I've uploaded five jpgs to my gallery for comments on my focusing performance at 300mm. I bought the D7100 18th May and thought right! from now on any focus issues are down to me! They are shots of Bob Atkins resolution chart taken using 70-300mm f4.5/5.6. Labelled Af Trials 1 to 5, they should be in order of best to worst focusing technique.
1. Manual focus, LiveView at max, Tripod, VR OFF 2. AF focus, Fine=tune ON at -8, Tripod,VR OFF 3. AF focus Fine-tune off, Tripod, VR OFF 4. Hand-held VR ON 5. Hand-held, VR OFF
Question. Is res of 6.3 best that can be achieved from 70-300 f4.5/f5.6? Question. What res should I expect if I upgraded to say a 70-200mm f2.8? Question. How to improve my technique in shot 4
#2. "RE: D7100 Focus issues" In response to Reply # 0
Brian, I think you miss understand how that chart is to be used, and your set up makes any results somewhat unreliable to me.
According to Bob Atkins, you're suppose to at a minimum use 5 charts printed at 4x6 inch and place them on a larger chart of 15x22 inch (one in center and one in each conner) and fill the frame with the larger chart. Your also supposed to make sure the chart is as parallel to the sensor as possible.
Given that your chart seems to be at an angle, the lighting seems somewhat variable with the white-balance all over the place, the illumination minimal if not insufficient with a slight under exposure makes any results unreliable and suspect (contrast and relative tonality has an impact on perceived sharpness).
When testing and attempting to fine-tuning AF, you need to be meticulous in your setup.
#3. "RE: D7100 Focus issues" In response to Reply # 0
St Petersburg, RU
It would appear that the different AF and MF settings are not limiting as much as the lens is wide open at 300mm. There is little difference between hand holding with and without VR at 1/320 second shutter speed. Did you try shorter focal lengths? Did you try stopping down to a better aperture for IQ, like f/8? The tests were hampered a bit by under exposure. LiveView is the mode that would tell you what the lens is capable of and since that was not that much better than tuned or not, hand held or not, the lens is not delivering what it is capable of. Try stopping down to the sweet spot on that lens of f/8 and compare LV tripod to the f/5.6 that you used for these.
The 70-200 is very good but the comparison, where the 70-300 is better also, needs to be a 200mm.
With PD AF being so close to LV, you can be assured that the AF module is adjusted well. Stan St Petersburg Russia
#4. "RE: D7100 Focus issues" In response to Reply # 3
Thanks for the replies. Yes Pete, I obviously fired off without even a basic understanding of what I was after, as, having now read Bob Atkins’ blog, apart from other mistakes, I was using a resolution chart to check focus issues!
I’m not really interested in the arcane technology of lens optics, but rather was trying to use some of the easy tests to improve the final focus/resolution of my photos.
Fine-tuning raised its head after noticing that my Tamron macro lens pictures seemed the sharpest, then I found that the fine tune adjustment for that lens was zero, but the other lenses needed a tune.
Stan I think has pointed out the right road for me, which is to investigate finding the best combinations of aperture and focal length for each lens and end use. That’s if I am understanding this time!
Out of interest, why did white balance change so much when light levels seemed constant between shots? Is Auto WB that jumpy?
#5. "RE: D7100 Focus issues" In response to Reply # 4
>Thanks for the replies. >Yes Pete, I obviously fired off without even a basic >understanding of what I was after, as, having now read Bob >Atkins’ blog, apart from other mistakes, I was using a >resolution chart to check focus issues! >
Well it's ok to use a resolution chart for focus testing, as long as its parallel to the sensor and well lit.
>Stan I think has pointed out the right road for me, which is >to investigate finding the best combinations of aperture and >focal length for each lens and end use. That’s if I am >understanding this time! >
Personally I find the 70-300 VR an excellent performer on a DX body. I find no appreciable advantage in stopping it down from wide open especially in the center.
>Out of interest, why did white balance change so much when >light levels seemed constant between shots? Is Auto WB that >jumpy? >
Without knowing more specifics its hard to say. AWB is designed to operate between 3500 and 8000K. If the light source is outside that range than your WB will be off.
What light sources were you using. It appears you were indoors near a window so tungsten lighting and sky light could be mixed making WB difficult. Not to mention deep shade sky light (9000 to 10000K) and tungsten (2300 to 3000K) are both out of the range of AWB.