Widening my approach

[DonSchap]

Like I said ... it is the real punch for having the TAMRON ... clearly, it's not perfect, but it is darn good!

There also might have been a little bit of back-focusing involved, because I was really close to its M.F.D. ... which can trip a lens up. The camera may "approve" a shot, even though the focus is a little off. The PRIME is good down to 8-inches, where the 17-50 is around 18-inches. I will conduct other analysis, as time permits ... but the thrust of this was that the PRIME is really good ... and obviously, would be a clear asset on the α900.

[Rooz]

don under the conditions you tested almost any lens is gonna perform well. you could test out the kit lens, stop it down, add light and you have case for just sticking with the kit lens. if you;re buying a 20/1.8 lens to use in a light tent for product photography then you've wasted your money. where the sigma will shine is in low light. it will have better sharpness, better contrast, better AF and better colour than the tammie...by some distance.

[DonSchap]

Well, I am pressed for set-up time. I'll have more next week. This weekend is shot, already ... and it is not even Friday ... well, at least not HERE!

f/2.8 is not all that closed down ... and I was not shooting the examples for noise determination, just a comparative focus test. Adequate lighting ... just makes it easier to see.

Yes ... bigger tests lie in the future and it should be kind of fun to see "how low can you go."

Thanks for the chime in ... we'll get there.

[DonSchap]

Okay ... I finally got the TAMRON SP AF 14mm f/2.8 Aspherical (IF) Rectilinear lens. This one really pulls it wide on the A900 ( oh yeah, I still am missing the FF body ... hmmm, have to work on that. ) So my wide lenses are filled in ... with seriously wide aperture.



I am not a big proponent of "second-hand" glass, and got this one off ebay ... but, this was purchased by the 'source' at a "close-out" sale and it is effectively "brand new" in the box w/ receipt. Yeah! Six-year warranty, starting now!

I want to thank 'jimr-pdx' for the inspiration to seek out and obtain this lens.

A couple examples ... soon.

[dr4gon]

Wow, that would be ridiculous on an A900!

[dr4gon]

Don't like to bump old threads, but I found myself trying to understand full frames better today and they really are just a larger frame. APS-C sensors are literally crops of the full frame, the bokeh is the same (the DOF is also the same). As Don pointed out however, the FOV (field of view) is different, much larger and wider. See here

http://www.have-camera-will-travel.c..._sensor_-.html

[DonSchap]

There is nothing wrong with resurrecting old threads. In fact, that's how the research is done and newbies get a chance to review important aspects of the craft. Not everyone had a SONY A100 three years ago. A lot of what is relevant can be pulled right back into the forefront for all of the members.

I had a member recently write me an IM and reference a posting of mine from 12/2007. It concerned lens repair, but is still just as pertinent NOW as it was then. So, relax about opening the door to the past. It is from there we often decide our future.

[Rooz]

APS-C sensors are literally crops of the full frame.

what did you think it was ?
the bokeh and dof are not quite the same either.

[dr4gon]

what did you think it was ?
the bokeh and dof are not quite the same either.

Wait, what? I thought the DOF and Bokeh were pretty similar. Are they not supposed to be the same ? You would know now owning a D700.

[Rooz]

nope, not the same. if i take a photo with my 50mm lens at 1.4 its not the same bokeh or dof as if i took it with the d300. there are small differences in things like smoother colour transition, light to shadow transitions etc. small yes, but having shot the d300 i know when something looks a tad different. sometimes for the good, sometimes for the worse.

while in essense what you said is correct, its not quite as simple as saying that aps-c is simply a smaller image circle. for example, the pixel photosites are completely different sizes on aps-c you are squeezing 12mp's into a smaller area. on FX you are squeezing the same amount of MP's onto a larger surface area. so it would make sense that there are small variations in the way these photosites respond to light etc.