GH2 New to replaceable lenses

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Decius

Active member
So I've got the tamron 35-80mm lens attached to the camera with an adapter, and it looks beautiful.

However, I'm very not well versed in lens focusing at all so I need a quick lightning lesson. One thing that's bugging me is I took the camera out on my balcony and was trying to get sort of a panoramic shot of the city and I could not get it to focus on cars far off in the distance. I thought I would be able to, but I was only able to when i really reduced the aperture.

Can someone explain to me the relationship between being able to focus on a subject, whether the zoom lens is wider or more telephoto, and how aperture relates to it?

Thanks.
 
Sounds like your infinity focus is not set correct. Usually this is due to an adapter not being made to tolerance. I have a few Canons that won't focus to infinity, but others that will on the same adapter.
 
I don't know what that means... what's an infinity focus? What does the adapter have to do with it?
 
Decius said:
I don't know what that means... what's an infinity focus? What does the adapter have to do with it?
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The lens optics are designed to focus at certain points given the distances from the 'object' in focus to the lens and the distance of the lens to the sensor plane. If the adaptor is not built with the correct distance, focus will be affected. 'Infinity focus' is what you are trying to 'get' by focusing on distant objects, and means that the lens is slightly further away from the sensor plane than lens was designed for.

This could mean, 1) you have a defective or not correctly designed adapter, 2) the lens that you are using 'can't' be focused at infinity because the adapter+Lumix body don't allow the lens to be close enough to the sensor.

It may be that you can only use the lens stopped down to get the DoF 'working' for you.

Since you are using a Tamaron lens, and Tameron makes lenses for a variety of cameras, you need to make sure the lens and adapter match, as well as that particular tameron lens and the resulting adapter have 'infinity focus' capability.

I only have Nikon lenses so all I had to do was find an adapter that had infinity focus for Nikons. As it is, I've only used it a couple of times with a 200mm Nikon lens I have.
 
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Decius said:
Ah, okay.

Well I am using this adapter:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250738969620&ssPageName=STRK:MEWNX:IT

And it says it supports infinity focus. Is it possible it still doesn't with the GH2?

Also, why does it appear more focused when the aperture is reduced?
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Depth of Field is 'symetric', that is there is a DoF centered on the object in the distance, and there is a DoF on the formed image plane at the sensor.

You can actually 'see' this, especially if you are near sighted, take a small 'pin hole', hold it to your eye, and eh wala... the image you see is 'sharper'... I've seen a pair of 'sunglasses' with holes drilled in the lenses, and for simply myopia, the effect is that things appear sharper... doesn't help for astigmatism... alternatively build a pinhole camera and watch the neighbors on your livingroom wall... ok, during the day, and your livingroom curtains completely closed except for a small 'pinhole' to allow the light from the outside to be projected onto the far wall.

This is why shooting 'wide open' really needs to be evaluated, and done only if it is absolutely necessary. Stopping down covers a number of wyrdnesses with lenses, and various adjustments or lacks thereof.
 
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Ah, thanks makes sense.

As for the adapter I mentioned, is it possible it does not work with infinity focus even though they specify that it does, and even mention the GH2?

Or is there the possibility that when the aperture is wide open, even with infinity focus, things in the distance cannot be focused?

Because I closed the aperture to its max and still couldn't perfectly focus on things in the distance.
 
Decius said:
Ah, thanks makes sense.

As for the adapter I mentioned, is it possible it does not work with infinity focus even though they specify that it does, and even mention the GH2?

Or is there the possibility that when the aperture is wide open, even with infinity focus, things in the distance cannot be focused?

Because I closed the aperture to its max and still couldn't perfectly focus on things in the distance.
Click to expand...

At this point you'd perhaps have to have the Tameron looked at, to see if it is 'ok'. If you have the camera the Tameron was originally made for, Nikon, Canon, whatever, you could 'test'
it on that camera (or borrow one...), and see if the lens is working correctly for some camera...

There is also an optimum f-stop for lenses, usually around 2-3 stops down from wide open, as you get smaller stops, you run into another problem, defraction, which may cause a 'softening' as well.

Years ago the Wife bought a Sigma lens when she was on travel in Australia, and never was satisfied with it in terms of 'sharpness'. The Wife ended up buying a $1500 Nikon lens to give her what she needed... Eventually we 'lent' the Sigma lens to the Daughter, who lost it...
 
It seems unlikely it's the tamron, and more likely that it's the adapter, from what i've gathered. Do you think that is the case or not?
 
Anyways, for anyone interested in knowing, I figured it out.

With this lens, if you gently unscrew the front lens and a little ribbed washer, you can actually disasemble the lens. In doing so I found that the thread notch that the lens was connected on was incorrect, and after some testing I found the sweet spot where infinity is basically achieved.
 
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