Foveon Funk

Next up is another problem I just noticed: SENSOR SPOTS :eek::eek::eek:


SDIM0023-small by areality4all, on Flickr

Notching the exp comp down by 2 stops in post makes the spot much more obvious:


SDIM0023 (-2 exp)-small by areality4all, on Flickr

Here's another photo in which that spot appears:


SDIM0031-small by areality4all, on Flickr

And again at -2 exp comp in post to make it more visible:


SDIM0031 (-2 exp)-small by areality4all, on Flickr

Okay, so now that we have established the existence of the spot, what is really interesting is to notice that the position of the spot has moved slightly in the two images.

(The lens is crystal clear, covered by a UV filter, also crystal clear).

When the DP2M first started shipping last year, there were some sporadic reports of sensor spots.

But why would the spot move, especially given its relatively large size?
 
i hadn't heard about the sensor spots. that's quite a problem on a camera without a removable lens.

fortunately, i haven't had issues with the red/green cast (haven't shot a lot outdoors with the dp2m yet), but i can definitely see it in the photos above. since i stink at post processing, i hope it's somehow avoidable.

i wonder if exposing to the right side of the histogram (before the highlights clip), and then pulling down the exposure in post as needed, would help avoid the color cast? i haven't read a lot on the issue, but i seem to remember that under or low exposure may exacerbate the issue.
 
dfatty said:
i wonder if exposing to the right side of the histogram (before the highlights clip), and then pulling down the exposure in post as needed, would help avoid the color cast? i haven't read a lot on the issue, but i seem to remember that under or low exposure may exacerbate the issue.
Click to expand...

Yes, it should. I've run into the green and magenta casts when I underexpose. However it appears NI is exposing properly and still having the issue.(?)
 
jsrockit said:
Yes, it should. I've run into the green and magenta casts when I underexpose. However it appears NI is exposing properly and still having the issue.(?)
Click to expand...

i don't have a calibrated monitor but it seems like there is room to go right without blowing the highlights on the first affected shot. for example, the affected shot looks more like the -2EC shot of the rooftop shot than it does the properly exposed rooftop shot. but that's all a guess without the file in front of me. and certainly no criticism is intended by this observation/guess, just trying to find a solution to the problem.
 
Overexposing. I'd read about that.

Interesting.

So let me share this with you all. The photo that I posted in the other thread titled "Alpenglow in the city" was actually overexposed by about 1.5 stops or more. When I took the photo I was actually pretty miffed about the overexposure, because I couldn't figure out why it was happening. Exp comp in fact had been dialed in at -0.3 on that shot. But it is true that in post processing, lowering exp comp by 2.0 stops, I came up with a really nice image.

Below is the SOOC jpeg, just so that you can how badly overexposed it was:


"Alpenglow" photo SOOC jpeg by areality4all, on Flickr

And of course here it is after conversion in SPP and some curves work in LR


Alpenglow in the city by areality4all, on Flickr

I still don't understand why the overexposure was happening. That was actually the first--and only--time I had tried using Landscape mode, so I was wondering if there weren't some connection there?

Interestingly, those overexposed shots were the best images from the day and the one that had no color cast problem. So that MIGHT be a fruitful avenue to pursue. However, it does present other problems (including speed problems while you're in the field trying to adjust everything, but heck, we all know this isn't a camera for Quickdraw McGraw).
 
noimmunity said:
What effect are you hoping for?
Click to expand...

It will correct the caste and some other minor adjustments.

But if you want something fancy, there is Perfectly Clear, the best auto correction software for still images.

But as always I don't understand why people shoot jpg, especially with Sigma cameras...
 
wow, that is quite a nice save on that photo, i wouldn't have thought you could get back so much detail.

i badly overexposed some photos on the dp2m when i accidentally had the camera on spot metering rather than evaluative metering. i had set it to spot metering because of heavy backlighting but then forgot to reset for later photos. i've accidentally left other cameras on spot but they never caused as much overexposure as the sigma did, so it seems like in some situations the sigma can really throw the exposure out of whack.

anyway, i suspect that your overexposure took you all the way to the right of the histogram without clipping the highlights. i say this because on the photos in which i metered wrong and overexposed, i had blown out the highlights so badly that there was no data to pull back. since you had no red/green casts, exposing to the right seems to have worked. :p
 
Exdsc said:
But as always I don't understand why people shoot jpg, especially with Sigma cameras...
Click to expand...

Rather than pondering your innate superiority, I suggest that you try instead to think for a moment. What would happen if I had tried to post the original X3F file here?

Do you know of a free file hosting site that would allow one to view and link to files in X3F format?

"Flickr officially supports JPEGs, non-animated GIFs, and PNGs. You can also upload TIFFs and some other file types, but they will automatically be converted to and stored in JPEG format." http://www.flickr.com/help/photos/
 
dfatty said:
wow, that is quite a nice save on that photo, i wouldn't have thought you could get back so much detail.

i badly overexposed some photos on the dp2m when i accidentally had the camera on spot metering rather than evaluative metering. i had set it to spot metering because of heavy backlighting but then forgot to reset for later photos. i've accidentally left other cameras on spot but they never caused as much overexposure as the sigma did, so it seems like in some situations the sigma can really throw the exposure out of whack.

anyway, i suspect that your overexposure took you all the way to the right of the histogram without clipping the highlights. i say this because on the photos in which i metered wrong and overexposed, i had blown out the highlights so badly that there was no data to pull back. since you had no red/green casts, exposing to the right seems to have worked. :p
Click to expand...

There is a very tiny loss of detail on one of the white buildings, but overall it worked really well.

It could be impossible though to verify something like that in the field, making bracketing almost obligatory. With file size already a concern (60mb for a high res X3F + jpg file), it's something I'd like to avoid.
 
noimmunity said:
It could be impossible though to verify something like that in the field, making bracketing almost obligatory. With file size already a concern (60mb for a high res X3F + jpg file), it's something I'd like to avoid.
Click to expand...

You're probably right about this, but at least it's still easier than having to bracket with film :eek:) I try to have the histogram on in liveview when I shoot, not that I always pay attention to it. But based on your experience I'm going to make a better effort to watch the histogram and expose to the right when shooting sky to avoid the red/green issue if possible. If it's a shot of something I really want I'll bracket, but I agree that bracketing every shot becoming tiresome and is a computer memory killer.
 
I recently setup my c1 for -2 0 + 2 plus multi frame to play w/ HDR.

But if u set your ev to +0.7 or + 1 and change the delta to +\- 1 instead it would give u a three shot sequence of -.3, +0.7, +1.7 (the +0.7 example) to use in this situation.

Just thinking a possible way to automate ettr when u have someone waiting for u.

Gary
 
jsrockit said:
Not to mention TIFF files from this thing are HUGE!
Click to expand...

This is why my default usage is medium raw and I only go to large raw when I c a shot that deserves it.

I find med raw image quality is still better than what I c from my xp1. Large raw is so good, no comment time... But that tiff16 from large raw eat up a lot of hd space.

Gary
 
noimmunity said:
Next up is another problem I just noticed: SENSOR SPOTS :eek::eek::eek:


SDIM0023-small by areality4all, on Flickr

Notching the exp comp down by 2 stops in post makes the spot much more obvious:


SDIM0023 (-2 exp)-small by areality4all, on Flickr

Here's another photo in which that spot appears:


SDIM0031-small by areality4all, on Flickr

And again at -2 exp comp in post to make it more visible:


SDIM0031 (-2 exp)-small by areality4all, on Flickr

Okay, so now that we have established the existence of the spot, what is really interesting is to notice that the position of the spot has moved slightly in the two images.

(The lens is crystal clear, covered by a UV filter, also crystal clear).

When the DP2M first started shipping last year, there were some sporadic reports of sensor spots.

But why would the spot move, especially given its relatively large size?
Click to expand...

Have u done the plain uniform same color shot to highlight the spot issue and report problem to Sigma?

Gary
 
I haven't seen green color shift with skies but I do often see desaturated region when an image with relatively large dynamic range is under exposed. The most underexposed region loses most of color info so it looks like I did selective desaturation in those areas. But when I raise the exposure, the colors do not come back.

Another issue with dp2m is that when shot with strong light (sun) in the images, halations of red spots appear in a line or sometimes multiple lines (see image below)
8661805196_175b1cc038_b.jpg
 
does the "Fringe correction" help to correct these issues?
seeems like i should avoid shooting into the sun and underexposure, ETTR for the win!
 
You must log in or register to reply here.
Back
Top Bottom