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 on: July 04, 2016, 02:23:00 PM 
Started by klindup - Last post by Bob Atkins
Batteries life depends on both the battery design and how it's used. For a typical Li-ion cell life is maximized if it's not fully discharged and not overcharged (or even charged to 100% capacity). I don't know if this applies to the Cannon batteries and charger but I assume the charger cuts off early enough to prevent any premature aging of the battery. I'd also guess that the camera shuts down before the battery is truly fully discharged to avoid shortening the life.

Typical numbers for a Li-ion cell might be 1000-1500 cycles of 95% to 50% charge/discharde before capacity drops to about 75% of the original capacity.

My experience is that at the true "end of life", the battery simply won't hold a charge or will refuse to charge. As long as the battery seems to take and hold a charge, I just keep using it (and carry a spare of course!).

 on: July 03, 2016, 11:30:39 PM 
Started by klindup - Last post by klindup
Thanks Bob
I will continue to use the battery and carry a spare with me.

 on: July 03, 2016, 12:16:55 PM 
Started by klindup - Last post by Bob Atkins
The only risk I can think of is that you might run out of battery power sooner then you would expect. As they age batteries will take less charge so their capacity diminishes. However I don't think there is any danger of damaging the camera. Battery voltage doesn't increase and older batteries don't explode.

Canon are probably very conservative in their estimation of "end of useful battery life", just like they are very conservative when they tell you a cartridge has run out of ink!

 on: June 27, 2016, 01:06:00 PM 
Started by klindup - Last post by klindup
When I check the status of the battery recharge performance in my 60D I see one red cell illuminated which suggests that the battery has reached the end of its life.  But the battery seems to charge ok and hold charge.  Can anyone tell me if I am taking a risk in continuing to use it?
Ken Lindup

 on: May 17, 2016, 09:10:48 AM 
Started by Fotobuff - Last post by Fotobuff
Thanks for the advice. Now I have to figure out how to make the best compromise between different requirements.

 on: May 15, 2016, 11:28:09 AM 
Started by Fotobuff - Last post by Bob Atkins
I looked at quite a few small tripods last year and my pick of the bunch was the Slik Sprint 150 ( It offered the best "bang for the buck" in terms of stability, flexibility, size, weight and cost.

With any small tripod you are going to have to come to some compromise between weight, height and stability. If you don't extend the legs, stability of any tripod will increase, so you have to also balance shooting height against stability.

There are literally dozens (if not humdreds) of choices, but you have to first figure out how much you are willing to spend, how much weight you are willing to carry, how high it has to extend and what kind of load it has to handle in order to narrow down the selection. The  Slik Sprint 150 was my pick for an inexpensive tripod weighing under 2.5 lbs, extending to >60", capable of supporting a DSLR with a small/medium lens and it costings under $60.

 on: May 14, 2016, 09:06:38 AM 
Started by Fotobuff - Last post by Fotobuff
I am looking for a light travel tripod which should also be stable enough to support a dslr camera and lens without any shake. Can someone recommend a few models with varying material of construction, price and weight.

A light tripod which should also be stable at the same time seems to be a contradiction in terms. How is this achieved ?

Please also mention the minimum and maximum height as also the folded length.

Thanks for your help ! Smiley

 on: May 05, 2016, 04:47:16 PM 
Started by klindup - Last post by Frank Kolwicz
It seems to me that most people think about mirror lenses when they either are looking for a small, light, cheap alternative to expensive, heavy, long focal length camera lenses or are looking for extreme magnification, 1200mm plus. I’m not sure what use they have in mind for the images, as the out-of-focus highlights (the bright doughnuts) are generally considered rather ugly, a kind of ultimate anti-bokeh, that makes the images mostly unsuitable for exhibition or publication. (This is my opinion, after all, not the 11th commandment.)

Once you take into consideration that mirror lenses are manual focus, you find that your choice of comparable photographic refractors with the same limitation and at about the same price extends your choice to many old and therefore cheap models from several manufacturers. The reasons then for going with a mirror lens become much smaller – essentially light weight and compact size. The fixed and relatively small aperture is another hindrance that can be avoided with a photographic lens.

There are so many choices for proper photographic lenses in the under-600mm range that would be equal or superior in use to a mirror lens, that I can only imagine one use for a mirror lens: for extreme back-packing or trekking to record observations of a scientific or personal nature where image background and out of focus quality is of no concern.

As to long focal length uses, the description of the cost of and difficulties handling the big mirror lenses previously described should be enough to put off any consideration of them as replacements for camera lenses of about 1200 mm or more. Beyond 1200mm there are also difficulties getting sharp images due to camera movement and atmospheric aberrations under all but ideal conditions. The highlight doughnuts everywhere in the image (since almost all of the image will be out of focus) is a killer – I know, I’ve been using a Canon 600 with 2x converter with a 7dii for birds (effective focal length 1920mm) and atmospheric aberration at distances where the long focal length was needed has wasted all images on some days and most images, most days. Only when the atmosphere was extraordinarily calm could I get reliably sharp images at that focal length. The longer the focal length, the worse the problem! And, don’t forget, no image stabilization, either.

All in all, there are good reasons why mirror lenses are of little interest for terrestrial photography.

 on: March 30, 2016, 04:49:11 PM 
Started by klindup - Last post by Bob Atkins
Mirror lenses can be pretty good - as well as small, light and inexpensive. They can also be not so good.

See my review of the Pro-optic 500/6.3 lens

It's cheap ($160 when tested) and nominally reasonably fast ("f6.3"), but unfortunately it's not all that sharp and the T-stop is closer top f10 than f6.3.

The Tamron 500/8 (discontinued) is much better, plus it's actually smaller and around the same price (if you can find a used one). If you must have a long lens and can live with the limitations of a mirror lens (fixed, slow, aperture plus manual focus and "do-nut" out of focus highlights), it's not a bad choice.

 on: March 29, 2016, 09:20:31 PM 
Started by klindup - Last post by klindup
I take your point about telescopes being so heavy and bulky and that lenses designed to be used on cameras are the best option.  I also have a Televue NP 101 bought for observing but which makes a great 540mm f5.4 lens if the walk from the car is but a few yards.  The weight of the telescope and the Gibralter mount needs two trips to set up and a third to fetch the camera.  However if I can find a suitable site the images I get of birds are great and worth the effort.  But not the first choice when looking for a 500mm lens.

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