SD14 vs SD15 image quality ?

Started 11 months ago | Discussions
John Brubaker
Regular MemberPosts: 388
Like?
SD14 vs SD15 image quality ?
11 months ago

Is there a significant difference in image quality between these 2, or did Sigma just update the features and speed of the camera body?  thanks ---john.

Sigma SD14 Sigma SD15
If you believe there are incorrect tags, please send us this post using our feedback form.
mike earussi
Veteran MemberPosts: 5,014
Like?
Re: SD14 vs SD15 image quality ?
In reply to John Brubaker, 11 months ago

Color is more accurate on the SD15 and the DR is greater on the SD14, especially the highlights. Also the SD14's focusing screen in the bodies I had were not aligned properly so manual focus was not accurate. Having owned both I really like the increased operative ability of the SD15 but I do miss having the greater DR of the SD14.

Reply   Reply with quote   Complain
John Brubaker
Regular MemberPosts: 388
Like?
Re: SD14 vs SD15 image quality ?
In reply to mike earussi, 11 months ago

mike earussi wrote:

Color is more accurate on the SD15 and the DR is greater on the SD14, especially the highlights. Also the SD14's focusing screen in the bodies I had were not aligned properly so manual focus was not accurate. Having owned both I really like the increased operative ability of the SD15 but I do miss having the greater DR of the SD14.

Was the sensor changed from SD14 to 15?  I'm surprised that SD15 would be inferior to the earlier body in any way?

Reply   Reply with quote   Complain
Peter A. Stavrakoglou
Veteran MemberPosts: 7,442Gear list
Like?
Re: SD14 vs SD15 image quality ?
In reply to John Brubaker, 11 months ago

It's the same sensor in both cameras.  I use the SD15 now.  I don't miss the lock-ups on my SD14 or the green cast to images.  I was able to correct the green cast easily but I do like not having to deal with that with my SD15.

-- hide signature --

My humble photo gallery: http://www.pete-the-greek.com

 Peter A. Stavrakoglou's gear list:Peter A. Stavrakoglou's gear list
Fujifilm X-S1 Panasonic Lumix DMC-FZ200 Sigma SD15 Canon EOS 7D Sigma SD1 Merrill +16 more
Reply   Reply with quote   Complain
mike earussi
Veteran MemberPosts: 5,014
Like?
Re: SD14 vs SD15 image quality ?
In reply to John Brubaker, 11 months ago

John Brubaker wrote:

mike earussi wrote:

Color is more accurate on the SD15 and the DR is greater on the SD14, especially the highlights. Also the SD14's focusing screen in the bodies I had were not aligned properly so manual focus was not accurate. Having owned both I really like the increased operative ability of the SD15 but I do miss having the greater DR of the SD14.

Was the sensor changed from SD14 to 15? I'm surprised that SD15 would be inferior to the earlier body in any way?

Sigma added some sort of preamp called an "Analog Front End" to the processing pipeline in an attempt to decrease the noise at higher ISOs, the byproduct of which was to decrease the DR by about one stop. It may have worked to some extent, but as a noise reducer but it wasn't worth the tradeoff of the loss of DR. I believe the DP1s and x and the DP2s also have it. Consequently, the SD1M and DPM cameras don't have it.

Reply   Reply with quote   Complain
cctpix
Forum MemberPosts: 84
Like?
Re: SD14 vs SD15 image quality ?
In reply to John Brubaker, 11 months ago

I have both the '14 and '15 and I have mixed feelings about the assertion that the SD-15 doesn't have as much dynamic range as the SD-14.  I think that it (the SD-15) does, but it isn't in the same place as the range in the SD-14.

If you are going to take an analog signal from the sensor and then put it into the A/D converter you would do so with an analog amplifier.  On the SD-14, I'm sure that this gain is fixed in hardware and since it *is* fixed, a conservative designer would make absolutely certain that it would be unlikely to clip the A/D under any normal circumstances.  The problem with being too conservative is that you artificially reduce the quantization range (e.g. effective bit depth) and thus cause degradation of the images - particularly at higher ISOs.

The fact that the SD-14 does function at ISO-50 and it is roughly as "highlight-clip sensitive" at that ISO as the SD-15 at 100 ISO indicates to me that given the same sensor in both cameras, the gain of the post-sensor analog amplifier is probably somewhat higher on the SD-15 at ISO100 than the (fixed) gain of the SD-14.

The major implication of this is that the SD-14 has increasing tolerance of highlights as one increases the ISO - this being because the raw sensor data is always going to be the same for a given exposure (shutter speed, f-stop) no matter what the ISO setting.  The other implication is that as the ISO is increased, the effective bit depth of the raw data will also decrease.

The SD-15, on the other hand, increases the post-sensor analog gain with increasing ISO - and this means that the raw data is different as one increases ISO, even with the same exposure settings.  Because of this, the tolerance of highlights will not increase with increasing ISO, but more likely stay about the same.  (This might not be entirely true since at low ISOs the exposures are such that actual saturation of the sensor itself might occur.)   The implication here is that with increased post-sensor amplifier gain, you will not lose bit depth with increased ISO as you would with the SD-14.  Practically speaking, increased amplification will bring up the sensor noise - but it is better to deal with Gaussian-ish (analog) sensor noise than the quantization noise!  (In other words, the AFE with the high signal gain in the SD-15 more accurately records noise from the sensor whereas noise in the SD-14 is going to be a combination of sensor noise *and* quantization noise.)

In other words:  The SD-14 dynamic range is offset to favor the highlights - particularly at higher ISOs where the SD-15 dynamic range is offset to favor the shadows, but this doesn't really change at different ISOs.  What I *really* wished the SD-15 had was a way to turn the AFE's automatic gain control off - or, better yet, "offset" it so that I could decide for myself whether I wanted it to favor highlights or shadows.

What does this mean in practice?  When I was regularly using my SD-15 I had it set to EV -1 or -1.5 as the pictures that take tend to include elements that were much brighter than the subject.  Later on I frequently bracketed exposures when the situation allowed - something that was pretty painless to do on the SD-15 with its rather large buffer and coupled with the fact that large capacity memory cards are cheaper than ever!

(I discussed this a few years ago in more detail if you want to search for it...)

CT

Reply   Reply with quote   Complain
Keyboard shortcuts:
FForum MMy threads