In fact, a stable subject should help the AF system track more reliably.
I didn't say it wasn't effective because it is. Your link reads that the lens uses a microcomputer that performs all kinds of instructions. It has to take longer, albeit mini seconds longer, then not using it. Here is a quote from your link describing a small function of what it does:
This instruction is transmitted to the stabilizer lens group that moves at a speed and direction to counteract the camera movement. This complete sequence is repeated continuously so that there is an instant reaction to any change in the amount or direction of the camera shake.
Remember we are all used to using Canon EF IS lens but they are much more effective then this IS/VC lens admittedly by several testers. Perhaps with the lens being less effective in image stabilization and the fact that is a slower lens that take longer to obtain focus at the long end, it might be more effective with faster shutter and VC off. Just a theory as to why some can't obtain AF at all.
Are these uncropped original frames? If not, can you post the uncropped originals for comparison? Is it possible for you to open the RAW files using DPP, zoom in to 100% and with active focus point shown and post a screen capture (see example below)? Thanks!
Thanks for taking the time to do that. One of the reasons you might not be getting the results you want is that it appears the bird is too far away. From these 100% crop-level screen caps, it appears that the bird is only occupying about 10% of the total frame. Tough task for AF, and not a lot of pixels to resolve details. There could be other factors such as atmospheric distortion, as well.
Thanks for taking the time to do that. One of the reasons you might not be getting the results you want is that it appears the bird is too far away. From these 100% crop-level screen caps, it appears that the bird is only occupying about 10% of the total frame. Tough task for AF, and not a lot of pixels to resolve details. There could be other factors such as atmospheric distortion, as well.
Not ideal situation & still early day as I said.
These were only a few shots that were kind of in focus.
My analysis was based on other 200+ shots that I shot that day. Focus Point hitting right on the head but bird is out of focus - no motion blur... just plain out of focus. I will give another try may be on a sunny day & I am very hopeful that this lens will deliver.
sfink161 wrote:
Doesn't the camera have to incorporate with the lens and use the processor to do so? The processor has more processes to perform with VC (IS) on. I've actually seen speed test in the past on this and yes it definitely takes longer with it on. It's no different then the processor on your computer or phone. The processes, the longer it takes to complete it's task.
No, IS does not slow down AF:
Chuck Westfall says the AF potentially works faster and more accurately with IS on.
"You would be better off with the IS version for skiing photos, for a reason that might not be obvious at first glance. Although chances are good that you'll be using a shutter speed so fast that the IS system has no effect, use of IS will present a steadier image to the camera's AF detection system. Thus, if you're using predictive focus, the IS system may provide better data for the AF system to base its calculations on. However, if you're just zone focusing manually and waiting for the subject to pass through the area you've preselected, then you might as well shut off the IS function and save some battery power."
Question number eight here: digitaljournalist.org/issue1002/tech-tips.html
Again, IS on does not slow down AF, indeed it might be beneficial to AF performance even when shooting at shutter speeds that don't necessitate it. If you don't agree go tell Chuck ...Show more →
OK, I'll take Chuck's (and your word) word for it. It's just hard to imagine where the computer world has come to from my old mainframe COBOL programming days where you could set the speed of processing single programs by the sundial rather then the microprocessors of today where you better not blink or you miss something. You had to be efficient to gain every minute of speed when writing code.
sfink161 wrote:
OK, I'll take Chuck's (and your word) word for it. It's just hard to imagine where the computer world has come to from my old mainframe COBOL programming days where you could set the speed of processing single programs by the sundial rather then the microprocessors of today where you better not blink or you miss something. You had to be efficient to gain every minute of speed when writing code.
For the Canon in-the-lens IS, the camera just signals the lens to do it's IS thing, starting when you half press the shutter button (or press the rear button, if set to up to focus). The sensing and processing for IS all takes place in the lens. Notice the write up on the Canon site.
sfink161 wrote:
OK, I'll take Chuck's (and your word) word for it. It's just hard to imagine where the computer world has come to from my old mainframe COBOL programming days where you could set the speed of processing single programs by the sundial rather then the microprocessors of today where you better not blink or you miss something. You had to be efficient to gain every minute of speed when writing code.
Sharpness advantage clearly goes to the Canon but at 10x the cost(whatever it cost I'm not sure) and extra weight I'm not putting up that kind of money. I can't justify it.
sfink161 wrote:
Sharpness advantage clearly goes to the Canon but at 10x the cost(whatever it cost I'm not sure) and extra weight I'm not putting up that kind of money. I can't justify it.
Not only that, but we're comparing a ZOOM lens vs. a PRIME lens with a TC. That's a bit of an unfair competition right there.
I think the Tamron does remarkably well in this comparison.
I spent some time again today with Canon 7D & the New Tami.
Was a cloudy day with patches of light. Fortunate to get these flying birds around
Canon 7D, 600mm. ISO 640, 1/1600. F6.3, +1 EV, Center Point with assist points, Conti Shot, AI Servo, ~75% of original image American Black Duck by Photosequence, on Flickr
cameron12x wrote:
Not only that, but we're comparing a ZOOM lens vs. a PRIME lens with a TC. That's a bit of an unfair competition right there.
I think the Tamron does remarkably well in this comparison.
I don't think it is unfair to compare a prime with TC to a zoom. Actually, modern zooms lose little to nothing compared to primes in the same class even without TC.
The problem with the comparison above is that the images are not identically focused. You can see it in the wires in the lower left part, where you can see through. The wires behind are more in focus in the Tamron image, so the main subject is probably slightly out of focus.
While it is a reporting TC, it obviously does not report its presence to the Tamron, or the EXIF would show 840mm and would not show the f-stop at f6.3.
