85mm usm and 15-85mm IS usm lens

[An drew]

why was 15-55mm not enough

Of course not enough because it does not exist.

There actually is no need to get any new lens.

A friend once said I don't need a new lens/camera/tripod just like I don't a new hole in my head. Yeah, all you need is a pinhole.

 

[Anson]

The other problem with APS-C camera in such application is that with a smaller frame, you really cannot afford to crop your picture for better framing when your lens is not long enough.

With the current batch of APS-C camera from canon which offer 18MP, cropping should not be an issue. Unless you are really going for a A2 size print, most of the time a 4R to 5R is what most people print these days.

 

[New2digital]

Don't confuse fixed focal length (i.e. "prime") lens with fixed-focus lens
I used to own a very simple PnS which wasn't able to adjust focus (be it auto or manual) at all. I don't even know if such cameras still exist any more

Actually with a smaller sensor you get a higher pixel density, which gives you more megapixels from which to crop This is contrary to what you have stated.

Thank you for the correction, Yes I meant fixed focus Length and not fixed focus as in fixed at infinity as used in very cheap P&S cameras of old. In the contact I used the term, while not accurate, I do not think most readers got confused, Still it is better to be accurate if cannot be precise. I am thankful for the correction as it actually slip my mind.

Pixel density is a function of today's manufacturing technology and cost effectiveness in the processes If indeed a manufacture is able to get the pixel smaller for and actually applied to the APS Chip, there is no reason why that manufacturer will not apply the same ability to the FF chips too(here I am only addressing CMOS CHIPS since APS are CMOS). Thus we have FF chip in the 20+ mp while the APS chips hoover around the 16-18 mp. There is no truth that the APS chips has more pixel to spare for cropping as compared to FF chips. There is also the under utilization of the lens in APS cameras as compared to the FF camera. For this reason, I stopped serious photography for more than 10 years while waiting for the digital camera to go FF. I just got back to photography just a months or so ago. In fact I am still not back in the swing of things as yet. Anyway, photographic fundamentals never change even with the move to digital, just the image capturing media has changed and I think for the better as it is infinitely more flexible with digital media. There is no contradiction in my earlier statements.

All the same,thank you for sharing your thought.

 

[New2digital]

With the current batch of APS-C camera from canon which offer 18MP, cropping should not be an issue. Unless you are really going for a A2 size print, most of the time a 4R to 5R is what most people print these days.

This is true in general term. However, in the contact of this discussion, we are really referring to getting the best out of the camera and the lens thus 85mm verses the 15-85/17-55mm, else there is no discussion required nor the need for the TS to seek comments on which way to go. Just stay on his existing lens, save his money and let the software on his PC/Mac do the composition there-after. Very true, with 16 to 18 mp for 4/5R prints, There really is no need for this discussion. In fact for the past 10 odd years I only use very low pixel counts P&S consumer camera for all my holiday shots. Hell, I even rely on the "cameras" on my phones for quite many of these shots, which really is more than enough for Facebook purpose. If I want to see the wrinkles on the old man's face when he shouted for joy across the football field, then Yes, I am going to need a much better camera and especially the right lens than the iPhone camera.

I like to focus my discussion on the objective of the discussion itself to exact maximum from the discussion. Thank you.

 

[New2digital]

With the current batch of APS-C camera from canon which offer 18MP, cropping should not be an issue. Unless you are really going for a A2 size print, most of the time a 4R to 5R is what most people print these days.

There is also the issue of how much of these 18 mp is capturing the subject proper and this is where the lens comes into play. Surely a subject captured with a 85mm lens which fill the frame, yields better result than the 17-55mm lens at the same distance. It's all about relativity.

 

[ZerocoolAstra]

Pixel density is a function of today's manufacturing technology and cost effectiveness in the processes If indeed a manufacture is able to get the pixel smaller for and actually applied to the APS Chip, there is no reason why that manufacturer will not apply the same ability to the FF chips too(here I am only addressing CMOS CHIPS since APS are CMOS). Thus we have FF chip in the 20+ mp while the APS chips hoover around the 16-18 mp. There is no truth that the APS chips has more pixel to spare for cropping as compared to FF chips. There is also the under utilization of the lens in APS cameras as compared to the FF camera.

well, a FF sensor is at least double the area of an APS-C sensor, and the 5DmkII doesn't have twice the megapixel count of the 7D for example. So pixel density in APS-C is usually higher.
If covering a football match with tele lens and 7D, the output image is "tighter" than when using a FF body. Thus you may need to crop less to get a tight shot of that player in action.
In this instance, the APS-C sensor can be 'advantageous'