Will this lense fit

firemedic0135 · Jan 16, 2007

I have an old minolta QTsi with the original lense and a 75-300 lense both af and am wondering if they will fit the new sony alpha a100.
I am going to buy a new dslr but cant decide on the rebel xti or the sony alpha. the alpha definantly feels good in my large hands and the rebel feels like a toy but there are absolutly houndreds of options with the rebel that are not available for the alpha.Thanks in advance for any help.

Don Simon · Jan 16, 2007

The QTsi was part of Minolta's 35mm autofocus system, Maxxum aka Dynax aka Alpha. If the lens works on that it will also work on the Sony Alpha.

Now I'm curious, what are the hundreds of options that are not available for the Sony?

firemedic0135 · Jan 16, 2007

well just from my shopping around i have seen hundreds of lenses for the rebel and lots of info on them but none on the alpha.I do realize that the alpha is newer and the first from sony.I just have a bad habit of buying things that are somewhat less versitile than similar products and just trying to avoid that again.

Also should I spend the extra 150 bucks for the kit lens 18-70 I believe or stay with the body only and use my original 35-80 lens from the qtsi?

thanks and sorry if I seem a bit nieve,I am just getting started and there is alot of info to sort through.

Don Simon · Jan 16, 2007

I understand the problem. Now is a difficult time to be choosing an SLR system, with new stuff being released all the time, new features and specifications popping up everywhere, and a lot of money required for the initial investment.

Canon do have more lenses than Sony. But I believe Sony will still have more than enough to cover most needs. In fact they have lenses that Canon and others don't. No system can cover every conceivable need. Also bear in mind that as you said there is not a lot of info on them... that doesn't mean they don't exist. There are plenty of Sony-branded lenses available, plus of course all the autofocus Minolta or Konica-Minolta lenses will also work on the Alpha. That's before you start looking at the Sigma, Tamron and Tokina lenses that will also work. I don't think the Alpha would be less versatile from that point of view.

The Alpha may be the first released by Sony but it's based heavily on the technology and design of Konica-Minolta's previous digital SLRs (the 5D and 7D) and I believe when Sony took over Konica-Minolta's photo business they took on quite a lot of expertise from that company. Add in all the Konica-Minolta products (flashes and other accessories as well as the lenses) that have been rebranded Sony (and of course the original ones will still work on the Alpha), and you have quite a few options.

As for the lens, I would go for the kit lens. Because of the 1.5x "crop factor" of the Sony, your 35mm-80mm when used on that will be more like using a 50-120mm on your film camera. The 18-70mm lens on the Alpha will be roughly equivalent to 28-105mm on 35mm film, which is probably more useful if you do anything remotely wide-angle.

firemedic0135 · Jan 16, 2007

if you could explin the crop factor to me please as long as it doesnt require too much on your part.
Thanks

what whould the crop factor be for my 70-300mm?

Don Simon · Jan 16, 2007

This might explain it better, but I'll give it a go anyway.

"Crop factor" is basically just a way of comparing the field of view you get with a lens on a digital sensor smaller than 35x24mm, with the field of view of the same lens on a 35x24mm sensor or film area.

The sensor on an Alpha 100 is less that 35x24mm. It is 23.6x15.8mm. 35 divided by 23.6 is roughly 1.5. 24 divided by 15.8 is roughly 1.5. The field of view with a lens of a given focal length is therefore roughly 1.5x smaller than it would be if the same lens were used on a 35x24mm sensor or film area.

What this basically means for you is that if you were used to using a particular focal length on 35mm film you need to divide that focal length by 1.5 to find out what focal length you need to achieve the same effective field of view on the Alpha. For example if you were used to using a 50mm lens on 35mm film, you would now need something between 30mm-35mm to get the same field of view on the Sony Alpha. If you used a 105mm lens on 35mm film, now you need a 70mm lens.
This works the other way too of course, you can use it to find out the effective field of view of your current lenses when used on the Alpha. Just multiply by 1.5. Therefore your 70-300mm effectively compares to using a 105-450mm lens on your 35mm film camera.

This is not limited to the Sony Alpha. It's not a purely digital thing either, for example a 50mm lens on a medium format camera will give you a wider field of view than a 50mm used on a 35mm camera.

Sony's crop factor of 1.5x is shared by Nikon and Pentax DSLRs. Canon's lower to mid range models have a 1.6x crop factor, and their higher-end and professional models are 1.3x or 1x i.e. a full-frame 35-24mm sensor. The crop factor on Olympus dSLRs is nearer to 2x.