[Lowell Goudge]

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wouldn't the pentax DA* 50-135 fetch more in resale? Adorama lists one for $799 brand new.

There are two groups of DSLR users ,those who take advantage of the crop factor and downsize their lenses for smaller asp-c sensor equivelents, and those who like to Take advantage of the crop factor for more reach. In fact as mike noted many use the 70-200 with a TC

resale value is not, for me a critria when I get a lensin 30 years of photography, the only thing I sold was my darkroom

[Pentaxor]

I think the release of the new Sigma 70-200 would affect the market value or resale value of the first Sigma 70-200. from the looks of it, the new Sigma has a different optical material and design that might display a much better result than the first 3 generation of the 70-200. if the new 70-200 costs at around 800-$1000, then the new Sigma would be more of a better investment. an additional $150-$400 is worth it, IMO.

[Mike.P®]

I think the release of the new Sigma 70-200 would affect the market value or resale value of the first Sigma 70-200. from the looks of it, the new Sigma has a different optical material and design that might display a much better result than the first 3 generation of the 70-200. if the new 70-200 costs at around 800-$1000, then the new Sigma would be more of a better investment. an additional $150-$400 is worth it, IMO.

In the UK the new 70-200mm f2.8 will retail is the equivilent of $1800. I know we pay quite a bit more here for our electrical/photographic gear but I'm pretty sure it will be more than you think in the USA. To be honest I can't see it affecting the MKI .. the lens has already done its price dropping and the reason it held it's price is because its so good in comparison to the newer versions.

As far as I am concerned the new Sigma lenses are purely for the Canon/Nikon crowd, hence built in OS which we already have. I had the pleasure of using the new Bigma OS for a few days on a 7D last week and if I'm honest the camera was very very good but the lens itself is no better than my Pentax mount Bigma .. it was just easier to handhold on the Canon.

[Pentaxor]

In the UK the new 70-200mm f2.8 will retail is the equivilent of $1800. I know we pay quite a bit more here for our electrical/photographic gear but I'm pretty sure it will be more than you think in the USA. To be honest I can't see it affecting the MKI .. the lens has already done its price dropping and the reason it held it's price is because its so good in comparison to the newer versions.

As far as I am concerned the new Sigma lenses are purely for the Canon/Nikon crowd, hence built in OS which we already have. I had the pleasure of using the new Bigma OS for a few days on a 7D last week and if I'm honest the camera was very very good but the lens itself is no better than my Pentax mount Bigma .. it was just easier to handhold on the Canon.

Mike, as you said, the new Bigma OS is no different from the Pentax version. the only difference between the 2 as you stated is the OS for the Canon/Nikon users. but as Samsung announced, aside from the OS feature, the other 3 new lenses (including the 70-200) have a different optical design and added FLD elements and additional SLD elements which the Bigma doesn't have. if a bit more optimistic that they might be cheaper because Samsung might have found a cheaper material with excellent optical quality to use or they purposely made an aggressive move to make them cheap inorder to create and attain influence in the lens market. earn by the volume as the chinese say it. I do admit that the premium you pay in the U.K. is double as compared to North America. and I do feel bad for you guys. I also never really have the thought of even buying laptops there which are just outrageously expensive.

anyway, I'm just wondering as to why Sigma didn't include some FLD elements on the Sigma 85/1.4.

[Mike.P®]

anyway, I'm just wondering as to why Sigma didn't include some FLD elements on the Sigma 85/1.4.

From what I can see on other forums (multi brand) if the price is right they could make it out of jam jars and it will sell by the bucket load.

[rustynail925]

Just some questions regarding a 2x TC
i heard that when you use a 2x TC on the f2.8 it will become f5.6
is this right? coz i was able to use a 2x TC and manage to shoot f2.8

[Mike.P®]

Just some questions regarding a 2x TC
i heard that when you use a 2x TC on the f2.8 it will become f5.6
is this right? coz i was able to use a 2x TC and manage to shoot f2.8

Pentax cameras do not recognise teleconverters (apart from their own 1.7x) so will report the aperture as if it were not there. This also means the SR will not be working at it's best.

[Lowell Goudge]

Just some questions regarding a 2x TC
i heard that when you use a 2x TC on the f2.8 it will become f5.6
is this right? coz i was able to use a 2x TC and manage to shoot f2.8

Pentax cameras do not recognise teleconverters (apart from their own 1.7x) so will report the aperture as if it were not there. This also means the SR will not be working at it's best.

the issue is not pentax but sigma, (and also some other TC Makers)

the sigma TCs feed the electrical data straight through to the camera, unmodified.

As a result the aperture and focal length are the lens without TC, this has 2 issues,

first of all, the camera needs to know the aperture for correct metering. This is specifically true of the K10D and K20D where the focusing screen is very irregular in performance as a function of aperture, and these are corrected by the camera body and software. By feedig through the lens data, the camera thinks it has an F2.8 lens as opposed to an F5.6 lens and the exposure is not correct. It requires about a 1.5 stop correction as the lens plus TC combo will tend to over expose.

second, the focal length is reported again right from the lens, which causes the shake reduction, and also program lines to be set for the lens not considering TC. SHake reduction performance is therefore not optimal, and the lens will in hyper program mode pick the wrong shutter speed, usually too slow, because it is not using the correct focal length.

[rustynail925]

ic. so you mean the aperture will be a5.6 but appears as 2.8 ?

[Egg Salad]

Yes, effective aperture is two stops (exposure values) slower with a 2X TC. In this case you would have a f/5.6 lens but an unchanged display on the camera. However, due to open aperture metering exposure should still be correct (split prism screens aside). Don't know if they are other drawbacks aside from wrong exif data.

[Lowell Goudge]

Yes, effective aperture is two stops (exposure values) slower with a 2X TC. In this case you would have a f/5.6 lens but an unchanged display on the camera. However, due to open aperture metering exposure should still be correct (split prism screens aside).

Unfortunately this may not be true and is a real problem expecially on K10D and K20D

the stock focusing screen, with manual lenses has a metering problem that is programmed out with A lenses.

BUT since the teleconverter reports the wrong effective aperture, there is a metering error introduced.

see the chart below for metering with manual lenses.



If you consider a lens at F2.8 on the K10D for example, but it is really at F5.6 there is a huge error in the way the camera meters. each 45 greyscale is one stop, and with almost a 100 change in greyscale for F2.8 to F6.6 on th e*istD there is a 2 stop difference. the lens will over expose with a TC unless you put in exposure compensation

[Arpe]

first of all, the camera needs to know the aperture for correct metering. This is specifically true of the K10D and K20D where the focusing screen is very irregular in performance as a function of aperture, and these are corrected by the camera body and software. By feedig through the lens data, the camera thinks it has an F2.8 lens as opposed to an F5.6 lens and the exposure is not correct. It requires about a 1.5 stop correction as the lens plus TC combo will tend to over expose.

I've never "corrected" my exposure when using TCs using my istDs, K20D, and K-7. All my thousands of TC pics come out fine. The camera can see how much light is coming through and meters for it.

Surely if the camera thought it was 2.8, but with the TC it was 5.6 (so less light), the pics would be underexposed, not over? My belief is that the camera meters the light it sees, it doesn't matter what f stop the camera thinks it's using.

[Nerdold Nerdith]

Pentax Sigma 70-200 mm f2.8 APO EX (excellent) - eBay (item 250609644124 end time Apr-11-10 12:55:47 PDT)

[rustynail925]

I just got the sigma 70-200 and the TC. Can i use the Sigma 2x TC on any pentax K mount lenses?

[Mike.P®]

Can i use the Sigma 2x TC on any pentax K mount lenses?

No, only if they have a deep recess where the rear element is as the Sigma has a protruding front element.