dorian wrote:
Why do a sharpness test at ISO 100/200 and 1/60 or 125 when most wildlife photography --- the target demographic for these lenses -- is usually done at higher ISOs and faster shutters? With shutters that slow, shake could be a consideration, even with electronic shutter Give me a sample representative of real world usage; otherwise it means little.
To test a lens its quite critical to use base ISO and give the lens its best shot. We are testing the lens after all, not the sensor.
1/60s is fine with a tripod, electronic shutter and wireless trigger. Then take 10-20 shots and pick the best one
dorian wrote:
Why do a sharpness test at ISO 100/200 and 1/60 or 125 when most wildlife photography --- the target demographic for these lenses -- is usually done at higher ISOs and faster shutters? With shutters that slow, shake could be a consideration, even with electronic shutter Give me a sample representative of real world usage; otherwise it means little.
Those are separate parameters. Many of us want to know about the IQ of the lens under static conditions, the best case. Ideally you do the lens tests indoors with solid support and flash or bright lights to eliminate any degradation from vibrations.
Then you can conduct a field test how the lens/camera IBID/tripod collar/mount/tripod works as a unit to conteract vibrations. The main issue outdoors is that the amplitude and vector of the vibrations (and image movement) are inconsistent due to wind or other factors. Handholding is even worse since all the muscles micro twitching, etc. in addition.
aCuria and EB-1 - What you say makes sense, thanks. But, if one has control of the lighting, why not set the test to allow for a faster shutter? That would make it 'more ideal' to me. Guess good enough is good enough. Anyway, we can leave it there. Cheers.
arbitrage wrote:
The 300GM only has 2 (as do the big boy 400/600).
I can tell you the 300GM can outfocus the 100-400/4.5 any day of the week and twice on Sunday.
I think the only reason they put 4 into the 100-400 is how heavy that creeping lens element is
I think that the reason for 4 motors in the zoom is that there are two groups that move by different amounts depending on both the focus distance and the focal length.
arbitrage wrote:
I thought reviews of the Viltrox 2x were similar to the Sony. But Abbott's results with the Viltrox 2x look terrible. I wonder if the Sony would be better??
The comparison between Viltrox and Sony TC I have seen showed rather significant differences. The Sony was noticeably sharper, but also had much more CA.
Jack Flesher wrote:
I am fine with that comment, noise increases with crop and the effective DoF changes with crop. But claiming that somehow makes the aperture vales equivalent is ludicrous. Aperture value is a constant in an exposure regardless of the focal length of the lens.
Equivalent aperture vales of a crop work the same as equivalent focal lengths and equivalent ISO values. They are not physical values. Instead they tell you what aperture, focal length and ISO you would have to use on a FF sensor to produce an equivalent image as the crop. An equivalent image is the same in terms of: angle of view, DOF, noise and diffraction. It is not the same in terms of: number of pixels involved and optical flaws.
Regarding the two lenses discussed here, when shot wide open both feature the same entrance pupil diameter. So when cropping a bird image from either to the same composition, both will produce equivalent images, whether shot with or without TCs.
billsnature wrote:
I already have the 600mm on pre-order, but I am still hoping to see a good test between the 400mm f4.5 and the 100-400 f4.5 obviously at 400mm and the 600mm f6.3 vs the 300mm GM with a Sony 2X TC.
Dustin Abbott's review of the 400mm provides a comparison to the 100-400mm at 400mm (14:20 into the video). The 400mm is just marginally sharper than the 100-400mm at the center and mid range. But the differences are small. He even concluded that the 100-400mm was ever so slightly sharper at the corners. While he did not comment on it, I see a little bit more contrast in the images from the 400mm vs 100-400mm.
