V/F delay - why has nobody questioned this?

Started Jul 7, 2012 | Discussions thread
Aku Ankka
Aku Ankka Contributing Member • Posts: 591
Re: Answers and a measurement (for a cell phone)

Michael J Davis wrote:

Aku Ankka wrote:

Michael J Davis wrote:

This depends on one's tool. I have no idea on how much lag differen m4/3 cameras offer, but my current tool has undetectable amount of lag. Your post made me test it against some animations as I'd never noticed any lag, and when used against high frame rate animations, reality and the image on the EVF were registered by my brain to move simultaneously. When using low frame rate animation (like 15 fps), the animation as seen by the eye directly was occasionally one frame ahead. So in reality the reality as seen directly by the eye and the reality seen indirectry, though the EVF present no lag on my camera.

That's interesting. 15fps represents 67ms per frame. I don't know what the refresh rate (i.e. the time it takes to 'paint' the frame is) but I'm surprised at the 'normal' refresh rate being as low as that. If you try to take a photo of, say, a golfer striking a ball while looking through your vf, you'll miss the point of impact by a long way!

You misunderstood a bit - being occasionally one frame behind does not mean that the lag would be 67ms. Most of the time both views on the animation were simultaneus, but as the 15fps and the frame rate of the camera are not in sync, occasionally there can be one frame hickups. A higher framerate animation was different. The real lag is likely to be in the ballpark of what the screen refreshrate itself is.

I just retested the viewfinder with the 60fps animation and there was no lag visible of anykind, not even a frame's worth. What was funny though is how my brains did a few time think there is a frame of lag, but that was for the live view, not the EVF view Our brains are entertaining

We are told that Live view cameras are getting closer & closer to DSLRs in performance, but ISTM that the live view delay is still a limiting factor compared with the speed of light through the optical system.

For my camera (a competiting system)


Not relevant.

such limitation does not exist. Instead the conventional SLRs have the extra issue of slow moving mirror and only the most expensive professional high speed shooters come close to the speed of my camera when it comes to reaction time. I am sure the m4/3-cameras are also superior in reaction time to most SLRs due to the lacking slowness of the mirror.

Some of the pro DSLRs achieve 15fps in continuous mode - that doesn't sound that slow. (granted entry level cams are somewhat slower.)

There are no SLRs which allows for 15fps with the mirror moving . Nikon D4 offer 11fps. The new Canon should offer 12fps. It is very difficult and expensive to move the mirror at those (or higher) speeds.

While there can be slight lag, it may appear to be longer than it actually is due to the relatively low frame rate of the animation.

No, it doesn't work like that. It's the change that shows, where there's a difference between what the two eyes see: the eye can 'know' there's a difference down to around 1/50th sec (20ms).

You missed my point - if the animation doesn not have a high enough refresh rate and is not synchronized with the cameras VF frame rate, the lag is not constant and may give the impression on it being larger than it actually is.

I do agree that we can see small differences, however the 20ms is already not only difficult for the brain (not the eye) to notice without concentrating on it, but also so little that is is almost irrelevant for the VF purpouses (every mirror on DSLR is significantly slower).

Now Dpreview (and as far as I'm aware other review sites) have never attempted to measure this delay (I recall some early commentary suggesting that it could be as high as 300msm but cannot find this now.)

300ms would be so apparent that people would be returning their cameras as faulty items. I just checked out my dirt cheap phone's camera and it has lag of about 15-30 ms.

You must have a very good dirt cheap phone. Mine is well into the 200ms lag. (see below)

A chinese Huawei smartphone - the camera is lousy though. I should have mentioned that the lag depends heavily on the amount of available light - in low light the framerate slows down, thus the lag increases as well.

2. How come that reviewers are so keen to record continuous shooting speeds to the nearest ms, but ignored this major handicap in the compact camera challenge to DSLRs?

Because it is not a handicap, or at least is should not be. If a crappy cell phone has almost non-existing lag - less lag than what the movement of a mirror in DSLR is, it would be very surprising if m4/3-cameras had more.

I'm amazed at your phone! A simple lag test is to hold your hand with fingers spread in front of the camera and wave it up and down at a frequency of about 2-3 per sec.

This is not a great test as you need to have enough light - in low light the viewfinder may appear laggier depending on the implementation. The cell phone of mine gets worse, while the camera remains solid (though becomes noisy when light is low, if very low, noisy and laggy).

I went to http://boallen.com/fps-compare.html and with one eye looked at the animations of known frame rates, and the other looked at them through the viewfinder. The same with the camera and it's view. (One may want to remember that one's computer display's frame rate has slight influence as well.)

One problem with today's EVFs is that only a very small part of the sensor surface is used to record the image (often even less than what is used for movie recording). This means that when the light levels are not high, either the EVF will become noisy, or it becomes sluggish, or both.

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