Kenko makes an extension tube set for the Sony/Minolta Alpha mount

They must be relativly new. After you mentioned Kenko I did a google search and found them. They are a bit expencive but then they do have all eight electrical contacts.

Thanks for pointing them out to me.

Dave

I just placed my order for a set of "Alpha" extension tubes, with eight electrical contacts from a place in Europe for $228.32 including shipping and a value added tax. The best price I could find in the USA was $269.00. I was told to expect deliver in five days. This is the first time I have ordered anything on the Internet from outside the USA. This will be an interesting experiment. I guess this is what the camera retailers refer to as the "gray market".

Dave

B&H has them for $169 with free shipping...

http://www.bhphotovideo.com/c/product/406965-REG/Kenko_AEXTUBEDGM_Auto_E...

Thanks but it's too late for me. I have already placed my order and paid $100 more then I had to. I should have spent more time shopping. Oh, well.

Dave

Not to add salt to the wound....but...

If you are looking at hiking IMO a better solution would be ...another lens. I'm assuming looking at your signature that the 75-300 would be your lens used most often for hiking? if this is the Sony/Minolta version it has a 1:4 (about minimum 6 feet focusing @300mm) magnification factor... I also have this lens and instead of extension tubes, I bought the new Tamron 70-300 DI lens. The price new for this lens is $159 from B&H which is cheaper than the extension tubes. This lens has a 1:2 (about 3 feet minimum at 300mm) magnification and has a focus limiter when not doing close up work. It is also optically superior to the Sony/Minolta 75-300 in every way. Carl can attest to that... It is my favorite play lens. It does not have the sharpness or 1:1 of the 100mm macro or the Tamron 90 macro that I have but the extension tubes aren't going to get you there either. It's a great all-in-one cost-effective close-up and distance lens. My Minolta 75-300 is collecting dust.

http://www.bhphotovideo.com/c/product/423729-REG/Tamron_AF017M700_70_300...

Older Sigma 70-300 and 75-250 lenses were shipped with a matched screw on close up lens. This was labelled Sigma Apochromatic Macro Lens. It happens to fit the new 70-300 APO DG lens and gives even closer focusing. They can still be found. I have a brand new old stock item bought recently from Jacobs,

Your Tamron 70-300mm lens sounds like a great lens. Do you know if it's full frame? When I shop for lenses I keep one eye on thier long term use. I have no idea if APS-C or FF will be the wave of the future. I take some comfort in knowing my "Sony" 37-300mm will work with both formats. Like you, I seldom use it. On a hike, I tend to grab my light weight 18-70mm and my 500mm f8 (not so light) and leave the rest home. If I see a panoramic scene where I might want my wide angle lens, I turn my trecking pole into a monopod and shoot multiple overlaping photos and stitch them together when I get home. I'm courious to learn how well my 500MM mirror lens will work with my extension tubes. I don't think the f8 will be a bad limitation. My theory is if you are close enough to need a macro/extention tube, you are close enough to hold a remote flash over the subject and get all the light you need, as long as you can see to focus.

Dave

It's been years since I looked into this subject. As I recall, a close up lens introduces some geometric distrortion. This may not matter much if you are looking at a bug in flower and never notice the distortion. More glass means less quality in the image. The close up lens must be able to screw into the threads of the lens you are attaching it to. Extension tubes do not introduce distortion and work with all lenses. Thoreticaly there will besome light loss but not very much and the TTL metering takes care of that.

I have used extension tubes with great success in the past with my old Konica film cameras. The depth of field becomes very limited, but that's always the case when you go macro.

I'm sure both work.

Dave

Dave: I have many of the same lenses you do, though they're the KM versions - 11-18mm, 18-70mm, 75-300mm, 500mm, and the 50mm f/2.8 Macro rather than the 100mm. And I have the Kenko extension tubes, a reversing ring, and some auxiliary close-up lenses. I've also done a lot of bellows work in the past, so overall I have some pretty good experience working up close.

Experiments with my KM 5D have yielded some surprises in that area, though. Some strange things can occur with the extension tubes. You mentioned the 500mm in particular. I find it very difficult to get the sharpness I expect from that lens at close focusing distances, especially using the tubes. And since there's no stopping down, there's not a lot that can be done about it. On the other hand, the auxiliary lenses work surprisingly well on several focal lengths. This is probably a side benefit of the crop factor, because the image is using only the 'best' central area of the lenses. I intend to eventually put together an article about some of my findings for inclusion on my site.

Anyway, if you have specific questions about any of this stuff, fire away.

Yes, the Tamron 70-300 DI is FF (full frame).

...and I haven't had any issues uses the diopters...I was really suprised especially given the price. I got a +5 for my 50mm prime (49mm) for $10. ...but I haven't taken any pictures on a flat plane... Here is a sample...

I got my extension tubes yesterday and played around with my old Kalimar 500mmf8 lens,I used just the small tube (12mm) and I took this.Its alot better than I expected from this lens.

Edit: I then used a Questar (40x80 eyepiece) telescope and got this,Im new to Astrophotograpy but Im sure I can get some nicer shots in the future.
Should I be resizing the photos smaller for this board?

Extension tubes are for working at closer than normal distances. In this case, the image of the moon using the 500mm with a tube is exactly the same as you would get with no tube. Try it both ways and you'll see.

EDIT: Or so I thought! I just tried it with one of my own mirror lenses - and was very surprised to see a slight (about 10%) increase in magnification, even with objects near infinity. Definitely not what I was expecting, but it's there.

Like you, I thought that an extention tube is the last thing you want to use to take a picture of the moon. If you say it helped I belive you but I do not understand it.
Dave

To whip out the 200-500 Tamron and the 1.4x Teleconvertor on the A350 tonight. See if I can get an even closer up shot than I did last time I tried without the 1.4x.:)

Carl

I suspect this trick will work only with a handul of mirror lenses, and only with short tubes.

First, the lens must be able to focus well past infinity on its own, which all mirror lenses can do. For this test I used a 12mm extension tube with an inexpensive Vivitar 500mm f/8 lens. I also have a Minolta AF 500mm f/8; but it can't focus beyond about 100 feet with the tube attached.

I suspect there's something about the folded light path in mirror lenses that causes the magnification effect. I've posted this question elsewhere to see if anyone can shed some light on the mystery.

Sybersitizen,

Assuming your theory is right, and I have not doubt it is from the above postings. This means that simply by adding a small extension tube between a mirror lens and the camera body, we can substantially extend the reach (focal length) of the lens without much light loss and the image degradation associated with converters with lenses in them! I have got to try this out with the Sony 500 mm f8 mirror lens and see what happens. Within the next few days I'll be hiking back out to an Eagles nest with my tripod, mirror lens, and extension tubes. I'll report back. This sounds too good to be true and you know what that means.

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Edit

I just tried it, shooting out my window at a bright yellow fire plug about 120 feet from the camera. First I took a photo without an extension tube. Then I attempted a photo with the smallest size extension tube (12mm). I was unable to focus. End of experiment. It does not work with my Sony 500mm f8 lens.

Maybe it works for other lenses, but I suspect you are seeing hollow magnification, bigger but blurry.

Dave

(First, as I mentioned in my earlier post, I too discovererd that the Minolta/Sony 500mm AF will not focus past about 100 feet with a 12mm tube attached. Still, the idea I describe here can be tested and observed with that lens - just not at infinity.)

It turns out that most photographic mirror lenses focus by changing the distance between the primary (large rear) mirror and the secondary (small front) mirror; and this is apparently true of both my lenses. The interesting thing is that changing that distance also changes the effective focal length of the lens. So with my Vivitar lens, what happens is...

1. The focal length of the lens is 500mm when it's focused at infinity.
2. The focal length of the lens increases when it's focused past infinity.
3. The focal length of the lens decreases when it's focused at closer distances.

By focusing the lens far past the infinity mark, I have changed its focal length to something around 550mm; however, I can't focus on anything that way. But adding the 12mm extension tube happens to compensate for the 'misfocusing' beyond infinity and brings objects at infinity back into correct focus. The result is that objects at infinity look 10% larger than they would under normal circumstances.

The concept can also be tested with the Minolta/Sony 500mm, or any other mirror lens. Mount the lens on a tripod and visually focus on something maybe 30 feet or so away with no tube attached. Take a shot and note exactly where the distance focusing mark is.

Now mount the 12mm tube and visually re-focus on the same subject. Take that shot and again note exactly there the distance focusing mark is. The focusing mark should be pointing to a farther distance than it was in the first shot.

The shot taken with the tube should show slightly more magnification than the one without the tube. Why? Because the lens itself was set to a farther distance, which provided a longer effective focal length.