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11-09-2018, 09:26 AM   #16
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QuoteOriginally posted by philbaum Quote
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
For the benefit of new readers to this thread - The sensor size of a K5 in mm is 23.4 x 15.6...that's an aspect ratio of 3:2 EXACTLY. However, that sensor has 16.3 effective MP, but only 4928 along the 23.4mm side and 3264 along the 15.6mm side are used to create the image - that's 16,084992 pixels in total in an image (less than the 16.3MP of the whole sensor) giving an aspect ratio of 3:2 APPROX. Anyone trying to print to an exact ratio of 3:2 as in 30" x 20" or 36" x 24" prints with the whole image from this sensor is going to be disappointed with either space or cutting off occurring. Crop the image to the exact 3:2 ratio if you don't want either occurring.

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