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03-27-2012, 01:37 PM   #1
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The K5 aspect ratio is not 1.5, and it can cause problems...

All,
This is sort of a beginner problem i suspect, but it caused me problems before i finally figured it out.

The native pixel length of K5 pictures is 4928 x 3264. Dividing the length by the width = 1.5098... or round it to 1.51 aspect. Doesn't sound like much of a problem does it? I read it a few times and always forgot it.

The first tip-off of this problem is when you import pictures into Lightroom and use their crop/straightening tool. One can pick several kinds of aspect ratios, and LR shows the K5 image as a "Custom" aspect. It doesn't show it as a 4x6 aspect. That's the first tipoff i didn't understand.

I've been printing larger canvas pictures lately from a remote factory and i'd get these messages as to whether I wanted to pay $5 for cropping my image or was it ok to leave the canvas 1/4" longer. I was printing 20"x30" and 24"x36" pictures at the time, so i called them and asked what the problem was. I thought it was something they were doing wrong. Then i thought that it was Lightroom that was doing something wrong. Then i discovered it was me, myself and I that were not correcting the issue to start with.

On a 20x30" canvas, the 1.51 ratio will cause the length to be 30.2". On a 24"x36" canvas, the 1.51 aspect ratio will cause the length to be 36.24" long. Canvas stretcher bars only come in whole length numbers, so a 1/4" increase in length will cause the border edge to look funny when you try to sell it retail. (doesn't take much to put off a buyer)

Once you know what the problem is, the fix is simple. In Lightroom, open up the crop tool and choose the 4x6 aspect crop ratio. The program will draw the crop box on your 1.51 ratio image - you click done and thats all there is to it.

I also do a lot of print ordering online with Costco. Occasionally i would get an icon indicating a need for a crop and it wasn't any kind of significant crop so i would do it with their online crop tool. I couldn't figure out why i was getting those messages until i understood more about the Sony Sensor in the K5.

I don't consider this to be any issue with the K5, i'd be surprised if the D7000 isn't the same way. I don't know if this affects other Pentax sensors. But if it does, its easy to fix with software once you recognize the problem.

It would be nice if there was a software option in the custom menu to do the 1.5 aspect crop with the firmware.

Hope this helps someone - took me too long to figure out myself


Last edited by philbaum; 03-27-2012 at 04:42 PM.
03-27-2012, 01:44 PM   #2
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Merci ... good info

Bonsoir philbaum,

Thanks. I just bought LR3 and will get LR 4 upgrade free ... "little" tips like this go a long way, especially someone like me who is venturing into unknown territory. A good "heads-up" call ... merci encore.

Salut, J Frog
03-27-2012, 01:51 PM   #3
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Post process is where you crop your images to the size you want. Where I have my canvases done they wrap the canvases so I have to format to 23 x 33. You often have to make compromises to make your picture print in the desired ratio. Taking pictures is not the same as preparation to print. We crop our pictures to 2:3, 3:4 5:7 or 4:5 depending on the print, in our editing software. The ratio of the sensor 1.5 doesn't refer to the crop ratio, it refers to how the sensor compares to the size of a full frame sensor, for calculating the effective length of the lens you are using. Hence a 100 mm full frame lens would be the equivalent of a 150 mm lens on a 1.5 crop sensor.

You should be able to select a 2:3 crop in your post processing software and crop accordingly.
03-27-2012, 02:26 PM   #4
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QuoteOriginally posted by normhead Quote
You should be able to select a 2:3 crop in your post processing software and crop accordingly.
+1 on this, or any other format you would like to print on or use as a screensaver.

03-27-2012, 02:31 PM   #5
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QuoteOriginally posted by normhead Quote
The ratio of the sensor 1.5 doesn't refer to the crop ratio, it refers to how the sensor compares to the size of a full frame sensor,
Well, my title was exactly correct - i referred to the aspect ratio, which is a photographic term referring to the ratio between the width and height of a picture or the sensor. I'm aware that it can be altered in pp. Maybe the confusion is over aspect ratio being listed as a product of a fraction, i.e. 1.51, rather than as a ratio of the width to height separated by a colon.

When one alters the aspect ratio by using a different ratio than the native ratio of the sensor, then that will solve the problem. In this case, i was using the whole image coming from the sensor.

coincidentally the K5 sensor crop factor relative to a 35mm camera is 1.5 which is nearly the same as the aspect ratio of 1.51 between the width and height. They are not related to each other.

Last edited by philbaum; 03-27-2012 at 04:40 PM.
03-27-2012, 02:46 PM   #6
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QuoteOriginally posted by philbaum Quote
coincidentally the K5 sensor crop factor relative to a 35mm camera is 1.5 which is nearly the same as the aspect ratio of 1.51 between the width and height. They are not related to each other.
There are more not related things in the world that match to each other. How many nonsens would you like in this thread?
03-27-2012, 02:50 PM   #7
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QuoteOriginally posted by RonHendriks1966 Quote
There are more not related things in the world that match to each other. How many nonsens would you like in this thread?
Just trying to respond to normhead who thought i was talking about sensor crop factor.
03-27-2012, 04:25 PM   #8
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I feel stupid that I never understood why my shots always was the wrong ratio for uploading standards.

03-27-2012, 04:35 PM   #9
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I only recently noticed this myself with my K-7, which is similar. Yes, we crop our images down to different aspect ratios depending on the desired print size, but I don't think it's unreasonable to express surprise that a sensor which is very clearly designed to match the standard 2:3 aspect ratio (for easy 4x6" prints) does not in fact actually match it, precisely.
03-27-2012, 04:51 PM   #10
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QuoteOriginally posted by VisualDarkness Quote
I feel stupid that I never understood why my shots always was the wrong ratio for uploading standards.
For the site you also have to resize to fit within 1024x1024 if you are starting a thread or 900 x 900 if you are contributing. It's not just the aspect ratio.

So there are two issues, one crop to the desired ratio.



Then resize to the desired size.

03-27-2012, 04:55 PM   #11
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I used to just put in the width and as I thought it was the correct ratio (3:2) I just expected "keep ratio" to be sufficient when resizing. I learned something new tonight.
03-27-2012, 05:52 PM   #12
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Good suggestion, thanks! I've been glazing over the 1.51 ratio as well.
03-27-2012, 06:46 PM   #13
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I shoot various digicams at various aspect ratios, mostly around 4:3 or 3:2. The image I see when I trip the shutter isn't necessarily what the sensor captures. Pictures that emerge from my laboratory after I've tortured and mutated them are not necessarily in the capture aspects. And any image I print is custom-cut to the exact size desired for printing, with margins as needed. That's the only way to control how the final picture looks.
03-27-2012, 06:57 PM   #14
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QuoteOriginally posted by RioRico Quote
I shoot various digicams at various aspect ratios, mostly around 4:3 or 3:2. The image I see when I trip the shutter isn't necessarily what the sensor captures. Pictures that emerge from my laboratory after I've tortured and mutated them are not necessarily in the capture aspects. And any image I print is custom-cut to the exact size desired for printing, with margins as needed. That's the only way to control how the final picture looks.
I don't do any printing as I am a homeless man couch surfing without walls of his own to decorate, however in the future when I have them I will probably want to throw some of my photos up. I have frequently mulled over the idea of custom margins on prints and then manually cutting down to maintain the aspect ratio of the image I produced, but I have to ask -- do you cut your own customs mattes as well to fit them?
03-27-2012, 11:04 PM   #15
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QuoteOriginally posted by v5planet Quote
I have frequently mulled over the idea of custom margins on prints and then manually cutting down to maintain the aspect ratio of the image I produced, but I have to ask -- do you cut your own customs mattes as well to fit them?
No I don't. For images I print and matte and frame and hang, I buy stock material, and crop and print the images to fit. If I were serious about this, I'd make a close friend of someone in a framing shop, eh?

Images and margins can be finessed to accommodate slightly variant aspects. Thus, say I have a 3:2 image (containing lots of white) and a 4:3 frame and matte. The entire image is important, so I can't crop or compress it. I may print the image with somewhat wide margins, with a very thin line halfway between the image and matte edges. That outline serves to transition between the two aspects.

Or I can just cheat. Print the image with no margins, and sandwich it between two sheets of acrylic so the image hangs in space. Some folks like those. There are other tricks. More later.

Last edited by RioRico; 03-27-2012 at 11:12 PM.
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