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FORUMS Post Processing, Marketing & Presenting Photos RAW, Post Processing & Printing 
Thread started 08 Apr 2014 (Tuesday) 22:52
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Bet detail after an 'image crop'

 
monkey44
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Apr 08, 2014 22:52 |  #1

I'm not very tech-smart, started with film years ago, and the tech stuff sometimes eludes me as I have limited background in it.

SO, leads me to this question:

When I capture an image, and crop and enlarge, it loses some degree of detail, or becomes 'fuzzy' after a certain point. But, I'm not sure if it's something I do, or don't do, that loses the detail.

So, wonder if there is a step I'm missing that "compresses the image" into a more "compact" size, and then when we crop and enlarge, we gain some detail in the image "AND KEEP IT" as the compressed image enlarges again. But I think I'm asking this the wrong way, because compressing is not really the term for what I mean.

Not sure I'm explaining this exactly. Most of the time, I can enlarge as much as I want in any image (I shoot RAW with 5DM3 and 7D) ... so the detail is there generally. But, sometimes, even enlarging a half-crop and it looks like half the photons, or whatever creates the dots (pixels) seem to disappear. Not on all shots, just on some - and the shots look similar upon first examination -- only after enlarging does the lack of detail appear.

I always shoot at the largest size image - and get some very clear detail in my images. But it's the process of enlarging that puzzles me -- yes, I can get some large prints (easily 13x19 - or much larger) with perfect clarity, but some crops seem less able to get the size I'd like to see.

One other comment: It appears to me that the faster SS and larger aperture opening creates less detail overall. But, when one compares SS and AV, there exists a relationship between them, obviously, that allows less light and more light to offset the changes in SS or AV ... so, based on that (and skipping push-stops for now) that image should give a similar result in detail. So, I'm a little puzzled with this detail issue.

Any comments? And no, at this time, can't post a photo example, my site is down, and rebuilding.




  
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tzalman
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Apr 09, 2014 02:32 |  #2

Fifty years ago I made a dumb mistake. On an impulse I bought an Olympus Pen F half frame camera that exposed only half the amount of film as a full frame 35 mm camera, although I knew perfectly well that in photography size matters and bigger is better because prints are enlargements and the more you enlarge the more you smear the detail over a bigger area and blur it. You also make the film grain bigger and more visible. That camera sat in the closet for ten years until I gave it to my son. The 7D has 18 million pixels on a 15x22.5 mm. sensor. Crop out half the picture and it's like you have a camera with a 11x15 sensor with 9 MP. That's 0.4 x 0.6 inches. An 8x12 print is a 20 times enlargement, a 12x18 is 30X. The detail resolved by the lens is spread and blurred. Then there is an added factor in digital photography - pixels. The 7D has nearly 6000 pixels per inch on the sensor. Enlarge the image 30x and you have only 200 ppi. That's not enough for a printer, which needs at least 300 ppi, so the computer invents another 100 pixels per inch, 10,000 pixels per square inch. The quality of the computer's guesses about what color and tone the "phony" pixels should be determines if they blend in seamlessly or degrade the image. Obviously, the more the image is computer generated and the less it comes from a good quality lens, properly focused, the more degradation there is. The best thing you can do to improve the image is to get closer and crop less.

About your second point; lenses work best in the middle of their aperture range. Unless you have an expensive top of the line lens, having to use more of the glass surfaces at wide apertures means poorer performance and at the small apertures the bending of light going through a small hole called diffraction reduces image quality.


Elie / אלי

  
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monkey44
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Apr 09, 2014 09:51 |  #3

Yes, I pretty much understand your idea here, and the math. I shoot with all "L" glass, a 24-105 IS, a 70-200 f/4 IS, and 100-400 L IS primary lenses on the 5DM3 and 7D ...

My issue is: Sometimes, the image can enlarge and show amazing detail, and sometimes it does not, when I use the same settings (basically) and similar light in the scene. I'm thinking this "loss of detail" happens in the processing, that I miss or forget or set something I shouldn't. It's been a puzzle for me quite awhile. Sometimes, I'll be 150' or even 300' off a subject, and nail it so well the eye even pops out after a 4:1 crop or 6:1 crop even - sometimes, the 2:1 crop loses detail.

Same cameras, same lenses, same photographer - and I've been doing this a long time ... so, it bumps me into thinking I'm missing some simple thing in either the set-up or the processing when it happens. But my tech knowledge is a bit weak -- folks tell me to learn it (digital), yeah, OK, but that an awful lot of learning in a trade I have little interest in,and it changes so frequently. I know, I know, it's become part of the image world.

But, I want to continue getting my shots in the camera, with camera skills, not paint a picture with a digital program like many do today. It's just my choice ... and my challenge. But if the digital process is defeating it, then I need to add something. I was thinking we could compress or duplicate the 'dots' so we can enlarge and still maintain detail and sharpness -- but, am now thinking that was a mistake, and we can't in the real world images.

And, getting closer, yes as often as practical. Not always practical in the field, where my primary target is wildlife in the back-country. Much as I've tried over the years, can't get those little devils to pose ... :) Thanks for the info ... B




  
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maverick75
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Apr 09, 2014 12:20 |  #4

Compose through the viewfinder so you won't have to crop later on.

Cropping is my absolute last resort, 99% of the time I get it right the first time.


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tonylong
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Apr 09, 2014 18:19 |  #5

You know, maybe if you could show us some stuff:

You could post sample images, on that shows this problem and one that doesn't, post both the uncropped image (sized for the Web) and then a crop that clearly shows the problem.

You could also upload a Raw file of a pic that shows the problem.

But first, I'd suggest that you look at this thread and do the testing that starts in the second post:

https://photography-on-the.net/forum/showthre​ad.php?t=857871


Tony
Two Canon cameras (5DC, 30D), three Canon lenses (24-105, 100-400, 100mm macro)
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digital ­ paradise
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Apr 09, 2014 18:38 |  #6

monkey44 wrote in post #16821168 (external link)
Yes, I pretty much understand your idea here, and the math. I shoot with all "L" glass, a 24-105 IS, a 70-200 f/4 IS, and 100-400 L IS primary lenses on the 5DM3 and 7D ...

My issue is: Sometimes, the image can enlarge and show amazing detail, and sometimes it does not, when I use the same settings (basically) and similar light in the scene. I'm thinking this "loss of detail" happens in the processing, that I miss or forget or set something I shouldn't. It's been a puzzle for me quite awhile. Sometimes, I'll be 150' or even 300' off a subject, and nail it so well the eye even pops out after a 4:1 crop or 6:1 crop even - sometimes, the 2:1 crop loses detail.

Same cameras, same lenses, same photographer - and I've been doing this a long time ... so, it bumps me into thinking I'm missing some simple thing in either the set-up or the processing when it happens. But my tech knowledge is a bit weak -- folks tell me to learn it (digital), yeah, OK, but that an awful lot of learning in a trade I have little interest in,and it changes so frequently. I know, I know, it's become part of the image world.

But, I want to continue getting my shots in the camera, with camera skills, not paint a picture with a digital program like many do today. It's just my choice ... and my challenge. But if the digital process is defeating it, then I need to add something. I was thinking we could compress or duplicate the 'dots' so we can enlarge and still maintain detail and sharpness -- but, am now thinking that was a mistake, and we can't in the real world images.

And, getting closer, yes as often as practical. Not always practical in the field, where my primary target is wildlife in the back-country. Much as I've tried over the years, can't get those little devils to pose ... :) Thanks for the info ... B

I use a sharpening and resizing method (always down) that allows me to feather back the sharpening at the and and I have found no 2 images are alike. So it all depends on how much you crop and upsize.

Here is a video that may help you with the enlarging part.

http://www.youtube.com …4mV3NsLmXw&feat​ure=relmfu (external link)


Image Editing OK

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Bet detail after an 'image crop'
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