known this when I started with my macro lens. I felt a total prat when I realised how I should have been using it!!
 
Kev,

A quick course in macro shooting......

The "depth of field" is the term used to describe what parts of the image will be acceptably sharp or in focus....usually abbreviated to DOF.

DOF is a function of magnification and aperture...larger magnification or/and larger aperture result in smaller DOF. Focussing closely results in greater magnification and this is how most macro lenses achieve the high magnifications...they simply allow you to focus more closely.

So, when you frame your subject (a fly for example) then you will be working close to 1:1...ie, the fly will be projected onto your sensor at or close to life size.
This high magnification results in a very shallow (small) DOF and the only way to increase it is to use a smaller aperture....typically f/11 to f/16.
If you were to shoot a larger subject (a butterfly for example) then you would be further away and using less magnification (maybe 1:4) to project the image onto your sensor. This lower magnification increases the DOF and gives you some possibility to use a larger aperture (f/4 to f/8) and still keep the whole of the subject in focus.

Why have an f/2.8 lens for macro then you're asking? The lens is wide open until you take the shot. If the lens was only f/8 then focussing would be difficult due to the very dark viewfinder at the smaller aperture.

Focussing is normally achieved by adjust the focus ring to get the subject roughly in focus and framed to your liking and then moving the camera/lens slightly forwards or backwards to achieve sharp focus exactly where you want it....usually the head or eyes if you're subject is an insect or suchlike.

If your subject is two dimensional like a coin or similar then you really don't need much DOF and any aperture will do.

One final thing to beware of.....
At very small apertures, diffraction softening will occur and you're going backwards again in terms of sharpness. I would advise sticking to f/11 to f/16 until experience tells you what you can get away with on a subject by subject basis. Sometimes a shallow DOF can be beneficial as it will highlight only the portion of the subject you're interested in or simply add a little artistic flair to the shot.

Practice is everything in macro and it'll all fall into place very quickly if you analyse your shots and review them whilst referring to the EXIF data.

HTH

Bob
 
Canon Bob said:
Kev,

A quick course in macro shooting......

The "depth of field" is the term used to describe what parts of the image will be acceptably sharp or in focus....usually abbreviated to DOF.

DOF is a function of magnification and aperture...larger magnification or/and larger aperture result in smaller DOF. Focussing closely results in greater magnification and this is how most macro lenses achieve the high magnifications...they simply allow you to focus more closely.

So, when you frame your subject (a fly for example) then you will be working close to 1:1...ie, the fly will be projected onto your sensor at or close to life size.
This high magnification results in a very shallow (small) DOF and the only way to increase it is to use a smaller aperture....typically f/11 to f/16.
If you were to shoot a larger subject (a butterfly for example) then you would be further away and using less magnification (maybe 1:4) to project the image onto your sensor. This lower magnification increases the DOF and gives you some possibility to use a larger aperture (f/4 to f/8) and still keep the whole of the subject in focus.

Why have an f/2.8 lens for macro then you're asking? The lens is wide open until you take the shot. If the lens was only f/8 then focussing would be difficult due to the very dark viewfinder at the smaller aperture.

Focussing is normally achieved by adjust the focus ring to get the subject roughly in focus and framed to your liking and then moving the camera/lens slightly forwards or backwards to achieve sharp focus exactly where you want it....usually the head or eyes if you're subject is an insect or suchlike.

If your subject is two dimensional like a coin or similar then you really don't need much DOF and any aperture will do.

One final thing to beware of.....
At very small apertures, diffraction softening will occur and you're going backwards again in terms of sharpness. I would advise sticking to f/11 to f/16 until experience tells you what you can get away with on a subject by subject basis. Sometimes a shallow DOF can be beneficial as it will highlight only the portion of the subject you're interested in or simply add a little artistic flair to the shot.

Practice is everything in macro and it'll all fall into place very quickly if you analyse your shots and review them whilst referring to the EXIF data.

HTH

Bob
Click to expand...


Gosh that was handy, Thanks.

And yes the F11 was spot on so great advice from all who replyed, Now off to find a spider.lol
 
Bob, that post of yours should be a sticky in the macro section :)
 
My sigma 105 should arrive tomorrow. So much of the foregoing is going to be such a help. Thanks guys:)

Brian
 
Well it has arrived. My question is am i having a senior moment?:) Have put the lens on my D60, sussed out a few things, but there is one that i cant get my head round.

I get "lock lens aperture ring at minimum aperture(largest f-number)" message on the camera. It seems to me that it is only possible to lock the aperture ring at 32(in red), it wont lock at 11 for instance. Totally confused now

Brian
 
fernface said:
Well it has arrived. My question is am i having a senior moment?:) Have put the lens on my D60, sussed out a few things, but there is one that i cant get my head round.

I get "lock lens aperture ring at minimum aperture(largest f-number)" message on the camera. It seems to me that it is only possible to lock the aperture ring at 32(in red), it wont lock at 11 for instance. Totally confused now

Brian
Click to expand...

yes you're right, you can only lock the aperture ring at the minimum aperture, f/32 in this case. you need to do this, and then you can control the aperture used to take an exposure with the camera, not the aperture ring. this is how modern Nikon cameras handle lenses with aperture rings. if you look at a Nikkor AF-G lens, you'll see they don't even have an aperture ring. Hope this helps.
 
Spudgun said:
yes you're right, you can only lock the aperture ring at the minimum aperture, f/32 in this case. you need to do this, and then you can control the aperture used to take an exposure with the camera, not the aperture ring. this is how modern Nikon cameras handle lenses with aperture rings. if you look at a Nikkor AF-G lens, you'll see they don't even have an aperture ring. Hope this helps.
Click to expand...


Thanks very much for that. That was the conclusion i had reached. Sets my mind at rest, thought it was broke!!!. What a good site this is, perfect for a senior prat like me:lol:

thanks again Brian
 
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