The Wein MRB400 cell is a zinc-air battery that is an exact equivalent that delivers the correct 1.35v

When you get one of these, peel off the sealing strip and leave it for about 30 minutes to activate, then it should be fine.

Some users put 1.5v silver oxide cells in their Spotmatics, but personally I do not think this is a good idea. The different voltage may alter the meter reading by up to 2 stops, and there is always the chance that the circuitry could be damaged by the higher voltage.

My advice is to use the correct Wein cell.

Not particularly - it does have slight movement because it is an autofocus lens and they are not as rock-solid as manual focus ones. Trouble is, it's hard to judge what you define as a "slight rocking" - how slight is slight?

If it seems excessive (another subjective assessment!) try another in a dealers to compare, but above all, does it produce sharp pictures OK?

I totally agree with Matt - a card reader is the best way to go.

Very wise!

It's a brave soul that even starts to reply to that....

When a lens is the right way round the distance to the subject is large, the distance to the film small. You get a normal sized image. Reverse the lens and you reverse that logic and end up with huge magnification. Try putting a wide angle lens in reverse on the front of a telephoto and see what happens.

By a telephoto lens adapter do you mean a teleconverter, or maybe a macro converter? These increase the focal length of a lens so bringing things closer. But the minimum focusing distance remains the same so you can get large magnifications.

Extension tubes move the lens elements away from the film plane, which is what you do when you focus a lens closer, but more so. So again you get very close up pictures.

There are some good books on photographic optics if you want to pursue the theory, otherwise, give it a whirl and see for yourself what the various effects are!

NiMH batteries are fine for the *istDS - Sue and I use 2300 mAh and have had very good battery life and no problems. So 2500's should be even, albeit marginally, better.

The key to NiMH batteries is to charge them fully, use them fully before recharging, and also to bear in mind that they will not be at peak performance until they have received a few charges.

Hope that helps!

I think we've now come full circle (of confusion?) and it seems we pretty much agreed in the first place! Point 2 above of matt's was what I have been saying - in all practical terms, smaller formats will give you more DOF, very small fomats will give you masses of it!

I hope anyone who has followed all this has found some increase in understanding

Thanks, Matt, that is true.

I'm a great believer in actually shooting pictures to get personal experience of these things, and as in this example if you use a 50mm Macro to shoot a picture, and then a 100mm Macro to do the same picture (you will be further away) then both should have the same DOF. However, the perspective will be entirely different, which is the important effect.

If, on the other hand, you take a 28mm shot and a 100mm shot and then enlarge the centre of the 28mm to give the same picture, then the wide angle shot enlarged will have increased DOF. The perspective will also stay the same because our position has not moved.

Anyone who wants to try doing these and similar tests can prove it for themselves, which is much better than reading it in a book!

Well "Circles of Confusion" seemed to go down very well, nobody got confused, and it was kept to a straightforward practical level.

Then the questions started.....and we survived that as well!

Actually, I love all this lens stuff, but it is all inter-related and it can get very complex and completely out of hand.

And just as we were doing so well, someone said "What does boke mean?" and it all started off again. Fantastic!

This is why it's a minefield.

The final print size is indeed a different degree of magnification from the original. In addition, depending on the focal length, the distance you view the print is also a factor, although this relates more to perspective.

The circle of confusion will be a different value for different formats, and thus the resolution needed will vary to compensate for this. Small formats will need very high resolutions compared to larger ones to make similar print sizes. Again, we can compare say a 10"x8" negative which requires a fraction of the resolution of a 35mm one to make the same size print. At a given aperture, your 10"x8" negative will not have the depth of field of the 35mm one. Even a Rolleiflex 6x6cm negative has demonstably less DOF than 35mm.

The difference is that in a practical sense things are true that become less true as we dissect them.

Whilst we're at it, I might as well throw in that on smaller formats the depth of focus is more critical than on larger ones. I'll let someone else explain the difference between depth of field and depth of focus, something that lots of well known writers have got confused for many years....

Ironically, my club talk tonight I have titled "Circles of Confusion" as it's all about lenses, but strictly from a practical point of view.

I'll let you know how I do, and who ends up the most confused! Isn't this fun?