Tamron 90mm F2.8 DI flash performance

[grado]

Hi,

I have a little problem with the Tamron 90mm f2.8 macro DI and D70. When using flash on distances more than 2 meters, the pics turn out overexposed. I have to add negative exposure compensation or put to manual mode to overcome that problem. Macro distances and short distances with flash is ok. Does anyone encounter that problem too? Thanks!

[ortega]

all pictures? of any lighting situation?

Flash used?

can post sample pix?

[grado]

Originally Posted by ortega all pictures? of any lighting situation? Flash used? can post sample pix?

All pictures are affected(over exposed) regardless of colour of subject when more than 2 meters away with flash. Without flash, exposure is accurate enough.

Here are some quick test shots in the room with room fluorescent light and some ambient window light. I stood around 50cm, 1 meter and slightly more than 2 meters respectively. The pics are compressed with Irfanview but you can see the exposure error quite clearly... Shot with in built flash on the D200, but with SB800, would be the same results too. The D70 i tested also gave similar results.







Forgot to add all shot at maximum aperture, F2.8 that is...

[zac08]

I'm guessing that the close up pictures aren't over-exposed due to the fact that the metering is correct to show up the colours correctly when the subject fills up the whole image. But when you stand further off, there is a large patch of white or blank area which may fool the metering system that you chose. (here I'm guessing that you are using Matrix system)

just my 2 cts of guesswork,

[grado]

Yes I was using Matrix system. But since now I have more "white" space when I stand further at 2 meters, won't that fool the camera into underexposure, rather than overexposure for this case?

[zac08]

I'm not exactly very sure here... But I did find that the flash seems to over-expose when I choose a larger aperture when doing macro shoots.

Was trying out some product shooting last night in my light tent and I found that my cam overexposes when it's f4 or larger.. in the end, I stuck to f11 for better results (D200 + 60mm micro and 2 x SB-600)

[grado]

I see... Thanks for your reply. Was wondering if anybody has a D70/D200 and tamron 90mm F2.8 DI and can do a similar test to see if they get the same result as me?

[ortega]

what was the meter reading at the point of exposure?

if the meter was already correctly exposed, then the flash output would have cause the over exposure.

try it again with the meter set to under expose
does the T90 have a chip to communicate the distance to the camera+flash?

[grado]

The ambient light was underexposed at the setting that were taken at F2.8 and 1/30 seconds. So i guess its the flash metering mistake?

[tanhb]

I agreed with ortega, it might be the flash that cause it.

Set your flash mode to TTL instead of TTL-Balance, on the camera, set flash compensation to negative. Start with -1.7 or -2 ev. Try out, see any improvement.

[gooseberry]

Think it's because for the third picture, even though the ambient light is underexposed for your settings (ISO 160, 1/30sec, f/3), even with flash at minimum power, it will cause some parts of the image to overexpose (the white t-shirt). For these situations, you will need close down your aperture/reduce your ISO/increase your shutter speed.

[gooseberry]

Originally Posted by ortega does the T90 have a chip to communicate the distance to the camera+flash?

Yep, the T90 has a distance chip.

[gooseberry]

Originally Posted by tanhb I agreed with ortega, it might be the flash that cause it. Set your flash mode to TTL instead of TTL-Balance, on the camera, set flash compensation to negative. Start with -1.7 or -2 ev. Try out, see any improvement.

Yes, it could also be due to the TTL-BL. Try using standard TTL instead, if you are using the internal flash, you can only get standard TTL in spot metering mode, if you're using the SB-800, just press the mode button until you see TTL and not TTL-BL.

[grado]

Originally Posted by gooseberry Think it's because for the third picture, even though the ambient light is underexposed for your settings (ISO 160, 1/30sec, f/3), even with flash at minimum power, it will cause some parts of the image to overexpose (the white t-shirt). For these situations, you will need close down your aperture/reduce your ISO/increase your shutter speed.

Its not just the white T shirt that is over exposed, its generally the whole image. Its definitely not minimum power as with the same aperture setting, the close distance of 50cm and 1 meter did not overexpose.

[grado]

Originally Posted by gooseberry Yes, it could also be due to the TTL-BL. Try using standard TTL instead, if you are using the internal flash, you can only get standard TTL in spot metering mode, if you're using the SB-800, just press the mode button until you see TTL and not TTL-BL.

Hey, I got the break through! I tried in spot metering mode, and in standard i-TTL, the flash exposure are accurate again! Thanks guys! I learnt something new today! Dunno why in Matrix BL-TTL mode, this lens dun function well at a distance...

[lsisaxon]

Originally Posted by grado I see... Thanks for your reply. Was wondering if anybody has a D70/D200 and tamron 90mm F2.8 DI and can do a similar test to see if they get the same result as me?

There are 2 conditions for this to happen.

1) If the SB-800 is early 2005, underexposure will occur for distances less than 1m, even with Nikon lenses (tested on D70s, D200 and D2X). The problem does not exist for newer (2006) SB-800 with Nikon lenses. Only workaround to this problem is to use Auto mode (not even TTL) with the older flash. I'm not sure if a firmware upgrade is available for the flash from NSC.

2) If a 3rd party lens is used. This is more erratic. Tested on D70 and D70s, SB-800 does not work very well. Exposure may sometimes be over and sometimes under. The problem is worse with SB-600.

[ortega]

Originally Posted by lsisaxon There are 2 conditions for this to happen. 1) If the SB-800 is early 2005, underexposure will occur for distances less than 1m, even with Nikon lenses (tested on D70s, D200 and D2X). The problem does not exist for newer (2006) SB-800 with Nikon lenses. Only workaround to this problem is to use Auto mode (not even TTL) with the older flash. I'm not sure if a firmware upgrade is available for the flash from NSC. 2) If a 3rd party lens is used. This is more erratic. Tested on D70 and D70s, SB-800 does not work very well. Exposure may sometimes be over and sometimes under. The problem is worse with SB-600.

that looks like a manufacturing fault
if the flash does not work as it should then
it would be wise to bring it back to NSC and have it fixed

[grado]

My SB 800 works ok with other lens, except for the Tamron 90mm F2.8 DI in TTL-BL mode at distances more than 2 meters... In normal i-TTL mode it seems accurate enough.

[_espn_]

The other time furball/acidbyte used the 90mm on their D70/D2H with flash work ok leh.

[unseen]

You wanna check something?
The aperture blades on your tamron 90mm may be stuck, may not close down to the aperture you set.