Processing times

[Rich K]

following the star trails thread I've been snapping away at night
and noticed that there is a large amount of time taken up with the camera (D7000)
busy before the next shot can be taken.

At the weekend upon the advice of what I see as a reputable dealer,
I bought a Sandisk Extreme Pro 95MB/s SD card to replace my Sandisk ultra 15MB/s

this afternoon I thought I would check the speed difference

30 sec exposure

Extreme pro took 32 seconds before able to take the next pic (£40.00)
Ultra took 32 seconds before able to take the next pic (£11.00)

whats going on here?
do I have settings wrong
did I get poor advice
card to fast for the camera

is this the standard performance?

I dont understand ...... can anyone explain?........(in simple terms)

cheers

[mrmr96]

Digital noise reduction on long shutters will take the same amount of time as the exposure. It can be turned off. (PS - it's nothing to do with the speed of the memory card.)

[Simpo Two]

Yep - RTM.

[Rich K]

Thanks guys,hope this educates others as well as me.

What are the benefits of faster cards?

might sound like a stupid question but I really dont know

R

[LongQ]

Rich K said:

Thanks guys,hope this educates others as well as me.

What are the benefits of faster cards?

might sound like a stupid question but I really dont know

R

Writing large files.

Writing lots of large files at a high frame rate and being ready to take the next shot.

Video - maybe - depending on the output write speed of the video camera.

High read speed for downloading everything when you have a card full - providing you are are reading it with something that can use the available speed and into something that can write quickly enough ....




Point 2 is particularly noteworthy for sports, some wildlife, reportage and, perhaps, fashion shoots.

The last point may be of significance for all.

[Rich K]

mrmr96 said:

It can be turned off.

with Long exp. NR turned off it took less than a second.

All I need now are some clear skies ans some stars

It'll be interesting to see if the lack of NR makes a big difference to the pics

[Rich K]

LongQ said:

Writing lots of large files at a high frame rate and being ready to take the next shot.

I see ...... just shot a salvo of 6fps (max resolution and JPEG finest quality)

Extreme pro slowed after 42 shot

with the ultra slowing after just 20

I'm learning all the time ......Ta

[mrmr96]

Good cameras will have a memory buffer, which will allow several shots taken close together. The buffer fills as shots are taken, it's emptied as the shots are written to the card. If the memory card can write less data per sec than you're generating per sec on average then the buffer will eventually be full and you'll have to wait. A faster card allows the buffer to drain faster than you're taking shots (unless you're really going fast on the shutter!!) so you never get a delay as the buffer is never filled.

[LongQ]

Rich K said:

LongQ said:

Writing lots of large files at a high frame rate and being ready to take the next shot.

I see ...... just shot a salvo of 6fps (max resolution and JPEG finest quality)

Extreme pro slowed after 42 shot

with the ultra slowing after just 20

I'm learning all the time ......Ta

Shoot RAW or RAW+JPG and the performance becomes more significant although wider factors, as mrmr2 has described, come into greater play.

Of course for shooting long exposure at night the difference may be minimal. Your shot to shot downtime would not normally be affected much by card write speeds these days uness the camera is very short on buffer capacity or some new camera feature (inbuilt HDR perhaps - something along those lines) uses it all. Even then the write time of the resulting file may not be very different in real terms.

That said if using something that produced a very large file - medium format for example or maybe even a D800 - the write times of a very much slower older card could be rather evident. (Assuming the limit is not in the camera body itself - also an area of recent data transfer speed developments.)