[hcc]

In a previous thread (https://www.pentaxforums.com/forums/172-pentax-k-3/261483-uhs-memory-card-burst-rate.html), I reported some very preliminary tests on the burst speed of the Pentax K-3 in High continuous shooting mode. I obtained then results comparable to the review results of imaging-resource.com, but below the results obtained by Adam in the in-depth review and definitely below the review results of dpreview.com. In the discussion, Adam suggested that there might something to do with AF mode, while member wtlwdwgn mentioned something about half pressing AF.

So I went back to some basic tests that I will list below.

In summary: using a MF lens, I achieved performances of 8.2 fps (H) and 4.6 fps (M) in line with Adam's review results.

A important point hinted by member wtlwdwgn: you need to keep pressing (relatively hard) the AF button for the full duration of the burst. As soon as you release the pressure on the AF button, I found that the burst rate dropped.

I hope to continue further tests. I use Hi continuous shooting all the time and I believe that the shooting mode is great, quiet and perfect for any action shooting. Anyone with his/her own data on the burst speed is welcome to add these to the thread below to assist other users.

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My limited data - Bursts of less than 7 s - MF lens - JPEG files L (* and **)
Hi - Tests with VL58mm MF
8-9 fps with JPEG file L* & Sandisk ExtremePro 95 Mb/s 8Gb (Average: 8.2 fps)
Med- tests with VL58mm MF
4-5 fps with JPEG file L* & Sandisk ExtremePro 95 Mb/s 8Gb (average: 4.6 fps)

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Last edited by hcc; 05-13-2014 at 05:41 PM.

[Adam]

One other thing to note is that your subject may also affect the write speed, since the resulting JPEG files are smaller for more uniform scenes This would introduce a bit of variability when comparing multiple independent tests.

[lister6520]

What shutter speed are you using? Unless you are using fast shutter speeds the frame rate will necessarily be lower. I have consistently got between 8.5 and 8.7 at 1/500s.

The battery type and charge can also cause a significant reduction. I don't know the extent of the effect except for a perceived significant reduction when using a third party LiIon battery. I was using a new genuine Pentax battery for the test. NiMH batteries in the grip would probably also be slower than the LiIon battery, due to the higher internal resistance but I am unable to test that as I don't have a battery grip.

I used audio recordings to measure the rate.

[hcc]

What shutter speed are you using? Unless you are using fast shutter speeds the frame rate will necessarily be lower. I have consistently got between 8.5 and 8.7 at 1/500s.
The battery type and charge can also cause a significant reduction.

I used 1/80 s shutter speed and a fully-charged battery (no grip). I did further test and I got 8.3 fps on average +/-0.1 fps so far

I intend to do more tests and I will share these when I have more conclusive data.

[OregonJim]

It seems to me that these are all reasonable frame rates. The limiting factor (not counting shutter speed) is pure mechanics and could easily vary slightly between cameras. Spring tension, amount of lubrication, motor torque, mirror weight - all these things will vary slightly and are designed with manufacturing tolerances in mind. Heck, even altitude, temperature, and barometric pressure can cause differences!

Is there a real world application where a fraction of an fps discrepancy makes a difference?

[RonHendriks1966]

Variation in these numbers are normal I think. Most tests are done with 1/250th or faster shuttertime for optimal performance.