For my fast primes i.e. 30mm 1.4, 50mm 1.4, it was essential. DoF is so razor thin that autofocus accuracy is the case of achieving focus or not. The benefits of AF fine tune are immediately noticable. With my consumer 18-200 3.5-5.6, the DoF is considerably larger, and this didn't benefit from any changes to the AF. Pixel peeping that I didn't notice with the D200 or even D70? I don't think so - I've had a 18-70 that I was never really satisfied with on the D70, and my 50/1.4 and some other lenses I've used with the D200 have never been 100% sharp (not due to DoF either). The lenses have consistently performed (well or poorly), only on the D300 have I been able to adjust this if necessary.
Canon and Nikon Microadjustment
- Thread starter thegary
- Start date
Thank you for the post, its a good read. The pictures show what i suspected as well. Seems to be as we get higher in MP we can expect this.
Its good that i see that some NIKON users have posted and they are adjusting for the same thing. I was starting to think this was a CANON problem. I suppose its time to retrain my way of thinking with the new cameras that are coming out. Some setup will be required to get the most oout of them.
It would be good IMO that Canon, could put up some sort of post or even a product with their cameras to help bring the camera to its best possible setup. This would likely reduce the amount of tech support they have to do, and make us camera users happier with the product.
Thanks again everyone.
Gary
Its good that i see that some NIKON users have posted and they are adjusting for the same thing. I was starting to think this was a CANON problem. I suppose its time to retrain my way of thinking with the new cameras that are coming out. Some setup will be required to get the most oout of them.
It would be good IMO that Canon, could put up some sort of post or even a product with their cameras to help bring the camera to its best possible setup. This would likely reduce the amount of tech support they have to do, and make us camera users happier with the product.
Thanks again everyone.
Gary
Many of the lenses in use today date back to the film era when people shot 35mm film and might typically print at up to 12x8. The accuracy of the AF systems between camera body and lens served that era perfectly well. Of course, in the film days there was no such thing as pixel peeping and viewing 100% crops and then complaining about image (pixel!) softness.
Even when digital SLRs came onto the scene the low pixel density meant that the camera didn't really have the resolution to make AF performance too critical. A 6 megapixel DSLR file viewed at 100% would display at a virtual size of approx 27"x18" when viewed on my laptop screen. That is a big step up in magnification from a 35mm negative going to a 12" print. In fact it is an enlargement 3.6X greater, assuming the DSLR in question has an APS-C sensor, and far more likely to reveal problems with AF accuracy, but the tools were not available to us mere mortals to improve things, even if we needed to.
Now that we have APS-C cameras with pixel counts of 15MP and 18MP, viewing those images at 100% simply makes the cracks too obvious to ignore. Perhaps on a slow, possibly soft, consumer zoom lens the DOF is large enough to make hyper-accurate focusing less important, but with some lenses and shooting styles you will need mm perfect focusing.
A 7D file, viewed at 100% on my laptop, is equivalent to a virtual image of 39"x26". If those pixels are to add an advantage then the captures have to be focused accurately. What was acceptable for film, and the D30, and even the 30D, may no longer be acceptable for a 50D or 7D. The AF needs to be more accurate, but the lenses are still (mostly) the same old lens designs of yesteryear. It is therefore no longer the case that mere engineering tolerances will satisfy the most meticulous pixel peeper. The manufacturers have now given us a tool so that we can tighten the tolerances for ourselves, in our own homes.
Some may say that AF microadjustent is a cop out. Perhaps it is. However, I think it is a way for the manufacturers to manage manufacturing costs down to an acceptable level, while still allowing the most fastidious photographers to squeeze the maximum performance from their gear.
As an example, here's a shot I took today with my 7D and 100-400. (apologies for the IQ - the website that hosts the file has resized it)...
If we zoom in to 100% to take a look at the DOF we see that it is probably no more than 2-3mm....
If my AF was not accurate to the mm then a shot like this would fall short of the best that one would wish for. If my AF had been off by more than 1mm, or 2mm at the most, this shot would have been ruined. As it happens, I have checked the focusing of this lens and it has not needed adjustment, but I do have other body/lens combinations that do benefit from some tweaking.
If you want to realise the maximum potential of your high resolution camera, whether a 50D, 7D or something else, it is worth making sure your focusing is as accurate as possible, and not simply "close".
HoppyUK
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Many of the lenses in use today date back to the film era when people shot 35mm film and might typically print at up to 12x8. The accuracy of the AF systems between camera body and lens served that era perfectly well. Of course, in the film days there was no such thing as pixel peeping and viewing 100% crops and then complaining about image (pixel!) softness.
Even when digital SLRs came onto the scene the low pixel density meant that the camera didn't really have the resolution to make AF performance too critical. A 6 megapixel DSLR file viewed at 100% would display at a virtual size of almost 24"x16" when viewed on my laptop screen. That is a big step up in magnification from a 35mm negative going to a 12" print. In fact it is an enlargement ~3X greater, assuming the DSLR in question has an APS-C sensor, and far more likely to reveal problems with AF accuracy, but the tools were not available to us mere mortals to improve things, even if we needed to.
Now that we have APS-C cameras with pixel counts of 15MP and 18MP, viewing those images at 100% simply makes the cracks too obvious to ignore. Perhaps on a slow, possibly soft, consumer zoom lens the DOF is large enough to make hyper-accurate focusing less important, but with some lenses and shooting styles you will need mm perfect focusing.
A 7D file, viewed at 100% on my laptop, is equivalent to a virtual image of 39"x26". If those pixels are to add an advantage then the captures have to be focused accurately. What was acceptable for film, and the D30, and even the 30D, may no longer be acceptable for a 50D or 7D. The AF needs to be more accurate, but the lenses are still (mostly) the same old lens designs of yesteryear. It is therefore no longer the case that mere engineering tolerances will satisfy the most meticulous pixel peeper. The manufacturers have now given us a tool so that we can tighten the tolerances for ourselves, in our own homes.
Some may say that AF microadjustent is a cop out. Perhaps it is. However, I think it is a way for the manufacturers to manage manufacturing costs down to an acceptable level, while still allowing the most fastidious photographers to squeeze the maximum performance from their gear.
As an example, here's a shot I took today with my 7D and 100-400. (apologies for the IQ - the website that hosts the file has resized it)...
If we zoom in to 100% to take a look at the DOF we see that it is probably no more than 2-3mm....
If my AF was not accurate to the mm then a shot like this would fall short of the best that one would wish for. If my AF had been off by more than 1mm, or 2mm at the most, this shot would have been ruined. As it happens, I have checked the focusing of this lens and it has not needed adjustment, but I do have other body/lens combinations that do benefit from some tweaking.
If you want to realise the maximum potential of your high resolution camera, whether a 50D, 7D or something else, it is worth making sure your focusing is as accurate as possible, and not simply "close".
I think this issue is only indirectly related to pixel count. If the image above was shot on a 6mp camera (or high quality film) and enlarged to the same phyisical dimensions - ie to 39in wide and not just 100% pixels - the shallowness of the DoF and need for perfect focus accuracy would still be evident, even if it was not so clear.
The whole concept of DoF is related to viewing a standard sized print at 'normal' distance - from memory that is typically a 10in print print viewed from 12in. From this, the circle of confusion is derived as the smallest point that can be discerned by the human eye, and the formula is set.
When you then change the print size and viewing distance substantially, as is the case with pixel peeping, then the parameters for acceptable DoF - as used by manufacturers - no longer apply.
You could say that Canon has been hoist by its own petard in giving us cameras that can stretch the old rules so far, and so easily, that they leave us wanting. It would be interesting to see how a carefully micro-adjusted zoom performs a) at different focal lengths, b) at different focusing distances, and c) particularly if it is consistently accurate and can hit the target every time, first time, whether or not it is coming at it from closer or further away.