Diptera.info :: Identification queries :: Diptera (adults)
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 Meigenia sp. (Tachinidae)
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| Rui Andrade |
Posted on 10-03-2008 19:43
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 Member Location: Portugal Posts: 3122 Joined: 19.06.07 |
Sorry for the bad photo . Is it possible to tell the species?location: Barcelos, Portugal date: 08/03/2008 
Edited by Rui Andrade on 27-03-2008 01:57 |
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| Stephane Lebrun |
Posted on 10-03-2008 23:21
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 Member Location: Le Havre, France Posts: 8248 Joined: 03.03.07 |
Meigenia ?
Stephane. |
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| Rui Andrade |
Posted on 11-03-2008 23:38
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Member Location: Portugal Posts: 3122 Joined: 19.06.07 |
Thank you for your suggestion Stephane |
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| Zeegers |
Posted on 12-03-2008 21:51
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Member Location: Soest, NL Posts: 18787 Joined: 21.07.04 |
This is hardly a suggestion, seems 100 % correct. Theo |
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| Rui Andrade |
Posted on 12-03-2008 22:27
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Member Location: Portugal Posts: 3122 Joined: 19.06.07 |
Thank you Theo, for confirming the excellent "sugestion" of Stephane |
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| Tony T |
Posted on 12-03-2008 23:04
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 Member Location: New Brunswick, Canada Posts: 662 Joined: 08.02.07 |
Rui Andrade wrote: Sorry for the bad photo Not that bad a photo. The image is sharp and full of detail, but dark. Can readily be brightened in something like Photoshop. What happens is that cameras try to make every image having a brightness of a neutral grey; usually an 18% reflectance. Thus when you have a lot of white in an image, the camera typically underexposes to make the white more like a grey. If you have a dark fly on a white background the fly will be very underexposed - as in your image. If you have a dark fly on a dark background the camera will overexpose both the background and the fly to get everything grey with everything overexposed. The solution: If lots of white in a subject adjust the EV (exposure value) on your camera to +1 or even +2. If lots of blacks on your image, and you want to keep the blacks as black, then adjust the EV to -1. If lots of green in your image leave the EV at 0; plants give an 18% reflectance. |
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| Rui Andrade |
Posted on 12-03-2008 23:59
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Member Location: Portugal Posts: 3122 Joined: 19.06.07 |
Thanks a lot Tony, I really am needing those tips I'll try to do what you explained me, and I'm anxious to give it a shot. |
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| Zeegers |
Posted on 13-03-2008 18:52
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Member Location: Soest, NL Posts: 18787 Joined: 21.07.04 |
First class tip by Tony Theo |
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| Susan R Walter |
Posted on 14-03-2008 14:56
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 Member Location: Touraine du Sud, central France Posts: 1802 Joined: 14.01.06 |
In the studio/lab, it is better to set the white balance, which also adjusts for colour cast. In the field you usually don't have the opportunity/time to do this. To be honest, I usually fix this sort of thing from a field shot in Photoshop - but that's probably because I am a lazy point and shooter and Tony is a zillion times better photographer than me.
Susan |
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| jorgemotalmeida |
Posted on 14-03-2008 15:26
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 Member Location: Viseu - PORTUGAL Posts: 9295 Joined: 05.06.06 |
yeah, Tony is right. I use those tips all the time. And a good diffuser is important so the light can spread much better and don't concentrate just in one part of the object. |
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| Tony T |
Posted on 14-03-2008 15:38
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Member Location: New Brunswick, Canada Posts: 662 Joined: 08.02.07 |
Susan R Walter wrote: In the studio/lab, it is better to set the white balance, which also adjusts for colour cast. In the field you usually don't have the opportunity/time to do this. White Balance and Expoposure Values are not the same. In this image WB looks OK; the blacks on the 1st abdominal seg. and the 1st femur are pure (i.e., equal values of R, B, G) - no colour cast. The wall is a tad too green but this is probably correct as it will reflect some green from nearby foliage. Usually just leaving the WB at A works well for outdoor shots. This photo is underexposed (to us) but perfectly exposed from the camera's point of view (actually for the person who programmed it at manufacture). The camera should have a button "+/-"; pressing this button and turning a control wheel either clockwise or anticlockwise will change the EV values in 1/3 or 1/2 values. Plus values make the image brighter, minus values make it darker. This is what needs to be adjusted in the field (or in the studio). |
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