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Old Dec 25, 2007, 7:58 PM   #1
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Although not intrinsically a "Pentax" question, the pentax crowd gives good feedback, so figured I'd give it a try.

My wife and I had a 6x6 and a 4x4 print made from b&w digital photos (both came from same source photo). The size differences were only obtained by changing the dpi without resampling. The 4x4 had a dpi of about 350, and the 6x6 of about 250. When printed at the local Ritz (their printing capability is considered to be quite good), the 6x6 is clearly overexposed and the 4x4 is right on.

I wanted to ask if lower dpi is known to produce lighter prints. On the computer screen both sizes look great and of identical brightness/contrast. It kinda makes sense that if less dots are printed per inch, then the darkness of the photo would be less, but I didn't expect the result I got.


I'm using a 6 MP ist DS here. I think default dpi of photos is 72 - is there a way to change that (on a default basis)?

Thanks!
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Old Dec 26, 2007, 2:51 AM   #2
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MaybeRitz screwed up? I do not see how dpi has anything to do with causing over exposed pics in any way.

Tony
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Old Dec 26, 2007, 7:51 AM   #3
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i agree with tony. sounds like ritz or the paper. i print at 240-300 all the time and see no difference..
72dpi is native for the pentax cams as far as i can tell you can't change that. in PS you can choose to resize without resampling and end up with an 8x12'' at 300 dpi or there abouts. out of the cam at 72dpi the image is around 4x5feet.. i know there are cams out there that come out of the cam at 300 but what difference does it make..

roy
edit: have you tried printing them yourself??
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Old Dec 26, 2007, 10:19 AM   #4
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I agree with the rest I don't see how DPI could have had any effect on the exposure. Since most of these commerical printing systems do some "automatic image improvements" to try and at the very least make the image look correct for its system it is more likely that either their system hickuped at a bad time or something in the image like a large around of dark colors caused it to over expose the image.

Maybe if you could post both images (please indicate which is which) we might be able to help more.

Robert
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Old Dec 26, 2007, 10:21 AM   #5
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One more thing. 250 dpi is not low resolution. Anything between 200 and 400 is about right. Above 400 is ultra high resolution. Between 100 and 199 is medium resolution, below 100 is low resolution. 200 to 400 is normal printing resolution. 400 hundred fits because of how some people calculate the DPI needed based on the resolution and number of inks their printer has. But, in general these are accurate.

Robert
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Old Dec 26, 2007, 10:31 AM   #6
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Changing the default 72 dpi to something like 300 dpi is not a big deal; I just never print anything at 72 dpi so would prefer a more reasonable default.

Regarding Ritz's potential for error, I don't own a photo printer, so can't test myself. I have no idea how knowledgable or competent the print people are, but that in general they tend to put a lot of trust into big expensive pieces of equipment mostly because they are big and expensive. In any case, I'd like to have a good idea of what could be wrong on their side before I make any kind of crusade. With that thought, I've never done any dpi comparison to see if pictures printed with differing dpi's exhibit differing characteristics other than resolution.


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Old Dec 26, 2007, 1:44 PM   #7
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Most photo printing places go full automatic, they very seldom have someone standing there tweaking their system to produce the best possible photo. Most times the fully automated systems does a good job. But, it doesn't do that with every photo, nothing can or does.

If you want the best prints and want someone standing their making small adjustments to get the best prints then you need to find a professional lab and be prepared to pay the extra cost of such a service. This is way printing at home is better in my opinion.

As a side note with most labs if you have a photo that didn't turn out like it should have (their system over or under exposed it, or there is some other problem) if you tell them they will usually correct it and make you another print at no cost. But you really need to do this before you leave. Which means checking your order before you leave.

Honestly I don't know why getting good color and prints at home is so hard. It seems to me that by now everyone should have come together to create a system that even a brain dead consumer could use to get spot on prints from their own printers without all of the hoop jumping. sRGB was supposed to do this, but it hasn't even come close. The monitor, video card, OS, photo editing software, printer, ink and paper companies really need to team up and get this done.

By my way of thinking if you stick with name brands then when you install a monitor, video card, printer, etc. the OS should say ok I have this, this and this I need to set this, this and this and then all that you have to do for perfect prints is select the proper paper in the printer driver and your done. You should have't fool with profiling, profiles, and the link. Everything some just been recognized and auto configured for perfect prints. I think the technology is there for this. We just need to get the manufacturers to work together. Especially given the high cost or paper and ink, it really should be a simple process by now.

Robert
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Old Dec 26, 2007, 3:58 PM   #8
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I use Costco and their online setup says nothing under 300dpi, I can't print photos at home for that price and if they screw up then they print it free again.
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Old Dec 26, 2007, 4:06 PM   #9
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Automated machinery is only as good as the person programming and running it...Don't know their setup but they should be able to do better than that...Just a matter of changing a parameter or setting!.

Dawg
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Old Dec 26, 2007, 5:13 PM   #10
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Basically, the woman there at the time knew nothing about their printing capabilities beyond that it was likely to be my fault if something is wrong. In general I find that if I print something as is from the camera, it comes out ok on their system. But, if I do any contrast or brightness adjustments, it's a gamble what it will look like on their system. In fact, that 6x6 that turned out overblown was a second attempt - the previous 6x6 attempt had been brightened in photoshop which also resulted in an overblown print. For the second attempt I did no brightening, yet the print came out looking exactly the same. This led me to think it might be a dpi issure, but it sounds more like their system is asserting some kind of "autobalancing" routine when it prints.
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