Guessing - as are we all.
Camera is a D700.
User had a bright fixed amplitude light source and wanted shallow DOF and good quality.
They chose ISO 200 for quality.
They chose f/4 for minimum DOF.
Given aperture and ISO, and light amplitude controlled, shutter speed was the remaining variable required to balance the exposure correctly.
DOF seems about right given aperture and range with that focal length.
DOF is already shallower than the eyelet front to back width and about lace width. They had up to f/2.8 available which would have made DOF less than lace width at the eyelet location (it's marginal now) which would have compromised apparent sharpness.
Here is an online Depth of Field Calculator
Use D300 for D700.
At what I estimate distance to subject to be (250mm or less) DOF is even less than we see here at those settings. This suggests it is a crop rather than a compressed full frame. (At 105 mm distance is 250mm or less and DOF is under 2mm!). Macro setting on lens may change effective focal length.
Somewhat related, maybe ... below here.
DOF
f = focal length
N = Aperture f number
c = circle of confusion
s = subject distance (assumed >> f)

from Wikipedia DOF
c ~= 0.025mm for FF 35mm.
c ~= 0.018mm typical crop APSC.
see Wikipedia COC
Some more DOF calculators ..... agh
Many provide hyperfocal distance as well.
Overkill department:
Hyperfocal Distance
Source: See at end.
Setting focus at the Hyperfocal Distance gives maximum depth of field
from H/2 to infinity.
H = (L x L) / (f x d)
Where: H = Hyperfocal Distance (in millimeters) L = lens focal
length (ie, 35mm, 105mm) f = lens aperture f-stop d = diameter of
circle of least confusion (in millimeters)
for 35mm format d = 0.03
for 6x6cm format d = 0.06
for 4x5in format d = 0.15
Near Focus Limit
NF = (H x D) / (H + (D - L))
Where: NF = Near Focus Limit (millimeters) H = Hyperfocal Distance
(in millimeters, from above equation.) D = lens focus distance (in
millimeters) L = lens focal length (ie, 35mm, 105mm)
Far Focus Limit
FF = (H x D) / (H - (D - L))
Where: FF = Far Focus Limit (millimeters) H = Hyperfocal Distance
(in millimeters, from above equation) D = lens focus distance (in
millimeters) L = lens focal length (ie, 35mm, 105mm)
Source: Material on hyperfocal distance which is absolutely identical to the above appears on dozens if not hundreds of websites and has been available over many years. A number of sites say the material is for private use only or copyright BUT do not indicates that in fact it is from another source and probably public domain for decades. The actual formulae ARE public domain. I certainly do not intend to attribute the material to any site which has copied it from elsewhere without saying so.