D90 Problem?

Allan FG

I was shooting a desert motorcycle race today and I'm noticing some of my shots have a very different exposure even though the EXIF reads the same for 2 images shot in the same second.

Both of these read as 1/200th F13 ISO 200, they are of the same rider and you can see that they were taken in the same second. The shot right after these two has good exposure. I haven't seen this behavior before and I would be interested if anyone else has seen this before.

angevin1

Considering the left side of the 2nd photo is lighter, it looks like a bit of Shutter lag.

ziggy53

As Tom noted I am a bit concerned about the "uneven" exposure. It does look like a shutter mechanism issue.

Rob_W

Did you have Vr turned on ?, if your shooting continuously with Vr
switched on it can cause weird effects with the shutter.

Allan FG

Rob_W wrote:

Did you have Vr turned on ?, if your shooting continuously with Vr
switched on it can cause weird effects with the shutter.

I did have VR turned on, I have never seen this behavior before and I have shot heavy with VR turned on before. I'm wondering if a good cleaning would help, couldn't hurt.

Allan FG

Well I think it has to do with shooting RAW, I filled one card with RAW images and then I switched to a smaller card so I also switched the camera to JPEG, I didn't see any of these type of images with the JPEG images. I think I was just overloading the camera.

Rob_W

What speed SD card did you have in ?.

Allan FG

Transcend 8 GB Class 6 SDHC Flash Memory Card TS8GSDHC6E

Rob_W

At 6mb/s transfer speed its probably your card slowing things up, shooting in
Raw your transfering a lot of data to the card and when shooting continuously
it has to transfer very quickly.

I use Scandisk Extreme III Cards, they have 30mb/s transfer speed which are
a lot quicker than the ones your using. They are a bit pricey but speed is
never cheap i'm afraid.

If it was the shutter sticking or needed cleaning i think it would show up a
lot worse than that, it does look more a processing problem...


.

Rob_W

I just noticed one of the reviews on the amazon site...

Bought to replace my broken class 6 card for my D90. There is a noticeable difference in speed especially when shooting burst. With class 6 I could fire off about 13-15 shots until the buffer ran out but with this one, I can keep shooting continuously. Great speed and with 8gb it has plenty of space for any situation.

Looks like thats your answer and on a D90 as well...

ziggy53

A memory card can impact on transfer speed and "occasionally" you will hear of the high frequency electronics of the camera internals affecting image quality via poorly shielded memory card, but that will be in the form of a repetitive "noise"; either banding or a noise that looks almost like sensor noise.

A card should have no impact on overall exposure, as I see in the second image. All modern cameras buffer the image internally before transferring the image to the memory card. The exposure is completely formed before the image is stored onto the card.

If the problem persists I suggest that camera repairs are likely needed.

Allan FG

Well I will do some testing and see what I can figure out. Thanks for all the replies.

Rob_W

Fair enough, i'll go along with that but why then does it only do it in raw?.
Once the exposure is completely formed its transfered to the card, the
only difference writing to the card is the size of the file and the maximum
transfer rate of the card.

It may well be a trait of a D90 when the buffer is full. It would be interesting
to put a fast card in and see if it still occured...