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What do I lose if I do not shoot at maximum res? or the "superfine" setting? What are the disadvantages?

I would like to learn how digital cameras save in lower resolutions jpegs. Is the extra card-to-computer uploading time, space, and other hardware requirements all for naught when I will rarely crop pics and will never print larger than 8x10.

Also, does the answer vary depending on the sensor type or technology, the camera brand or model, or the subject being photographed?

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1  
Can you add information about your specific camera gear? Answers to some of the questions you have asked are dependent upon the gear, such as what its maximum megapixel rating is. It would also be helpful to know whether you only care about JPEG (for which those settings apply), or RAW (for which those settings do nothing.) –  jrista Sep 5 '11 at 18:23
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I don't think this question needs to be narrowed to specific gear to be answered in a useful, general way. –  mattdm Sep 5 '11 at 20:32

2 Answers 2

up vote 5 down vote accepted

In order to preserve maximum details and future editabiliy, it is best to save your images in RAW format, if your camera supports that. That said, it is generally far more demanding in terms of memory per image requirements, hence can limit your max number of images.

For JPEGs, there are generally two factors that determine the image quality (IQ). The first one is resolution. Obviously, the higher the resolution, the more details can be captured in your image. That said, you mentioned uncropped 8x10 prints max. A standard lab printer prints at around 300dpi. This translates to 2400x3000 pixels, or ~8 Mpix. If this is your max output format, then you can reduce the capture resolution to around that number (*).

The second factor is the quality, or compression, which is determined by the lossy part of the JPEG compressor. The compressor, generally, is throwing away the information of the higher frequencies in the image. Considering this, you can judge by your scene - if it is a scene comprised of tiny/fine details (e.g., a tree/grass, head-hair, etc.) you may want to keep quality at superfine.

Otherwise (shooting you car, for example, or other relatively smooth objects) you can lower the quality to save space.

(*) Note that when doing post-processing work that includes rotation or other pixel-destructive actions, having more pixels to work with will give you better final output.

Update in response to OP's commet:

Well, there are a few factors here. When dealing with this matter, I assume the consideration of technologies of similar age. A new sensor will most probably outperform an old sensor with a higher resolution. As the sensels shrink, their noise sensitivity increases up to the point that image details are lost in the sea of noise at the pixel level*. Thus, from some point increasing the resolution becomes meaningless. But, newer sensors have better noise immunity at the pixel level.

Different brands and models use some variations on sensor technology. The types I am aware of are standard CMOS, CCD and backside-illuminated CMOS. CCD and CMOS are comparable in noise performance these days. BSI is considered a newer technology which increases the amount of light gathered by the sensel, hence its noise immunity. In summary, there may be a difference in actual resolution between models but for same technology, it will increase your captured resolution (see next paragraph).

Remember that a sensor is not just the silicon piece but also a stack of filters and microlenses. One of the filters is a low-pass (anti-aliasing) filter that cuts the image's high frequencies before it reaches the sensels. This alone will suggest that the optical/analog image itself is more detailed in a higher res sensor.

Another point that affects actual resolution is the resolving power of the lens. Nowadays, most models have sensors that have outreached the resolving power of most lenses (absolutely definitely when you talk about high MP compacts or smartphones). This means that the benefit in increasing res is marginal, but it is there. @Matt Grum explained in on of his posts (I'll try to find it later) that the captured image is the convolution of the lens image (signal) and the sensor sampling function. As such, there will always be some improvement with increasing res, but it is questionable if you can take advantage on that.

As for the subject being captured - obviously (really, this time) if your subject has no details, then I don't see how increasing the resolution will improve the final image (digital interpolation will work just as well). I touched this point in the first part of the answer.

To sum-up: technology, as applied to different models even among a single manufacturer's line, can affect the resolving power of the sensor. When comparing same technology, one can show that increasing resolution does increase the amount of details up to the noise floor of the sensel. How detailed your subject is will definitely affect how detailed your image is.

Resolution alone is not the only player in the game, and when choosing a camera one needs to consider all the other parameters (lens, filters, processor, etc). Your question intent seems to be the choice of settings in the context of a given camera, which is what my original answer addressed.

Update II: Here's Matt's answer: Do megapixels matter with modern sensor technology?

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+1. One particular case where you want the best-quality JPEG level is when you have red tree leaves against blue sky. The combination of detail and high contrast across color channels is bad news for the JPEG algorithm. It'd be nice if cameras would automatically choose an appropriate level adaptively, but to my knowledge none do. –  mattdm Sep 5 '11 at 20:28
    
@ysap: "Obviously, the higher the resolution, the more details can be captured in your image." Presumptions have bitten me in the ass in the past, so let me ask you: Are you 100% positive of this? Is this true regardless of the sensor type or technology, the camera brand or model, or the subject being photographed? –  William C Sep 7 '11 at 3:44
    
@William C: As long as the sensor stays the same, downscaling the image can't increase the amount of details, only leave them unaffected or lose them. If you compare two sensors of same physical size and different resolution, then your point might stand a chance, but in this case the question is about what data to store and how after the image has been read from sensor. –  Zds Sep 7 '11 at 14:11
    
@ysap: So, to sum up: In order to preserve maximum details and future editability, shoot JPEGs in superfine, maximum resolution. However, nowadays, the amount of details gained in increasing res depends on the resolving power of your given camera's lenses (and obviously if your subject has details at all). Correct? –  William C Sep 9 '11 at 2:36
    
The 1st part is true if your camera can't store RAW files. Then, the resolving power of the lens is one of the factors for the resolving power of the camera. If your sensor has higher resolution than the lens, then increasing the sensor res will give you some more details, but the difference will diminish fast as you keep increasing the resolution. From some point you will have no effective gain. –  ysap Sep 9 '11 at 14:02

If shooting JPEG (and not raw), I would always use the maximum resolution and quality. Even at the highest settings the size of the resulting JPEGs is usually negligible compared to sizes of memory cards and hard drives.

If you really have so many JPEGs it's hard to find space for all of them, like tens of thousands, you might want to delete the ones you are not going to look at anyway, instead of reducing the quality for all images. Because no one really watches through 10k images very often.

With space out of the equation, storing speed might be a real issue. If you have really slow camera, compressing the image to JPEG and writing it to memory card can take some seconds. How much of this time you could save by storing in worse quality, that I don't know.

If moving images from camera to PC is a bottleneck, try getting a card reader from some memory card manufacturer. In my experience any card reader is miles and leaps faster to move images than compact cameras or entry-level DSLRs, and the readers from memory manufacturers are often engineered to make their (fast) cards justice. If you don't have CF cameras, you can use thumb-sized reader that supports SD/MMC family making size of the reader a non-issue.

On memory cards, with current size/money ratios actually "how many images I'm willing to lose at once" plays nowadays bigger role to me personally than "how many images my card can hold". I still use 8GB cards on my DSLR because of this - 8GB cards can hold 700 raws from my 450D, which is already very many, if I think of it in terms of how much I lose when the card gets stolen/breaks. Because any storage media will break eventually, and memory cards are even more likely to do that during their useful lifespan than hard drives, because they are inexpensive and lack redundancy of NAND flash compared to SSD drives.

The reliability is deducted from SSD drives being approximately as reliable as hard drives and SSD:s, unlike memory cards, have handful of individual NAND flash chips, so if one of the chips starts to fail, controller can reassign pages from it to the working units. Obviously to reassign gracefully, the faulty chip needs to show early signs of failure to the controller, but recovering from some failures is better than recovering from none.

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+1 for suggesting to filter out bad images from your 10K library. –  ysap Sep 9 '11 at 14:05
    
Do you have reference to support the last statement regarding flash cards reliability? –  ysap Sep 9 '11 at 14:07
    
Added sources now. –  Zds Sep 9 '11 at 14:25

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