Shutter Speed for the D750

[BackdoorArts]

I'm having a brain fart. :concern:

Do I remember reading you auto-tuned your lenses while they were wide open near the long end? I wrote a post about that after reading an Amazon review where the guy said to auto-tune that way. Logically it makes sense. Yet I thought @BackdoorHippie said it didn't work well that way (or so I *think* that's what he said).

So the question is: what settings did you use while auto-tuning your 70-300mm lens?

Not sure what you mean by "auto-tune" - perhaps the focus tuning calibration adjustment? On zoom lenses I ascribe to the prevailing wisdom that, all things being equal, you calibrate to the long end of the zoom, wide open. Sometimes, however, all things are not equal and AF adjustment can swing wildly at extremes. For example, on something like a 70-300mm you could be somewhere like -3 to -7 from 70mm to 250mm, and then all of a sudden at +4 at 300mm. That's where you need to make a decision based purely on usage. This level of deviation isn't typical, but a deviation at the extreme isn't unusual, so knowing how your lens acts can help you make your decision. In a case like this, I'd set the calibration for the bulk of the lens sweep (probably around -3 or -4) and know that when I'm at 300mm I want to close down the aperture and boost my DoF.

 

[hark]

Not sure what you mean by "auto-tune" - perhaps the focus tuning calibration adjustment? On zoom lenses I ascribe to the prevailing wisdom that, all things being equal, you calibrate to the long end of the zoom, wide open. Sometimes, however, all things are not equal and AF adjustment can swing wildly at extremes. For example, on something like a 70-300mm you could be somewhere like -3 to -7 from 70mm to 250mm, and then all of a sudden at +4 at 300mm. That's where you need to make a decision based purely on usage. This level of deviation isn't typical, but a deviation at the extreme isn't unusual, so knowing how your lens acts can help you make your decision. In a case like this, I'd set the calibration for the bulk of the lens sweep (probably around -3 or -4) and know that when I'm at 300mm I want to close down the aperture and boost my DoF.

Thanks for the explanation, Jake. And yes, I meant focus tuning. Not sure why I wrote auto tune.

And for Don, my 70-300mm is noticeably softer when zoomed out to 300mm. I try to keep it at 280mm or less.

 

[voxmagna]

I found something similar happening last week when I shot flower petals with the 85mm lens. Everything confirmed the focus point live and in post, but the image was soft to me. I'm wondering if the AF although appearing to confirm locked, isn't on the focus point when you have flat areas without detail? That zoo animal with fur will be hard to AF and at (say) 30 feet and you only have just over six inches DOF. I'm going to start using manual focus a little more - what you see should be what you get. I've already put a DOF calculator on my phone which has taught me a lot. My big gripe is the D750 does not show the focus distance until you extract it from the EXIF in post.

 

[voxmagna]

I found this thread link which might help others:

D750 soft or out of focus: Nikon FX SLR (DF, D1-D5, D600-D800) Talk Forum: Digital Photography Review

In addition and to help with camera shake issues, I've discovered features in the Auto ISO settings. I'm not an enthusiast of Auto ISO but you can control how much the camera could use. The D750 has this feature when AUTO ISO is set of only allowing 1/focal length minimum shutter speeds when you work in Aperture and Shutter priority modes.

You will need to remember you set the options if you want to use a tripod and longer shutter times. I thought about this and if you are in low light hand held, there is no choice but to use a wider aperture and change the ISO or under expose. You can see ISO in the viewfinder and if it is too high for your chosen aperture (noise), you get a tripod or add light. I found this feature really useful for my zoom lens. If you use VR zoom lenses a lot you can change the 1/focal length default to reduce the minimum shutter threshold and take advantage of image stabilization. When you choose Full Manual setting, there is no automatic shutter speed limit restriction and it is easy to forget with a zoom lens that YOU have to apply the shutter speed > 1/focal length rule.

Setting AUTO ISO 'on', limiting its range and using the minimum shutter speed feature should help reduce camera shake leaving you with exposure, focus and DOF to get right. If you are a 'shaker' you can set the minimum shutter threshold higher.

 

[kurt78]

When using tripod, there is still the movement of the subject. The necesary shutter speed depends on a lot of other factors like mooving subject angular speed, pixel density in sensor.
https://photographylife.com/what-is-reciprocal-rule-in-photography

After a little math I discovered for example:
Athlete running 20 km/h from side to side at 5m distance without panning using a 50mm lens (or 35 on DX).
If I use a D40 (3000 pixels in a 24mm sensor) the blur I get shooting a 1/1000 is about 5 pixels.
If I shoot the same with a D7100 (6000 pixels in a 24mm sensor) I get double of pixels blurred.
D800 is even whorse, with 11 pixels. That's because of how many pixels are in one cm.
D750 is (6000 pixels in a 36mm sensor) with a 50mm is the same as de D7100 with a 35mm.
So, I would need to use speeds of 1/8000 to really freeze that athlete or pan the camera following the movement.
(I haven't cheked the numbers, it's just a physics point of view)