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Would these pass QC or fail due to CA?


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Hello,

 

I'm rather new to Alamy. I have some images of Darmouth in South Devon that i would like to upload but I'm not sure whether they would fail QC due to Chromatic Aberration.

I'm concerned that the boat masts and the backgrounds will fail.

 

I've uploaded a sample of the images that I am unsure of here:

 

http://s1324.photobucket.com/user/Matt_Ashmore/library/Alamy%20Questionable

 

Any thoughts are most welcome!

 

Best Regards,

Matt

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Hi Matt - I had a look, but for chromatic aberration we need to be able to magnify to 100% and I dont think I was able to with these images as they are. Hence cant give an opinion  :(

 

Kumar

 

ps. can you upload some 100% images ?

Edited by Doc
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Difficult to tell with some but the shot of Kingswear from what seems to be Bayards Cove (in f/ground) has some obvious CA in the houses top left - the contrast edges are quite red.

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Just had a look at a zoomed download and it's pretty awful, I'm afraid. The LR tool might fix it but you'd really have to like them to take the chance.

Any idea why it's so bad?

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Hi Matt - I had a look, but for chromatic aberration we need to be able to magnify to 100% and I dont think I was able to with these images as they are. Hence cant give an opinion  :(

 

Kumar

 

ps. can you upload some 100% images ?

 If you press the magnifying glass and then 'Save as" it saves as a 17mb jpg.

 

Michael

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  • Solution

Hi Matt,

Thanks for providing the images to look at.

 

In my opinion:

 

DSC_150 I think would fail for Soft & Lacking Definition plus a dust spot. (If these are the actual files you will submit and not heavily jpg compressed etc)

DSC_151 I think would fail for SaLD.

DSC_152 I think would fail for Chromatic Aberration and SaLD. There is too much CA in this one to be worth trying to deal with imho. Also a dust spot.

DSC_0154 I think would fail for CA and SaLD.

 

I'm sorry to be harsh but it's my honest view based on QC failures I had when starting out. The SaLD might be to do with how you've uploaded them to show us. The CA is definitely an issue. The dust spots are easy to deal with.

 

Michael

Edited by Armstrong
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Hi Matt,

 

I agree with Michael. All of them look a bit SoLD (Soft or Lacking Definition) to me with some quite significant red CA, especially on the left hand side, for example DSC_151 on the boat masts on the left, DSC_152 where the white chimney stack overlaps the dark roof.

 

I did't spot the dust though maybe I need new glasses? There's a bird in the sky of DSC_0150 that I'd probably clone out to avoid any possible confusion with dust. But try as I might I can't spot any dust in DSC_152.

 

There also seem to be some artifacts/noise along the skylines suggesting at some stage they may have been over-compressed or they're just jpgs straight from the camera? For best results shoot in raw and convert to jpg in LR / ACR.

 

I wouldn't submit any of these images to Alamy QC.

 

Mark

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Thank you for all of the replies. This was just the kind of feedback that I was hoping for.

 

They were taken quite a number of years ago with a Nikon D50 (so borderline camera) when I had less of an appreciation on how to properly use a DSLR (still learning now.. but know slightly more now).

I had feared that the CA would be too much and that they might be soft too.. but not having had too much experience of the Alamy QC process, I'm still 'getting a feel' for how far you can get away with these things (or not).

 

As much as I love the scenes myself, I wont be uploading these images.

 

Thanks again to all who commented.

 

Best Regards,

Matt

Edited by Matt Ashmore
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There's a dust bunny (more like a small elephant really) in the middle right about 15mm in diameter at 100%. It's in the same spot in all four images.

Are you sure you're working on a calibrated screen?

The colors look fine, but my guess is that the brightness level is a bit high.

Difficult to say though, it may just be your choice to have slightly dark sombre images of a clear and sunny place at sunset. ;-)

 

wim

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There's a dust bunny (more like a small elephant really) in the middle right about 15mm in diameter at 100%. It's in the same spot in all four images.

 

wim

 

Now I'm getting really worried. A dust "elephant" 15mm in diameter at 100%, and I still haven't spotted it. :(  Whereabouts is it?

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There's a dust bunny (more like a small elephant really) in the middle right about 15mm in diameter at 100%. It's in the same spot in all four images.

 

wim

 

Now I'm getting really worried. A dust "elephant" 15mm in diameter at 100%, and I still haven't spotted it. :(  Whereabouts is it?

 

Edited by Armstrong
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th_Alamy%20Upload%2024April2015%20DSC_01

 

Apologies for the double post.

 

When I am doing my checks for dust spots I duplicate the layer. Then equalize the new layer. I then highlight the background layer and remove any spots. Pressing 'cmd I' also helps.

 

I would guess that Alamy QC would have a similar action for quickly identifying any dust spots.

 

Michael

Edited by Armstrong
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Thank you for all of the replies. This was just the kind of feedback that I was hoping for.

 

They were taken quite a number of years ago with a Nikon D50 (so borderline camera) when I had less of an appreciation on how to properly use a DSLR (still learning now.. but know slightly more now).

I had feared that the CA would be too much and that they might be soft too.. but not having had too much experience of the Alamy QC process, I'm still 'getting a feel' for how far you can get away with these things (or not).

 

As much as I love the scenes myself, I wont be uploading these images.

 

Thanks again to all who commented.

 

Best Regards,

Matt

 

Matt,

 

I started off on Alamy with a D80. Looking back on the files from that camera now there is a clear difference between those and newer cameras. I recently went back into my archives to see if there was anything I'd like to process with the latest RAW processor. I found that the files simply couldn't handle much shadow recovery and any adjustments made the files quite noisy.

 

To tie in with what you said about them being images you really like...when I started to get sales it wasn't my faves that appeared. In fact about 50% of the time it was simpler ones that appeared. Technically competent but mostly not ones I'd hang on my wall. The common factor was that they all illustrated something specific. I can see images such as EMNJX3 selling for you.

 

Michael

Edited by Armstrong
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th_Alamy%20Upload%2024April2015%20DSC_01

 

Apologies for the double post.

 

When I am doing my checks for dust spots I duplicate the layer. Then equalize the new layer. I then highlight the background layer and remove any spots. Pressing 'cmd I' also helps.

 

I would guess that Alamy QC would have a similar action for quickly identifying any dust spots.

 

Michael

 

 

Thanks!

 

Ok, I selected just the sky in PSE, contracted the selection by 5 pixels, hit auto-levels and boom there it is! But I really struggle to see it in the original image. Sure it shouldn't be there, but would QC fail that?

 

The blob is quite diffuse I wonder if it's dust on one of the lens elements or oil on the sensor?

 

Luckily I rarely lenses now so dust is less of an issue, but having seen that I missed this one, I think I'll go and take a test shot of a clear sky and whack up the contrast.

Edited by M.Chapman
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th_Alamy%20Upload%2024April2015%20DSC_01

 

Apologies for the double post.

 

When I am doing my checks for dust spots I duplicate the layer. Then equalize the new layer. I then highlight the background layer and remove any spots. Pressing 'cmd I' also helps.

 

I would guess that Alamy QC would have a similar action for quickly identifying any dust spots.

 

Michael

 

Thanks!

 

Ok, I selected just the sky in PSE, contracted the selection by 5 pixels, hit auto-levels and boom there it is! But I really struggle to see it in the original image. Sure it shouldn't be there, but would QC fail that?

 

The blob is quite diffuse I wonder if it's dust on one of the lens elements or oil on the sensor?

 

Luckily I rarely lenses now so dust is less of an issue, but having seen that I missed this one, I think I'll go and take a test shot of a clear sky and whack up the contrast.

 

I would speculate that they would. The end use client might end up manipulating the image to create a certain mood or look. There's the risk that this could bring the dust spot to prominence. I would tend to err on the side of caution in that if it's there, it should be removed.

 

Michael

Edited by Armstrong
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th_Alamy%20Upload%2024April2015%20DSC_01

 

Apologies for the double post.

 

When I am doing my checks for dust spots I duplicate the layer. Then equalize the new layer. I then highlight the background layer and remove any spots. Pressing 'cmd I' also helps.

 

I would guess that Alamy QC would have a similar action for quickly identifying any dust spots.

 

Michael

 

 

Thanks!

 

Ok, I selected just the sky in PSE, contracted the selection by 5 pixels, hit auto-levels and boom there it is! But I really struggle to see it in the original image. Sure it shouldn't be there, but would QC fail that?

 

The blob is quite diffuse I wonder if it's dust on one of the lens elements or oil on the sensor?

 

Luckily I rarely lenses now so dust is less of an issue, but having seen that I missed this one, I think I'll go and take a test shot of a clear sky and whack up the contrast.

 

 

The problem is that we have no idea how the image will be used. If a client wants to make a cover with it, or a double spread with a text overlay, or anything that includes a darkened overlay, the dust will be very visible.

It would be ok if you would not be working for a client: if the only output is a print to hang on your wall, it's fine of course.

 

It's a simple dust bunny. Just a bit big.

Try it with a lens of the same focal length and at the same aperture to see how big a dust particle on the rear element must be to be noticed. Try the same for the front element. It will look totally different. It will mainly show up as a degradation of contrast. Unless it's an extreme wide angle, when it will be almost in focus on the front element at smaller apertures.

Oil would have a sort of a puddle appearance if it was this size. Oil from moving parts in the mirror box or shutter are usually much smaller. When Nikon had oil problems (D600) lots of images appeared online to show what they looked like. When you do the same search for Canon sensor oil, you'll see some of the puddles. While bigger than the Nikon oil spots, they're still quite small.

If dust is this big, it's very unusual to stick. It would be something that has dropped in while changing lenses. It could be anything form a rain drop (though that would look differently) to spit (same) or dander or dandruff (not uncommon). The usual particulates that float in the air are much smaller. But they can stick more easily. In the olden days you would have to look into the sun or a strong light against a black background to see them; now we have an app for that ;-)

 

wim

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th_Alamy%20Upload%2024April2015%20DSC_01

 

Apologies for the double post.

 

When I am doing my checks for dust spots I duplicate the layer. Then equalize the new layer. I then highlight the background layer and remove any spots. Pressing 'cmd I' also helps.

 

I would guess that Alamy QC would have a similar action for quickly identifying any dust spots.

 

Michael

Excellent and very useful tip thank you.

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Last time I checked there were about a quarter million articles online about checking for dust in Photoshop (in Lightroom there is a tool for that, but not in Photoshop).

Now there are a 100.000 more. Take your pick.

 

Mine: an action creating two adjustment layers one for Levels and one for Curves. I play with those for different areas in my image.

 

The average for a usual image of mine is about 100 to 400 dust spots that I have to remove. On both Canon Ds-s. Sony Nex a lot less. The Sony RX100-s totally zero because they're fixed lens pocket cameras.

With a longer lens and larger aperture, there are almost no dust spots visible. Only the really biggies appear. Those are visible to the naked eye, when looking at the sensor.

However with really wide angle lenses and small apertures, the thing quickly becomes a nightmare especially in nice blue skies.

Whoever cleans it, there's always dust, just in different places.

A professional cleaner in Denver once managed to hit the sensor (probably with a tweezer) and cause a permanent dust spot right in the middle in my older Ds. Because it is in the middle, I rarely have to clone it out.

He obviously did not use the excellent Nikon chopstick method of course, because he was a Canon man.

 

wim

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400! Ouch! I used to reckon I was badly off when iI had to do half-a-dozen on the A350.

With the A55 it's now very rare, which is odd because the shutter is open all the time, but there's a mirror bunging up the hole. Occasionally a bit of dust on it causes a very diffuse spot.

But I went from monthly wet cleans to twice a year.

That chopstick method looks a bit rough.

Edited by spacecadet
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My guess is that a mirror flapping around causes most of the dust. Probably sucking it in from the rear of the lenses. If then the shutter goes up and down a couple of times, like with HDR, all that ends up on the sensor. Why it all sticks to the sensor, I don't know. A fact is that the newer camera's are less prone to it. Do they heat up less, build up less static or have better coating?

 

I must admit I use no chopsticks either. Visible Dust Swabs usually are my weapon of choice.

 

wim

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I believe that the main reason for dust sticking to the sensor is static, which is discharged as part of the in-camera sensor cleaning process.

 

It would presumably be more of an issue with mirrorless cameras as when the lens is removed, the sensor is exposed (at least with a DSLR there is a mirror and shutter in the way.

 

It's for this reason that users of mirrorless cameras are advised to turn the camera off when changing lenses.

 

Unless that's just another urban myth (why are there no rural myths?)

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