Close Examination of Fuji X-Series Lag Time

Started Nov 25, 2014 | User reviews thread
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Easycass
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Close Examination of Fuji X-Series Lag Time
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Introduction

The results below show the lag experienced when using certain Fuji X-Mount lenses with both the X-E1 and X-T1. This lag is defined in this case as the time from pressing the shutter-release button to the capture of the image in MANUAL FOCUS. This is not testing the AF system, as AF is not involved at all.

These tests are to investigate why it appeared that while in manual focus mode, at some apertures, for some lenses, and after certain focus operations, there was an apparent variable lag in capturing images.

The results of these tests can hopefully be used by Fuji to investigate if there is some issue that can be overcome in the future by either design or software performance enhancements.

The results of these tests, plus the observations and conclusions follow below.

Test Procedure

  1. X-T1 is set-up in front of a video monitor with test lens connected, in manual focus mode.
  2. The X-T1 is set for internal timer mode, set to fire every 6 seconds for 25 shots. In the case where the X-E1 was tested, shots are initiated via a remote release every few seconds instead of an internal time.
  3. Camera was set to automatic ISO, auto shutter speed, and manual aperture. Small jpegs were selected as output.
  4. An image preview is set to show for 0.5 seconds after the shot is captured.
  5. A running stop-watch timer is run on the video monitor, showing at least minutes, seconds, and down to 1000th of a second.
  6. A video camera is set-up behind the X-T1 test camera and the whole test videoed start to finish.
  7. When the 25-shot sequence is initiated, each time a single shot is initiated, the rear-panel live-view freezes momentarily, and once the camera fires, the resulting shot is shown. Using the video footage after the complete test sequence is completed, the difference between the timer on the frozen view and the timer on the post capture image is the time used to indicate lag for each shot.
  8. During the test, every five frames, a change is made, as follows: -

1) Frame 01 - Start with wide open aperture, with last turn of the lens barrel anti-clockwise.

2) Frame 06 - Set stopped down aperture (likely F11, F16 or F22, depending on lens)

3) Frame 11 - Adjust lens slightly clockwise

4) Frame 16 - Adjust lens slightly anti-clockwise

5) Frame 21 - Adjust lens slightly clockwise

Results - Lag time in ms (milliseconds)

X-E1 X-T1 X-T1 X-T1 X-T1

56   35  56   60  18-55 mm

F11  F16 F16 F16 F22

Lag  Lag Lag  Lag Lag    Frame/Comment

101 099 100 067 056    01 Wide Open - Focus ACW

100 068 100 101 100    02

136 101 102 100 066    03

101 099 102 101 100    04

100 099 102 069 100    05

468 199 235 233 200    06 Stopped Down

500 198 202 201 168   07

534 199 202 233 202   08

468 199 202 201 200   09

500 199 201 201 200   10

233 266 468 335 201   11 Focus CW

267 334 201 335 200   12

267 300 434 334 200   13

300 265 435 367 198   14

332 266 464 333 202   15

500 235 231 199 200   16 Focus ACW

466 200 233 235 200   17

500 164 168 199 201   18

467 199 235 201 201   19

534 199 201 199 201   20

265 266 432 332 200   21 Focus CW

333 233 466 334 200   22

299 301 435 335 201   23

299 267 433 333 200   24

300 266 400 334 200   25

Statistics

Avg Avg  Avg Avg Avg

108 093 101 088 084 - Wide Open

290 276 417 337 200 - Stopped-Down - After Focus CW

494 199 211 210 197 - Stopped-Down - After Focus ACW

Observations

In performing the tests, the following points were noted: -

  1. The X-E1 and X-T1 show slightly different performance characteristics.
  2. All lenses showed an increased lag between shooting at a wide-open aperture versus a stopped-down aperture.
  3. Some lenses showed a greater lag than normal when a manual or AF-button activation slightly moved the focus of a lens.
  4. In general, all lenses were able to maintain a lag time of around 100ms. This lag increased to approximately 200 to 250ms when lenses were used with a stopped-down aperture. A move of the focus of the lens in caused an increase in lag in some cases to more than 500ms.
  5. You can see that for the X-E1, the tests for the 56mm showed an increased lag to about 400-500ms when the lens was slightly rotated in a anti-clockwise direction, where as with the same lens for the X-T1, the lag increased to when the lens was rotated clockwise. When the lens was rotated in the opposite direction, the lag on both cameras would drop back to the normal stopped-down lag of around 200-250ms.
  6. It can be seen that on the lag induced by focus change could cause an increase based on the direction the focus was moved, but this in itself was not entirely predictable, with a difference in the effect based on lens, aperture, focus distance and camera.
  7. On the X-E1, using the 56mm lens, it was difficult to find a pattern when adjusting focus at F16. At F11 however, it followed a similar pattern as the X-T1 at F16. In fact, both cameras have somewhat varying reactions to this focus adjustment depending on the actual aperture chosen, with F8 lag showing the least reaction to any focus adjustment, but F2.8-F5 and F11-F16, most lenses exhibited some change in lag due to focus change.
  8. Occasionally, the pattern of turning either clockwise or anti-clockwise to cause an increase or decrease in lag, was not predictable, and seemed itself to be influenced by the actual absolute focus distance that the changes were made. It was difficult in the short tests made to fully ascertain how to predict the exact pattern of lag-changes according to focus adjustment.
  9. When a lens has been had its focus adjusted, at a stopped down aperture, when the shutter-release button is half pressed, as the aperture blades are moved to the stopped-down position, the characteristics of the audible sound sourced from within the lens changes. This is best described as follows: 1) when the lag is within the 200ms range (normal), the sound is a definitive short 'click' at shutter-half press, and a longer click-motor sound when the shutter is unpressed. 2) When the lag is within the 300-500ms range (longer lag than normal), the sound sequence is reversed, with a longer click-motor sound at shutter-half press, and a definitive short 'click' sound when the shutter is unpressed.
  10. While the camera was set to automatic ISO, auto shutter speed, and manual aperture, many different settings were tried at various times prior to testing, and there were no discernible differences to the test results given changes to ISO mode, display on/off, histogram/NR/lens-modulation on/off etc. It is believed from this pre-testing of setting changes that the underlying issue being tested here is not associated with such digital setting refinements of the camera.
  11. Note that during the test, a clockwise-turn of the focus ring means to change focus to a point further away in front of the camera. In the X-T1 settings menu, the Focus Ring setting is set to 'clockwise'. When doing the test, a turn of the focus ring was about 60 degrees of rotation, enough to move the focus motors/elements in the lens in the appropriate direction, but not enough to take the video monitor stopwatch out of focus (the large DOF of the stopped-down tests helped in this regard).
  12. It is agreed that the method of testing the timing is rather crude, and unlikely to yield accurate absolute timing values, but since the method of timing is the same for all lens tests here, this allows some confidence in using the relative times between the various settings to be compared.
  13. While these tests were performed using one owner's equipment, it has been tested on a second X-T1, 56mm and 35mm lenses, yielding the same result. Therefore, while not conclusive, it can at least be established that the equipment set used in these tests is likely to be similar in performance to other sets out there.
  14. These tests were done with the latest firmware available at the time of writing: 25 Nov 2014.

Lens Summary Results

  • The 18-55mm and 18mm (not shown in tests) lenses exhibited almost zero change in lag to the focus adjustments performed, at any aperture. This makes these two lenses the best performing in terms of predictable lag. They both showed a stable lag of around 100ms when wide open, and 200ms when stopped down to any aperture. These are the best performing lenses of the set tested.
  • The 35mm lens exhibited some change in lag to the focus adjustments performed, at most apertures. The lag was 100ms wide open, about 200ms when stopped down, and about 300ms when influenced by a focus adjustment.
  • The 56mm lens exhibited a lot of change in lag to the focus adjustments performed, at most apertures. The lag was 100ms wide open, about 200ms when stopped down, and about 400 to 500ms when influenced by a focus adjustment. This is the worst performing lens.
  • The 60mm lens exhibited moderate change in lag to the focus adjustments performed, at most apertures. The lag was 100ms wide open, about 200ms when stopped down, and about 330ms when influenced by a focus adjustment.

Videos

All tests can be viewed on YouTube here: -

X-E1 56mm https://www.youtube.com/watch?v=fLf1rc8DjNk

X-T1 18-55mm https://www.youtube.com/watch?v=xHk0F-IlHRc

X-T1 35mm https://www.youtube.com/watch?v=CFb3CdVZKHA

X-T1 56mm https://www.youtube.com/watch?v=BC6yl7YA5jw

X-T1 60mm https://www.youtube.com/watch?v=4dErrEVMzS8

Conclusions

From these tests, one can conclude that the lag time, between firing the shutter and capturing the image, is variable according to what camera and lens is being used, the aperture selected, the focal length of the lens, the focus distance and any adjustments in focus.

Whilst under test conditions it is possible to somewhat predict might happen at a given aperture, with a given lens, at a certain focal length and focus distance, the huge number of variations and combinations of these parameters made it impossible to come up with a general rule to allow one to predict the lag under normal shooting conditions.

It is unclear what is happening to cause this extra delay after a focus adjustment, but the audible noise that can be heard from the lenses give some clue that there is some extra mechanical activity taking place before exposure at the time the lag is greatest.

Whether or not this lag variation can be resolved for the affected lenses, in this case the 35mm, 56mm and 60mm, through a firmware update is not clear. The internal design may actually make it necessary to have such variable delays. However, it seems possible that there may in fact be some way to improve the performance, eliminating the extra delay, by not reacting to the focus adjustments, since these adjustments do not seem necessary in the 18mm and 18-55mm lenses.

This whole issue may become mute if the next firmware available in December 2014 addresses the issue.

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