stngoldberg
Well-known member
Would someone please define what the centerfold effect is on a medium format back like a Hasselblad HD60
Thank you,
Stanley
Thank you,
Stanley
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centerfold effect
- Thread starter stngoldberg
- Start date
I have a vague understanding what it is, but it would be nice if someone can contribute with an exact technical description too. Here's the vague version:
CCDs have amplification electronics off chip, and to speed up readout there's more than one channel. If those channels are not exactly calibrated you get a distinct difference in levels between the channels, so you get a centerfold. Even on a well-calibrated back you can see the effect by shooting a plain sky (or an LCC card) an increasing contrast to maximum.
When looking at the actual CCD chip you may see lines on it from that it has been exposed more than once during manufacturing (due to the large area). As far as I know those have nothing to do with the centerfold effect though, and are not visible in the image. Another common misunderstanding due to those lines is that the chip would be stitched together from several smaller chips, but it's not, it's just exposed by the ic stepper more than once.
CCDs have amplification electronics off chip, and to speed up readout there's more than one channel. If those channels are not exactly calibrated you get a distinct difference in levels between the channels, so you get a centerfold. Even on a well-calibrated back you can see the effect by shooting a plain sky (or an LCC card) an increasing contrast to maximum.
When looking at the actual CCD chip you may see lines on it from that it has been exposed more than once during manufacturing (due to the large area). As far as I know those have nothing to do with the centerfold effect though, and are not visible in the image. Another common misunderstanding due to those lines is that the chip would be stitched together from several smaller chips, but it's not, it's just exposed by the ic stepper more than once.
stngoldberg
Well-known member
Thank you Torger.
I am considering moving up to an H5D. My passion at this moment is using a technical camera; the H5D back has several important advantages over my H4D when mounted on my Arca R3MDI.
1. H5D back contains a clip on battery that frees me from carrying around my Imagebank and time necessary to connect and disconnect it.
2. H5D has a single dedicated zoom button (to 100%) plus the ability to scroll at 100% using the wheels on the body while showing the focus point on the back.
3. The back on the H5D is somewhat brighter.
I would entertain moving from my H4D50 to an H5D60, but I am concerned about the centerfold effect Woody Campbell reported when he owned an H4D50.
If anyone could shed any light on this query, I would be most appreciative
Stanley
I am considering moving up to an H5D. My passion at this moment is using a technical camera; the H5D back has several important advantages over my H4D when mounted on my Arca R3MDI.
1. H5D back contains a clip on battery that frees me from carrying around my Imagebank and time necessary to connect and disconnect it.
2. H5D has a single dedicated zoom button (to 100%) plus the ability to scroll at 100% using the wheels on the body while showing the focus point on the back.
3. The back on the H5D is somewhat brighter.
I would entertain moving from my H4D50 to an H5D60, but I am concerned about the centerfold effect Woody Campbell reported when he owned an H4D50.
If anyone could shed any light on this query, I would be most appreciative
Stanley
Stanley:
You may find this thread informative:
http://www.getdpi.com/forum/medium-...826-digital-sensor-centerfold-correction.html
Tom
You may find this thread informative:
http://www.getdpi.com/forum/medium-...826-digital-sensor-centerfold-correction.html
Tom
stngoldberg
Well-known member
Yes, I read that thread and I think the post by Pemiham is probably an excellent example of the centerfold effect
Thank you Tom!
Stanley
Thank you Tom!
Stanley